Next Article in Journal
Water Use Efficiency and Economic Evaluation of the Hydroponic versus Conventional Cultivation Systems for Green Fodder Production in Saudi Arabia
Next Article in Special Issue
Deformation and Failure Laws of Surrounding Rocks of Coal Roadways under High Dynamic Load and Intelligent Prediction
Previous Article in Journal
Identification and Counting of Coffee Trees Based on Convolutional Neural Network Applied to RGB Images Obtained by RPA
Previous Article in Special Issue
Experimental Study on Permeability Evolution of Deep Coal Considering Temperature
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sustainability
Volume 15
Issue 1
10.3390/su15010821
sustainability-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Study on the Influence of Roadway Structural Morphology on the Mechanical Properties of Weakly Cemented Soft Rock Roadways

by
Yongli Liu
,
Jingtao Li
,
Yanwei Duan
*,
Tao Qin
and
Zhenwen Liu
Key Laboratory of Mining Engineering of Heilongjiang Province College, Heilongjiang University of Science and Technology, Harbin 150022, China
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(1), 821; https://doi.org/10.3390/su15010821
Submission received: 26 October 2022 / Revised: 30 November 2022 / Accepted: 2 December 2022 / Published: 2 January 2023
(This article belongs to the Special Issue Green and Scientific Design of Deep Underground Engineering)
Browse Figures
Review Reports Versions Notes

Abstract

:
We used the 11,303 return air roadway of the Hongqingliang coal mine as the engineering background for a study exploring the impact of the structural morphology of the roadway on the stress distribution characteristics and the stability of a weakly cemented soft-rock mine roadway. This work studies the evolution law of stress and deformation, and the plastic zone of weakly cemented soft-rock roadways with retaining the top or bottom coal seams. The results show that when retaining the top coal is replaced by the bottom coal, the high-stress zone of the vertical stress is reduced, the peak stress is decreased, and the stress concentration coefficient is slightly reduced from 1.67 to 1.64. The peak value of the vertical displacement of the roof of the shaft which was 78.4% of that of the top coal also decreases significantly, while the peak value of the vertical displacement of the floor, which was 1.37 times that of the top coal, increases. The equal area method was used to change the aspect ratio of the roadway. When the aspect ratio decreased from 1.38 to 0.88, the high-stress zone of the vertical stress was reduced, the stress peak decreased, and the stress concentration coefficient decreased from 1.8 to 1.75. The vertical displacement of the roof increased by 27.7% from 10.91 mm to 13.93 mm, and the vertical displacement of the floor increased by 15.2% from 6.60 mm to 7.60 mm. The plastic failure range was significantly reduced, particularly at the bottom corners. These findings show that structural morphology has a great influence on the floor heave of weakly cemented soft rock. Reasonable retention of the top or bottom coal and the aspect ratio of the roadway can prevent the deformation and failure of the roadway in weakly cemented soft rock.

1. Introduction

The weakly cemented soft rocks of the Triassic, Cretaceous, and Jurassic periods are widely distributed in Xinjiang, Gansu, Ningxia, and Western Inner Mongolia in the western regions of China [1,2,3]. Due to their low strength and easy weathering, they are easily softened and prone to disintegration after excavation and encountering water. The rock quality deteriorates rapidly, resulting in frequent engineering disasters, such as slope slides, large roofing, high spalling, and serious floor heave in the roadway. Therefore, the prevention and control of engineering disasters in weakly cemented soft rocks are urgent problems to be solved in western coal mining. From the perspective of disaster management [4,5,6], regulating the distribution of the stress field to control the damage to weakly cemented soft rock roadways is the simplest, most effective, and most economical method. Retaining the coal seams at the top or bottom and changing the roadway aspect ratio of the shaft will affect the distribution of the stress field. Therefore, it is important to analyze the reasonable layout of the roadway shape from the perspective of stress to prevent and control deformation and failure of weakly cemented soft rock roadways.
To explore the factors affecting stability and the deformation instability laws and how they apply to weakly cemented soft rock mine shaft roadways, scholars have used theoretical analysis, numerical simulation, on-site testing, and other methods. Zhao et al. [7] calculated an equation for elastic stress in the surrounding rock under the joint action of water and a non-uniform stress field. The authors put forth an implicit function calculation method of the plastic zone boundary based on the limit equilibrium method and analyzed the influence of the moisture field and the lateral pressure coefficient on the main partial stress and plastic zone range of the surrounding rock. Li [8] studied the influence of the depth of the coal seam and the lateral pressure coefficient on the deformation and failure characteristics of the surrounding rock and the distribution characteristics of the plastic zone and configured the deformation and instability law of weakly cemented soft rock roadways. Cai [9] explored the physical and mechanical properties of weakly cemented soft rock roadways, surrounding rock, roadway deformation characteristics, and a constitutive model of a roof of weakly cemented soft rock and revealed the roof instability mechanism of a weakly cemented soft rock roadway. Zhao et al. [10] analyzed the stability of surrounding rock after excavating a mine roadway when the water content of the weakly cemented strata was 2%, 5%, 10%, 15%, and 18%, respectively. Ru et al. [11] studied the deformation and failure law of weakly cemented soft rock roadways in close coal seams. Yuan [12] numerically simulated the influence law of elastic modulus, internal friction angle, cohesion, ground stress, lateral pressure coefficient, and support resistance on the displacement of the surrounding rock. Ma et al. [13] analyzed the effect of thickness and stiffness of a weak mudstone interlayer on the amount of roof subsidence using numerical calculation methods to determine the effect of thickness, stiffness, and strength of the weak mudstone interlayer on the deformation of weakly cemented soft rock roadways. In conclusion, there are many factors influencing the stability of the surrounding rock of weakly cemented soft rock roadways, mainly including the mechanical properties of the surrounding rock, the surrounding rock environment, and the surrounding rock roof structure, etc.
The roadway structural morphology is one of the important factors affecting the spatial mechanical distribution of roadways. Based on this, many scholars have analyzed the impact of roadway structural morphology on the stability of surrounding rock. Zhao et al. [14] studied the bearing structure of the surrounding rock of the roadway by theoretical analysis and numerical simulation given the geological characteristics of the surrounding rock of a weak and broken roadway and proposed a deep and shallow double bearing structure model. Sun et al. [15] regarded the surrounding rock and support of the roadway as a complex system and analyzed and studied the stability of the surrounding rock structure using the theory of dissipative structure. Ye et al. [16] used numerical simulation to analyze the deformation characteristics of a weak structure type when a roadway crossed the stratum and determined the specific support scheme. Zhang et al. [17] used numerical simulation to study the formation process of the layered structure of rock surrounding a roadway under dynamic disturbance and analyzed the influence of roadway depth, rock elastic modulus, etc., on its formation process. Du et al. [18] classified the rock mass structure and analyzed the stress characteristics and plastic failure characteristics of roadways with different structure types, thus obtaining the relationship between the rock mass structure type and the stability of the surrounding rock of roadways. Meng et al. [19] selected six kinds of roadways with different section shapes, such as rectangle, trapezoid, straight wall arch, horseshoe, oval, and circle, to conduct optimization research. Based on a FLAC3D simulation, the deformation characteristics of the surrounding rock and the distribution law of the surrounding rock plastic zone after excavation of these six typical roadways were studied, and the influence of different lateral pressure coefficients on them was analyzed. Li et al. [20] selected six kinds of roadway section shapes, namely rectangle, straight wall semicircle arch, horseshoe shape, three-centered arch, circle, and oval, to carry out optimization research and used numerical simulation software to analyze the plastic distribution of the surrounding rock and the distribution law of surrounding rock principal stress difference after tunnel excavation and concluded that the reasonable section shape under high-stress conditions was circular or oval. Zhang et al. [21] studied the stress distribution characteristics of the surrounding rock of a deep roadway with a large dip angle and designed the eccentric arc arch section by comprehensively considering the advantages of the semi-circular arch roadway and the trapezoidal roof. The engineering inspection judged that the support effect was good. Li et al. [22] analyzed the optimal shape of the roadway section under the condition of layered rock mass by using numerical simulation and pressure-balanced arch theory and recommended that for a roadway with arch caving and overall slip failure occurring in the roof, engineers should use a straight wall arch section, and for a roadway with wedge caving, engineers should use a pentagon section. By calculating the height of the fractured zone, Yang et al. [23] compared and analyzed the proper sectional shape of the roadway for upward mining. Through numerical simulation, they concluded that the surrounding rock stability of the roadway with a straight wall and semicircular arch section was the best, followed by the micro arch. They determined that the rectangle was the worst. In conclusion, the influence of roadway structural morphology on the stability of the surrounding rock is mainly reflected in the structure and section shape of the surrounding rock.
Based on the above research, scholars have carried out a wealth of research on the stability of weakly cemented soft rock and the structural morphology of the roadway and obtained fruitful research results, such as stability control technology of deep soft rock roadways [24,25,26], soft rock creep [27,28], water action characteristics of soft rock [29,30], and other issues. However, studies on the influence of roadway structure morphology on the mechanical properties of the weakly cemented soft rock are relatively rare. This work discusses the influence of top or bottom coal retention and the aspect ratio of the roadway on weakly cemented soft rock; analyzes the evolution law of stress, plastic zone, and deformation and determines the roadway structure form that conforms to the stability of the 11,303 return air roadway in the Hongqingliang coal mine. This work provides new ideas and practical experience for the prevention and control of the deformation and failure of weak cemented soft rock roadways.

2. Preliminary Analysis of the Deformation Characteristics of the 11,303 Return Airway in the Hongqingliang Coal Mine

2.1. Basic Overview of 11,303 Working Face of the Hongqingliang Coal Mine

The 11,303 working face is the second coal mining face in the Hongqingliang coal mine, which is located in the 3-1 panel of the first level. The upper No. 2 coal seam is not mined, and the lower No. 4 coal seam is not mined. The 11,303 working face layout is shown in Figure 1. The north of the 11,303 working face is the 11,301 working face goaf, the south is the 11,304 working face, the east is the 3-1 coal auxiliary transport roadway, and the west is the mine boundary. The 11,303 fully mechanized mining face is arranged along the coal seam, and the working face roadway is arranged along the coal seam strike. The length of the working face is 275 m, and the advancing length is 4279 m. A belt roadway, an auxiliary transportation roadway, a return air roadway, and a waist roadway are arranged in the fully mechanized mining face. The transportation roadway forms an interchange relationship with the 3-1 coal auxiliary transportation roadway and the 3-1 coal belt roadway through the belt head chamber and is connected with the 3-1 coal belt roadway. The geological structure of the working face is simple. The strata strike is 90~140° and dips south. Small folds and faults (the red part in Figure 1) in the eastern part of the working face are relatively developed. Affected by them, the local coal seam has waves and fluctuations; The coal seam is relatively stable, the roof and floor are relatively flat, the local uneven, the roof is relatively complete, and the cracks are not very developed.

2.2. Preliminary Analysis of the Deformation and Failure of the 11,303 Return Air Roadway in the Hongqingliang Coal Mine

Due to the influence of factors, such as large buried-depth, high ground stress, poor lithology, and rich floor water [31,32,33], in the 11,303 working face of the 3-1 coal seam in the Hongqingliang coal mine, serious floor heave occurred during the excavation process, with the maximum floor heave amount reaching 1.0 m. The rheological deformation of the roadway was serious, and the bulging part of the floor of the return air roadway was removed several times during excavation, as shown in Figure 2. In August 2020, after the temporary suspension of mining at the 11,303 working face, the bearing capacity of the roadway support was significantly reduced, and the deformation of the roadway was further aggravated, which led to the failure of the support body and coal wall caving, floor heave, and side shrinkage at the working face, which is very likely to induce roof and floor accidents and significantly increase the degree of safety risk [34,35]. Through the lithological analysis and mechanical properties, the return airway of the 11,303 working face of the Hongqingliang coal mine was to contain weakly cemented soft rock. Preliminary analysis of the serious floor heave in the return airway of the 11,303 working face showed that it was mainly due to water disintegrating the weak sandy mudstone floor, coupled with the strong mining impact of the rock surrounding the roadway under high stress and serious rheological deformation. This resulted in roadway deformation increasing sharply and obvious floor heave. When a roadway has serious floor heave, the commonly used rectification method is to remove the bulging part of the roadway floor; however, after some time, the floor will heave again, and the bulging part will again need to be removed. In this way, such repeated engineering leads to the continuous expansion and destruction of the entire roadway, which seriously affects the basic usage function of the roadway and affects normal production, increasing the cost of roadway maintenance.
The monitoring curve of the working resistance of an advanced single prop is shown in Figure 3, and the influence range of the advanced working resistance was about 58 m. During the excavation period, the 11,303 return air roadway of the Hongqingliang coal mine was constantly deformed by convergence, and the maximum amount of floor heave reached 1.6 m, the maximum amount of roof subsidence reached 1.2 m, and the maximum displacement of the two sides reached 0.8 m. The support system was seriously destabilized and repaired several times. For the deformation and failure of the roadway, the preliminary analysis found that the floor is sandy sandstone, which is a weak floor, and the floor is the release port for stress or energy under excavation unloading and disturbance. The floor therefore shows the most serious deformation response. The mining caused the leading support pressure of the single hydraulic support to increase, with the maximum reaching about 24 MPa. Through field observation, floor heave occurs repeatedly and becomes more and more serious. For this phenomenon, the main countermeasures are to increase the support strength of the two sides and the roof and remove the bulging part of the floor. However, these measures cannot achieve a complete solution.

2.3. Establishment of the 11,303 Return Airway Model in the Hongqingliang Coal Mine

The 11,303 return airway of the Hongqingliang coal mine was selected for a 3D numerical calculation model, as shown in Figure 4. Considering the stress boundary and influence range, the model size was 400 m × 200 m × 50 m, where the x-axis was the coal seam tendency, the y-axis was the coal seam direction, and the z-axis was the vertical direction. Plane z (represented by the organ in the figure) was intercepted in the middle of the coal seam. The 11,303 working face plane diagram is shown on the right.
According to the actual situation of the 11,303 working face of the Hongqingliang coal mine, the size of the roadway section is 5.5 m × 4.0 m (width ×height). The displacement constraint is applied around and at the bottom of the model, and 12.2 MPa stress is applied at the top of the model, which is equivalent to the self-weight of the overburdened rock. In a rock mechanics calculation [36,37], the calculation formula is σz = γh. Where, γ is the average unit weight of rock stratum, which is generally taken as 25 kN/m3; and h is the burial depth, 488 m. The horizontal stress of the rock layer is applied according to the field ground stress measurement results (σx = 17.94 MPa, σy = 10.18 MPa). The specific data of the coal rock parameters are calculated using the Mohr -Coulomb model as shown in Table 1.

3. Analysis of the Influence of a Retaining Roof or Bottom Coal on a Weakly Cemented Soft Rock Roadway

3.1. Design of a Retaining Roof or Bottom Coal of the Weakly Cemented Soft Rock Roadway

The coal thickness of the 11,303 working face of the Hongqingliang coal mine was 5 m, and the current mining height was 4 m. To ensure the stability of the roof, the mining method of retaining the top coal was used. To investigate the influence of retaining the roof or bottom coal on the surrounding rock of the roadway, the 11,303 return air roadway was used as the engineering background. Combined with geological conditions, according to the original plan to excavate along the floor of the coal seam, the thickness of retaining top coal was 1 m. If excavation was carried out along the roof, the thickness of the retaining bottom coal would be 1 m. The FLAC3D model diagram is shown in Figure 5.
The displacement constraint was taken around and at the bottom of the model, and a stress of 12.2 MPa was applied at the top of the model, which was consistent with the gravity of the upper overburden; the specific parameters are shown in Table 1. The Mohr-Coulomb constitutive model was used to explore the stress characteristics, deformation characteristics, and plastic zone distribution law of the surrounding rock in the weakly cemented soft rock roadway.
If the top coal is retained, it means the upper part is the weak roof, and the control of the roof is the top priority for roadway stability. Conversely, if the bottom coal is retained, it means the lower part is the weak floor, and the control of the floor is the key to the roadway stability control. Because the rock of the floor is weakly cemented soft rock, the strength is relatively low. Whether the top coal or bottom coal is retained, the floor is one of the difficult points of control. The low strength region of the surrounding rock will release stress and deform, and also the location of large deformation and failure, so more attention should be paid to the surrounding rock control.

3.2. Stress Characteristics of Surrounding Rock of Retaining the Top or Bottom Coal in the Weakly Cemented Soft Rock Roadway

Retaining the top or bottom coal will affect the stress distribution of the surrounding rocks in the weakly cemented soft rock roadway. This is, mainly because the coal body has lower strength compared with the rock body, and the roof and floor cannot present stress concentration, resulting in a slower increase in the internal surrounding pressure and lower overall strength of the surrounding rocks. As shown in Figure 6, the stress distribution characteristics of retaining the top or bottom coal were consistent, i.e., the two sides show a “binaural” stress concentration, which reflects the excavation unloading, and the stress was transferred to the interior. The roadway as a whole showed an oval low-pressure area, the roof and floor presented a more obvious pressure relief effect, while the two sides did not demonstrate a pressure relief area.
Figure 6 shows the vertical stress cloud diagram of the surrounding rock of the roadway under the conditions of retaining the top or bottom coal. The vertical stress distribution pattern of the surrounding rock of retaining the top or bottom coal of the roadway was the same, the two sides of the roadway were high-stress areas, and the two sides spread to both sides in an elliptical pattern. The roof and floor were low-stress areas and spread to both sides in a semi-circular pattern, and finally transitioned to the original rock stress area. The distribution of the stress area of retaining the top or bottom coal of the roadway were slightly different: in terms of the high-stress area of the two sides, the high-stress area of the retaining the top coal for the roadway was slightly larger; for the low-stress area of the roof and floor of the roadway, the difference was not large. In rock mechanics, the ratio of secondary stress to primary stress after the roadway opening is usually defined as the stress concentration coefficient at this point [38,39,40]. In this work, the stress concentration coefficient refers to the stress concentration coefficient at the peak stress. The stress peaks of the different retaining coal methods for the roadway were different, the high-stress peak of retaining the top coal of the roadway is 20.41 MPa, and the stress concentration coefficient was 1.67, retaining the bottom coal of the roadway was 20.03 MPa, and the stress concentration coefficient was 1.64. Therefore, combined with the change of peak stress and high-stress area, it can be seen that the stability of the surrounding rock of the roadway with bottom coal was better, which indicates that the retaining coal method can improve the stress environment of the surrounding rock.

3.3. Deformation Characteristics of the Surrounding Rock of Retaining the Top or Bottom Coal in the Weakly Cemented Soft Rock Roadway

Figure 7 shows the vertical displacement cloud diagram of the surrounding rocks for the different methods of coal retention. The deformation of the roof was larger when the top coal was retained, and the deformation of the floor was larger when the bottom coal was retained, which reflects the characteristics of energy release of the surrounding rock in the weak area. When the top coal was retained, the influence range of the roof deformation was larger than that of the bottom coal case, and vice versa, the influence range change pattern was also consistent.
From Figure 7, it can be seen that after the roadway was excavated and stabilized, the vertical displacement mainly occurred in the roof and floor of the roadway, and different methods of coal retention had different effects on the displacement produced by the roadway’s surrounding rock, mainly on the relatively weaker coal seam. When retaining the top coal, the influence range of vertical displacement of the roof was larger, the roof subsidence was 15.95 mm, and the floor heave was 8.26 mm; when retaining the bottom coal, the influence range of vertical displacement of the floor was larger, the roof subsidence was 12.50 mm, which is 78.4% of that of retaining top coal, and the floor heave was 11.31 mm, which was 1.37 times of that of retaining the top coal, indicating that the floor was more likely to deform when retaining bottom coal. It was not conducive to floor control.

3.4. The Distribution of Plastic Zone of the Surrounding Rock of Retaining the Top or Bottom Coal in the Weakly Cemented Soft Rock Roadway

Figure 8 shows the distribution of the plastic area of the surrounding rocks of retaining the top or bottom coal. Regardless of whether the top coal or bottom coal was retained, the overall failure pattern of the roadway still showed the “Ω” pattern. The damage range of the roof of retaining top coal was larger than that of retaining bottom coal, especially in the two corners of the roof of the roadway. On the contrary, the damage range of the floor of retaining the bottom coal was larger than that of retaining the top coal, and the main difference was in the range of vertical area.
Figure 8 shows the distribution of the plastic zone of retaining the top or bottom coal. (1) The different methods of retaining the coal surrounding the rock plastic-zone damage were the same. The roof and floor were tensile failures, and the range of roadway sides and bottom corners was a shear failure. From the viewpoint of the damage range, the shear failure had a greater impact range. (2) Compared with retaining the top coal, the plastic failure area of retaining the bottom coal range was slightly smaller. The failure range of the roof and bottom corners was significantly smaller. This was because the roof strength was significantly improved by the retaining the bottom coal, and the roof stability ensured the stress transfer to the deep surrounding rock, thus improving the overall stability of the roadway.

4. Analysis of the Influence of the Aspect Ratio of the Roadway on a Weakly Cemented Soft Rock Roadway

4.1. Determination of the Aspect Ratio of the Weakly Cemented Soft Rock Roadway

Based on the above research, the simulation of retaining coal adopts the form of retaining the bottom coal. FLAC3D was used to establish the numerical model, and the current cross-sectional size of the upper and lower chute roadway was 4.0 m × 5.5 m. According to the principle of the equal area [41,42,43], the influence of different aspect ratios on the stability of the roadway’s surrounding rock was explored by appropriately changing the aspect of the roadway. Different aspect ratios of the scheme of the roadway are shown in Table 2.
Fixed constraints were applied around the model and at the bottom, and the equivalent load of 12.2 MPa was applied at the top of the model. Rock mechanical parameters are shown in Table 1. The Mohr-Coulomb constitutive model was used to deeply analyze the stress characteristics, deformation characteristics, and plastic zone distribution law of the roadway’s surrounding rock under different aspect ratios of the roadway.

4.2. Stress Characteristics of the Surrounding Rock with Different Aspect Ratios in the Weakly Cemented Soft Rock Roadway

Figure 9 shows the vertical stress cloud diagram of the surrounding rocks in different aspect ratios of the roadway. The overall change pattern and characteristics were consistent, which shows that changing the aspect ratio of the roadway did not essentially change the stress distribution, but the change of the peak value shows that changing the aspect ratio of the roadway could change the stress concentration degree of the surrounding rocks to a certain extent, thus regulating the stability of the weakly cemented soft rock roadway.
After the roadway was excavated and stabilized, the two sides of the roadway are the high-stress area and the roof and floor are the low-stress areas, and the dividing line between the high and low-stress areas is the top and bottom corners of the roadway. With the increase in the roadway aspect ratio, the high-stress concentration area was slightly increased, the peak stress increased from 21.38 MPa to 21.90 MPa, and the concentration coefficient increased from 1.75 to 1.80. The range of the low-stress area in the roof and floor of the roadway increased significantly. When the aspect ratio of the roadway was smaller, the high-stress concentration area of the roadway surrounding rock was smaller and the stress peak is smaller, and the roof and floor are compressive stresses which were more favorable to the stability of the roadway’s surrounding rock.

4.3. Deformation Characteristics of the Surrounding Rock with Different Aspect Ratios in the Weakly Cemented Soft Rock Roadway

To explore the deformation characteristics of the weakly cemented soft rocks under different aspect ratios, the vertical displacement law of surrounding rocks with aspect ratios ranging from 0.88 to 1.38 was analyzed.
Figure 10 shows the vertical displacement cloud diagrams of surrounding rocks with different aspect ratios of the roadway. After the roadway was excavated and stabilized, vertical displacement mainly occurred at the roof and floor of the roadway. The top and bottom parts of the roadway showed the “equipotential line” of local reduction, and the top two sides corners and the lower two bottom corners of the roadway show the trend of large deformation. Regardless of the aspect ratio, the overall trend was the same, which means that the focus of rectangular roadway management is the four corner areas. From the deformation trend, the anchor rod and anchor cable support should be carried out along the 45° side angle.
When the aspect ratio of the roadway was 0.88, the maximum displacement of the roadway roof was 10.91 mm, which was located in the middle region of the roof, and the maximum displacement of the floor was 6.60 mm, which was located in the middle region of the floor. With the increase in aspect ratio, the displacement range of the roof and floor becomes larger and the peak of vertical displacement also increased. The vertical displacement of the roof increased from 10.91 mm to 13.93 mm, an increase of 27.7%, and the vertical displacement of the floor increased from 6.60 mm to 7.60 mm, an increase of 15.2%. The deformation changes of the two sides were small.
It can be seen in Figure 10 that with the increase of the aspect ratio of the roadway, the influence range of the floor deformation increased, and its value also shows the trend of growth, and the influence range of the present deformation of the roof shows the trend of decreasing, but the roof roadway displacement shows the trend of increasing, which indicates that for a roadway with a larger aspect ratio, the roof needs to control the local area to be able to achieve the control of the surrounding rock, and the area and range of the floor control are larger. When the aspect ratio of the roadway was small, the vertical displacement of the roof and floor of the roadway was also small. In other words, when the roadway height is satisfied, the roadway width can be appropriately reduced, which is conducive to the stability of the roof and floor of the roadway.

4.4. Plastic Zone Distribution of the Surrounding Rock with Different Aspect Ratios in the Weakly Cemented Soft Rock Roadway

To explore the failure range of weakly cemented soft rocks under different aspect ratios, the plastic zone variation law of the surrounding rocks with aspect ratios between 0.88 and 1.38 were analyzed, focusing on the overall fracture morphology and partial fracture range for discussion and analysis.
Figure 11 shows the distribution of the plastic zone of surrounding rocks with different aspect ratios. No matter how the aspect ratio changed, the overall roadway still showed “Ω” form, i.e., the vertical failure range of the roof was similar, but the horizontal failure range gradually increased. Especially in the two corners, the two sides of the roadway showed obvious convex in an arc shape, i.e., the failure range in the middle of the roadway was larger, and the upper and the lower parts of the roadway shows a decreasing trend. The two bottom corners of the roadway were the areas with the greatest failure depth and range of the surrounding rock, and the failure depth of the floor showed an increasing trend.
The failure of the roadway’s surrounding rock was mainly shear failure and tensile failure. Shear failure mainly occurred in the top and bottom corners of the roadway and the two sides of the roadway, and tensile failure mainly occurred in the roof and floor of the roadway. With the increase of the aspect ratio of the roadway, the plastic failure zone increased, especially in the top and bottom corners. As the width of the roadway increased, the pressure released from the roof and floor due to roadway excavation was transferred to the two sides, causing shear failure at the top and bottom corners. When the roadway aspect ratio was small, it was conducive to the stability of the roadway’s surrounding rock.

5. Discussion

5.1. Establishment of Numerical Model and Analysis of Results

The numerical model of working face 11,303 in the Hongqingliang coal mine established in this work was based on the site geological conditions and engineering layout. The scope of the whole numerical model research was different from that of the roadway’s surrounding rock stability research. In future research, a numerical model should be established for roadway-size with scope for small-scale research.
For the numerical simulation results, the research was not deep enough. For example, for the analysis of the plastic failure areas, visual comparison and overview was only carried out in the visual range. Furthermore, statistical methods were used to provide statistics on the plastic failure types and the number of plastic failures in the plastic failure areas, to conduct the quantitative analysis. In another example, for the analysis of high-stress areas, only the peak stress and stress concentration factor were analyzed, which can analyze the area and change of high-stress areas.

5.2. Theoretical Analysis and Support

The analysis method in this work mainly relied on numerical simulation, and was lacking a theoretical analysis. For the theoretical basis of retaining the top or bottom coal, it remained in the methodology and did not establish a relevant mechanical model for analysis. A mechanical model should be established to obtain an analytical solution from the theory. By comparing the analytical solution with the simulated solution, the correctness of the data can be verified from several perspectives. In a follow-up study, a mechanical model of the coal retention mode should be studied.

5.3. On-Site Monitoring and Application

There was a lack of on-site monitoring data and insufficient analysis of on-site data. For the description of the current situation of the roadway such as the high-stress action, the serious rheological deformation, and the roadway deformation increase, there was only a qualitative description available and not a quantitative analysis. For detailed analysis, comprehensive and detailed on-site monitoring should be carried out for the return air roadway of working face 11,303.
This work analyzes the influence of the coal retention mode and roadway aspect ratio on roadway mechanical properties, but the guiding role of the on-site roadway needs to be verified on-site, and the feasibility of the method should be verified through long-term on-site monitoring.

6. Conclusions

The structural morphology of the roadway affects the distribution of the stress field and then affects the stability of the roadway. Taking the Hongqingliang weakly consolidated soft rock roadway as the research object, this paper analyzes the distribution characteristics of surrounding rock stress, and deformation and plastic zone under the conditions of coal retaining at the top and bottom of return roadway 11,303 and the width/height ratio of roadway, and draws the following conclusions:
(1)
Changing the method of retaining the top or bottom coal can improve the stability of the surrounding rock. When the retaining of the top coal is changed to retaining of the bottom coal, the high-stress zone of the surrounding rock decreases, the peak stress decreases and the stress concentration coefficient decreases from 1.67 to 1.64. The peak vertical displacement of the roof decreases significantly, which is 78.4% of that of the top coal, while the peak vertical displacement of the floor increases, which is 1.37 times that of the top coal. The plastic failure range is obviously reduced, especially at the bottom corners. The surrounding rock’s stability due to retaining the bottom coal is better than that of the top coal.
(2)
The stability of the surrounding rock can be improved by changing the section properly. When the section aspect ratio of the roadway decreases from 1.38 to 0.88, the high-stress zone of surrounding rock decreases, its peak value decreases, and the stress concentration coefficient decreases from 1.8 to 1.75. The vertical displacement of the roof increases by 27.7% from 10.91 mm to 13.93 mm, and the vertical displacement of the floor increases by 15.2% from 6.60 mm to 7.60 mm. The plastic failure range is significantly reduced, particularly at the bottom corners. When the ratio of width to height is small, the surrounding rock stability is the best.
(3)
In the structural morphology of the roadway, the deformation of the floor of the weakly cemented soft rock is larger when the bottom coal is retained compared with the top coal, and the vertical displacement of the floor increases from 6.60 mm to 7.60 mm with the increase of the roadway aspect ratio, which indicates that the structural morphology of the roadway has a greater influence on the floor heave of weakly cemented soft rock roadway, and the reasonable retaining of the top or bottom coal and roadway aspect ratio can reduce the deformation of the weakly cemented soft rock roadway.
(4)
This work adopts the method of combining a numerical simulation with field monitoring to discuss the stability of the roadway’s surrounding rock with different structural morphology. However, there are some problems, such as the lack of theoretical analysis, the lack of quantitative analysis in the numerical simulation and the lack of comprehensive field monitoring data, which should be supplemented in subsequent studies.

Author Contributions

Conceptualization, Y.L.; validation, J.L.; formal analysis and investigation, T.Q. and Y.D.; data curation, Y.L., J.L. and T.Q.; writing—original draft preparation, J.L. and Y.D.; writing—review and editing, J.L. and Z.L.; supervision, Y.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Scientific and Technological Key Project of “Revealing the List and Taking Command” in Heilongjiang Province: Study on geological model and ventilation model of intelligent mining in extremely thin coal seam (2021ZXJ02A03).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Li, Y.; Ma, C.; Zhang, L.Y.; Li, B. Influence Research for Softening and Swelling of Weakly Cemented Soft Rock on the Stability of Surrounding Rock in Roadway. Geofluids 2022, 2022, 6439277. [Google Scholar] [CrossRef]
  2. Zhao, Z.H.; Lv, X.Z.; Wang, W.M.; Tan, Y.L. Damage evolution of bi-body model composed of weakly cemented soft rock and coal considering different interface effect. SpringerPlus 2016, 5, 292. [Google Scholar] [CrossRef] [Green Version]
  3. Qiao, W.G.; Wei, J.Z.; Lin, D.G.; Wang, L.H.; Cheng, S.B. The Deformation Failure Mechanism of Very Weakly Cemented Soft Rock Formed During Jurassic-Cretaceous Period in Roadways. J. Shandong Univ. Sci. Technol. (Nat. Sci.) 2013, 32, 1–6. [Google Scholar] [CrossRef]
  4. Tahir, A.A.; Siddique, U.; Waheed, U.; Rafi, U.; Raja, U.S.; Abdullah, M.; Alamgir, K.; Muhammad, F.J.; Anwarud, D. Development and Application of Models for Landslide Hazards in Northern Pakistan. Sustainability 2022, 14, 194. [Google Scholar]
  5. Ma, Z.J.; Qin, S.W.; Cao, C.; Lv, J.F.; Li, G.J.; Qiao, S.S.; Hu, X.Y. The Influence of Different Knowledge-Driven Methods on Landslide Susceptibility Mapping: A Case Study in the Changbai Mountain Area, Northeast China. Entropy 2019, 21, 372. [Google Scholar] [CrossRef] [Green Version]
  6. Kang, Y.S.; Geng, Z.; Liu, Q.S.; Liu, B.; Zhu, Y.G. Research progress on support technology and methods for soft rock with large deformation hazards in China. Rock Soil Mech. 2022, 43, 2035–2059. [Google Scholar] [CrossRef]
  7. Zhao, Z.H.; Yang, P.; Zhang, M.Z.; Lyu, X.Z.; Chen, S.J. Analysis of surrounding rock stability of weakly cemented soft rock roadway under the combined action of water environment and non-uniform ground pressure. J. Min. Saf. Eng. 2022, 39, 126–135. [Google Scholar] [CrossRef]
  8. Li, T.L. Study on deformation and instability law of weakly cemented soft rock roadway based on UDEC simulation. J. Coal 2021, 30, 9–12+16. [Google Scholar]
  9. Cai, J.L. Deformation and Instability Mechanism of Jurassic Weakly Cemented Soft Rock Roadway and Its Application. Anhui University of Science and Technology. 2020. Available online: https://kns.cnki.net/kcms/detail/detail.aspx?doi=10.26918/d.cnki.ghngc.2020.000420&dbcode=CDFD (accessed on 25 October 2022).
  10. Zhao, W.S.; Liang, W.; Wang, H.; Kou, S. The influence of formation water content on the stability of surrounding rock in weakly cemented soft rock roadway: Taking Wujianfang Xiyi Coal Mine in Inner Mongolia as an example. China Min. 2020, 29, 154–159. [Google Scholar]
  11. Ru, W.K.; Hu, S.C.; Ning, J.G.; Wang, J.; Gu, Q.H.; Guo, Y.; Zuo, J. Study on the Rheological Failure Mechanism of Weakly Cemented Soft Rock Roadway during the Mining of Close-Distance Coal Seams: A Case Study. Adv. Civ. Eng. 2020, 2020, 8885849. [Google Scholar] [CrossRef]
  12. Yuan, G.M.; Zhang, C.P. Numerical simulation study on influence factors of stability of weakly cemented soft rock roadway. J. North China Inst. Sci. Technol. 2020, 17, 53–60+100. [Google Scholar]
  13. Ma, Q.; Zhao, Z.H.; Gao, X.J.; Chen, S.J.; Tan, Y.L. Numerical Survey on the Destabilization Mechanism of Weakly Cemented Soft Rock Roadway Considering Interlayer Effect. Geotech. Geol. Eng. 2019, 37, 95–105. [Google Scholar] [CrossRef]
  14. Zhao, G.M.; Zhang, X.B.; Wang, C.; Meng, X.R. Mechanical analysis and numerical simulation for deep and shallow bearing structures of soft and broken roadway surrounding rock. J. China Coal Soc. 2016, 41, 632–1642. [Google Scholar] [CrossRef]
  15. Sun, G.Y.; Ma, Y.D. Dissipative structure of system stability for roadway surrounding rock and support in mine. J. Heilongjiang Inst. Sci. Technol. 2007, 3, 169–172. [Google Scholar]
  16. Ye, W.D.; Xu, Y.; Li, Y.; Guo, P.; Cai, S.H. Weak Structure of Surrounding Rock and Support Technology in Inclined Roadway Crossing Coal Seam. Saf. Coal Mines 2015, 46, 221–224. [Google Scholar] [CrossRef]
  17. Zhang, X.C.; Lu, A.H.; Wang, J.Q. Numerical simulation of layer-crack structure of surrounding rock and rockburst in roadway under dynamic disturbance. Chin. J. Rock Mech. Eng. 2006, S1, 3110–3114. [Google Scholar]
  18. Du, D.J.; Niu, S.Q. Study on Correlation Between Rock Structure Type and Stability of Surrounding Rock Along Mine Roadway. Coal Eng. 2014, 46, 87–89+92. [Google Scholar]
  19. Meng, Q.B.; Han, A.J.; Qiao, W.G.; Lin, D.G.; Wei, L.C. Numerical Simulation of Cross-Section Shape Optimization Design of Deep Soft Rock Roadway Under High Stress. J. Min. Saf. Eng. 2012, 29, 650–656. [Google Scholar]
  20. Li, G.C.; Zhang, N.; Wang, C.; Zhang, N.C.; Li, B.Y. Optimizing the Section Shape of Roadways in High Stress Ground by Numerical Simulation. J. China Univ. Min. Technol. 2010, 39, 652–658. [Google Scholar]
  21. Zhang, J.P.; Liu, L.M.; Liu, C.X.; Zhao, Y.P.; Sun, D.L.; Shao, J. Cross-section shape and coupling support of deep and large-inclined coal and rock roadway. J. Cent. South Univ. (Sci. Technol.) 2021, 52, 4074–4087. [Google Scholar]
  22. Li, M.R.; Jia, K.Y.; Tan, B.H.; Liang, B.; Zhang, Z.G.; Hu, Y.P. Study on the Preferred Section Shape and Support Method for Roadway in Layered Rock Mass. Ming R D 2022, 42, 101–107. [Google Scholar] [CrossRef]
  23. Yang, S.L.; Liu, C.Y.; Li, M.; Liu, Y.; Xu, J.M.; Yue, H. Determination of roadway cross-section shape in upward mining of Yangchangwan Coal Mine. Coal Eng. 2022, 54, 5–11. [Google Scholar]
  24. Zhao, C.X.; Li, Y.M.; Liu, G.; Meng, X.R. Mechanism analysis and control technology of surrounding rock failure in deep soft rock roadway. Eng. Fail. Anal. 2020, 115, 104611. [Google Scholar] [CrossRef]
  25. Yang, S.Q.; Chen, M.; Jing, H.W.; Chen, K.F.; Meng, B. A case study on large deformation failure mechanism of deep soft rock roadway in Xin’An coal mine, China. Eng. Geol. 2017, 217, 89–101. [Google Scholar] [CrossRef]
  26. Huang, Z.K.; Zhang, D.M.; Pitilakis, K.; Tsinidis, G.; Huang, H.W.; Zhang, D.M.; Argyroudis, S. Resilience assessment of tunnels: Framework and application for tunnels in alluvial deposits exposed to seismic hazard. Soil Dyn. Earthq. Eng. 2022, 162, 107456. [Google Scholar] [CrossRef]
  27. Wang, W.M.; Gao, X.; Jing, J.D.; Liu, C.L.; Zhou, J.H. Study on Roof Bolting with Anchor and Wire Mesh Coupling Support Technology in Weakly Consolidated Soft Rock Roadway. Coal Sci. Technol. 2014, 42, 23–26. [Google Scholar] [CrossRef]
  28. Wang, W.M.; Zhao, Z.H.; Wang, L. Elastic-plastic damage analysis for weakly consolidated surrounding rock regarding stiffness and strength cracking. J. Min. Saf. Eng. 2013, 30, 679–685. [Google Scholar]
  29. Li, G.C.; Jiang, Z.H.; Lv, C.X.; Huang, C.; Chen, G.; Li, M.Y. Instability mechanism and control technology of soft rock roadway affected by mining and high confined water. Int. J. Min. Sci. Technol. 2015, 25, 573–580. [Google Scholar] [CrossRef]
  30. Li, H. Research on Control Mechanism and Application of Weakly Cemented Soft Rock Roadway with Alkaline Water-Enriched. China University of Mining and Technology. 2020. Available online: https://kns.cnki.net/kcms/detail/detail.aspx?doi=10.27623/d.cnki.gzkyu.2020.000489&dbcode=CDFD (accessed on 25 October 2022).
  31. Zhang, W.; Yang, F.Q.; Cai, L.S.; Zhang, C.; Yu, F.H.; Li, G.; Gao, X.P. Research on Support of Anchor Net in Weak Cemented Coal Roadway in Hongqingliang Coal Mine. Saf. Coal Mines 2018, 49, 45–49. [Google Scholar] [CrossRef]
  32. Rong, H.; Han, Y.L.; Zhang, H.W.; Xin, J.X.; Cao, Y.; Lan, T.W. Characteristics of in-situ stress field and stability analysis of roadway in Hongqingliang coal mine. Coal Geol. Explor. 2020, 48, 144–151. [Google Scholar]
  33. Zhang, X.D.; Yin, Z.G.; Peng, W.; Yuan, S.L. Reinforcement and Supporting Technique for Soft Rock Roadway Passing through Fault Fracture Zone in Hongqingliang Coal Mine. Met. Mine 2017, 9, 60–65. [Google Scholar]
  34. Lai, X.P.; Xu, H.C.; Shan, P.F.; Kang, Y.L.; Wang, Z.Y.; Wu, X. Research on Mechanism and Control of Floor Heave of Mining-Influenced Roadway in Top Coal Caving Working Face. Energies 2020, 13, 381. [Google Scholar] [CrossRef] [Green Version]
  35. Wang, K.; Huang, Y.L.; Gao, H.D.; Zhai, W.; Qiao, Y.F.; Li, J.M.; Ouyang, S.Y.; Li, W. Recovery Technology of Bottom Coal in the Gob-Side Entry of Thick Coal Seam Based on Floor Heave Induced by Narrow Coal Pillar. Energies 2020, 13, 3368. [Google Scholar] [CrossRef]
  36. Song, D.Z.; He, X.Q.; Wang, E.Y.; Li, Z.L.; Wei, M.H.; Mu, H.W. A dynamic ejection coal burst model for coalmine roadway collapse. Int. J. Min. Sci. Technol. 2019, 29, 557–564. [Google Scholar] [CrossRef]
  37. Kang, H.P.; Lin, J.; Fan, M.J. Investigation on support pattern of a coal mine roadway within soft rocks—A case study. Int. J. Coal Geol. 2015, 140, 31–40. [Google Scholar] [CrossRef]
  38. Liu, Y.Z.; Liu, J.; Hu, B.; Zhang, K.; Wu, E.Q.; Li, W. Parameter Determination of Bolt Support for Cross Roadway Based on Mean Stress Concentration Factor of Surrounding Rock. Met. Mine 2018, 7, 32–37. [Google Scholar] [CrossRef]
  39. Hu, X.Y.; Zhang, H.L.; Wang, L.G. Analysis on Stress Concentration Factors of roadway Surrounding Rock Affected by Cross Mining. Chin. J. Undergr. Space Eng. 2015, 11, 658–664. [Google Scholar]
  40. Ma, Q.; Zhang, Y.D.; Gao, L.S.; Li, Z.X.; Song, G.Y.; Zheng, Y. The Optimization of Coal Pillars on Return Air Sides and the Reasonable Horizon Layout of Roadway Groups in Highly Gassy Mines. Sustainability 2022, 14, 9417. [Google Scholar] [CrossRef]
  41. Song, H.T. Numerical Analysis and Experimental Research on Temperature Field of Surrounding Rock Under Mine Wind Temperature Periodic Change. China University of Mining and Technology. 2016. Available online: https://kns.cnki.net/kcms/detail/detail.aspx?FileName=1016282378.nh&DbName=CDFD2017 (accessed on 25 October 2022).
  42. Fu, Q.; Yang, K.; He, X.; Liu, Q.J.; Wei, Z.; Wang, Y. Destabilization Mechanism and Stability Control of the Surrounding Rock in Stope Mining Roadways below Remaining Coal Pillars: A Case Study in Buertai Coal Mine. Processes 2022, 10, 2192. [Google Scholar] [CrossRef]
  43. Shan, R.L.; Liu, W.J.; Li, G.Z.; Liang, C.; Shi, S.G.; Chen, Y.; Zhang, S.P. Experimental Study on the Shear Mechanical Properties of Anchor Cable with C-Shaped Tube. Sustainability 2022, 14, 9616. [Google Scholar] [CrossRef]
Sustainability 15 00821 g001 550
Figure 1. The 11,303 working face roadway layout.
Figure 1. The 11,303 working face roadway layout.
Sustainability 15 00821 g001
Sustainability 15 00821 g002 550
Figure 2. Characteristics of floor heave of the 11,303 return air roadway in the Hongqingliang coal mine: (a) overall floor heave; (b) local floor heave.
Figure 2. Characteristics of floor heave of the 11,303 return air roadway in the Hongqingliang coal mine: (a) overall floor heave; (b) local floor heave.
Sustainability 15 00821 g002
Sustainability 15 00821 g003 550
Figure 3. Working resistance monitoring curve of advanced single prop in the 11,303 working face.
Figure 3. Working resistance monitoring curve of advanced single prop in the 11,303 working face.
Sustainability 15 00821 g003
Sustainability 15 00821 g004 550
Figure 4. Calculation model of the 11,303 working face in the Hongqingliang coal mine.
Figure 4. Calculation model of the 11,303 working face in the Hongqingliang coal mine.
Sustainability 15 00821 g004
Sustainability 15 00821 g005 550
Figure 5. Model diagram of different roadway retaining methods. (a) retaining the top coal, (b) retaining the bottom coal.
Figure 5. Model diagram of different roadway retaining methods. (a) retaining the top coal, (b) retaining the bottom coal.
Sustainability 15 00821 g005
Sustainability 15 00821 g006 550
Figure 6. Vertical stress cloud diagram under retained top coal and bottom coal conditions. (a) retaining the top coal, (b) retaining the bottom coal.
Figure 6. Vertical stress cloud diagram under retained top coal and bottom coal conditions. (a) retaining the top coal, (b) retaining the bottom coal.
Sustainability 15 00821 g006
Sustainability 15 00821 g007 550
Figure 7. Vertical displacement cloud diagram of different coal retention methods. (a) retaining the top coal, (b) retaining the bottom coal.
Figure 7. Vertical displacement cloud diagram of different coal retention methods. (a) retaining the top coal, (b) retaining the bottom coal.
Sustainability 15 00821 g007
Sustainability 15 00821 g008 550
Figure 8. Plastic zone distribution of surrounding rock under different coal retention methods. (a) retaining the top coal, (b) retaining the bottom coal.
Figure 8. Plastic zone distribution of surrounding rock under different coal retention methods. (a) retaining the top coal, (b) retaining the bottom coal.
Sustainability 15 00821 g008
Sustainability 15 00821 g009 550
Figure 9. Vertical stress nephogram of surrounding rock in different roadway aspect ratios. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Figure 9. Vertical stress nephogram of surrounding rock in different roadway aspect ratios. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Sustainability 15 00821 g009
Sustainability 15 00821 g010 550
Figure 10. Vertical displacement cloud diagrams of surrounding rock with different aspect ratios of the roadway. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Figure 10. Vertical displacement cloud diagrams of surrounding rock with different aspect ratios of the roadway. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Sustainability 15 00821 g010
Sustainability 15 00821 g011 550
Figure 11. Distribution of plastic zone of surrounding rock with a different aspect ratio of the roadway. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Figure 11. Distribution of plastic zone of surrounding rock with a different aspect ratio of the roadway. (a) aspect ratio 0.88, (b) aspect ratio 0.96, (c) aspect ratio 1.04, (d) aspect ratio 1.14, (e) aspect ratio 1.38.
Sustainability 15 00821 g011
Table
Table 1. Table of mechanical parameters of rock strata.
Table 1. Table of mechanical parameters of rock strata.
Lithologic CharactersBulk Modulus
/GPa		Shear Modulus
/GPa		Internal Cohesion
/MPa		Internal Friction Angle/°Tensile Strength
/MPa		Density
/(kg/m3)
Conglomerate12.2210.792.5423.62531
Medium sandstone3.32.54.0371.22614
Conglomerate10.5810.022.1403.12637
Sandy mudstone2.562.362.16360.752538
Fine sandstone11.018.523.2421.292764
Coal4.912.011.25320.151400
Mudstone9.977.351.2320.582698
Sandy mudstone5.124.732.45402.012639
Sandy mudstone3.162.792.32381.652576
Coarse sandstone4.22.95.0341.52674
Table
Table 2. Different aspect ratios of the scheme of the roadway.
Table 2. Different aspect ratios of the scheme of the roadway.
Aspect Ratio0.880.961.041.141.38
Width/m4.44.64.85.05.5
Height/m5.04.84.64.44.0
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Liu, Y.; Li, J.; Duan, Y.; Qin, T.; Liu, Z. Study on the Influence of Roadway Structural Morphology on the Mechanical Properties of Weakly Cemented Soft Rock Roadways. Sustainability 2023, 15, 821. https://doi.org/10.3390/su15010821

AMA Style

Liu Y, Li J, Duan Y, Qin T, Liu Z. Study on the Influence of Roadway Structural Morphology on the Mechanical Properties of Weakly Cemented Soft Rock Roadways. Sustainability. 2023; 15(1):821. https://doi.org/10.3390/su15010821

Chicago/Turabian Style

Liu, Yongli, Jingtao Li, Yanwei Duan, Tao Qin, and Zhenwen Liu. 2023. "Study on the Influence of Roadway Structural Morphology on the Mechanical Properties of Weakly Cemented Soft Rock Roadways" Sustainability 15, no. 1: 821. https://doi.org/10.3390/su15010821

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop