True Triaxial Test and Research into Bolting Support Compensation Stresses for Coal Roadways at Different Depths

Abstract

During the excavation and support construction process used in coal mine roadways, the stress path is the unloading of in situ stress and the compensation of support stress. The 150 mm × 150 mm × 150 mm coal mass samples were obtained in situ underground and prepared, the true triaxial loading–unloading–confining pressure restoring test method was used, and the mechanical response and deformation failure evolution characteristics of the coal seam during the excavation and support process of the shallow, medium depth, and deep coal roadways in the coal mine were simulated and studied. Based on the distribution law of the bolt and cable support stress field, the support compensation stress required for the stability of the surrounding rock after the excavation of the coal roadway with different burial depths was determined, and the corresponding roadways’ surrounding rock control technologies were proposed. This study’s results indicate that the compensation stress required for support in shallow coal roadways (with a burial depth of about 200 m) was much less than 0.1 MPa. A single rock bolt support can keep the surrounding rock of the roadway stable; the compensation stress required for support in the medium buried coal roadway (with a depth of about 600 m) is around 0.1 MPa, and the combined support of rock bolts and cables can meet the support requirements. Deep coal roadways under high stress (with a depth of about 1000 m) require support to provide compensation stress. Even if the compensation stress reaches 0.2 MPa, the surrounding rock of the roadway will experience varying degrees of creep. In this study, it was necessary to increase the support density and surface area of rock bolts and cables, the pre-tension forces of rock bolts and cables were improved, and in synergy with grouting modification, destressing and other technologies could control the large deformation of the surrounding rock of the roadway in 1000 m deep coal mines. This study’s results provide a theoretical basis for the selection of control technologies for use in coal roadways at different depths.

1. Introduction

The excavation and unloading of coal mine roadways cause the stress readjustment of the surrounding rock, which, in turn, causes displacement of the roadway surrounding rock towards the excavation space. In order to prevent the destruction or even instability of the surrounding rock, it is necessary to implement active support for the surrounding rock of the roadway and restore its three-dimensional stress state, which provide support compensation stress that can achieve a new balance of internal stress in the surrounding rock [1,2,3].

As the depth of coal mining continues to increase, the in situ stress level becomes higher, and the difficulty of roadway support becomes greater. This is especially true in coal seam roadways due to the generally low strength, developed primary joint fissures, and the softness of the coal seams compared to other rock strata in coal seam strata (such as mudstone and sandy mudstone), which cause deep coal seam roadways to exhibit rapid deformation rate, large deformation amount, and even obvious rheological characteristics. Deep coal seam roadway support has become one of the major problems that coal mines urgently need to solve [4,5,6,7].

Stress is the fundamental driving force behind deformation and the failure of a roadway, and the change in the stress path directly determines the deformation time, magnitude, and failure mode. Therefore, it is necessary to study the stress evolution law of surrounding rock under roadway excavation and support conditions, as well as the deformation and failure law of coal seams under this path, which is greatly significant for determining the stress compensation scheme of roadway support.

In recent years, scholars, both domestically and internationally, have conducted extensive research into deep coal mine support and achieved significant results, greatly promoting the development of deep roadway support technology in China. In response to the current situation and existing problems of bolt support in coal mine roadways, the China Coal Research Institute Coal Mining Branch has conducted a series of refined studies of bolt support materials and components and developed a series of new materials and supporting components suitable for coal mine roadway support, which has significantly improved the support effect of coal mine roadways [8,9,10,11,12,13]. In recent years, the institution has also adopted various research methods to conduct in-depth research into the pre-stressed field of rock bolts and cables and basically understood the transmission law of the pre-stressed field of rock bolt support in the surrounding rock [14,15,16,17,18,19,20].

In terms of laboratory research into the process of rock failure, the current focus is mainly on the true triaxial tests, conventional triaxial tests, and acoustic emission tests of hard rock [21,22,23,24,25,26]. Research into simulating the stress path evolution process under rock excavation and support conditions is also limited to hard rock [27]. There are few reports on the stress path evolution process of coal under excavation and support conditions.

Based on the existing studies’ results, this paper takes the coal seam as the research object, using the true triaxial test method to simulate the deformation and failure process of the coal seam during the excavation and support of the coal roadway with different burial depths, discussing the reasonable support compensation stress required for the stability of the surrounding rock after the excavation of the coal roadway at different depths, and provides a reference for the design of the coal roadway bolt support, which enriches and improves the coal roadway bolt support theory.

2. Experiment Scheme Design

2.1. Experiment Equipment

This experiment was completed using the TRW-3000 micro-computer-controlled rock true triaxial electro-hydraulic servo testing system of Central South University, which is shown in Figure 1. The testing system adopted full-range servo control and can achieve independent loading in all three directions. It can perform loading and unloading tests on coal and rock samples through various combination paths. The maximum sample size tested via this testing system is 300 mm × 300 mm × 300 mm, and the maximum loads applied in the X, Y, and Z directions are 3000 kN, 2000 kN, and 2000 kN, respectively. It can be unloaded instantaneously on one side to simulate the excavation process. The extension meter was used to measure the deformation of X, Y, and Z in three directions, using a measuring range of ±3 mm. The acoustic emission monitoring system of PCI-II was adopted.

2.2. Coal Sample Collection and Processing

The experiment was conducted by taking coal samples from the coal mine site and processing them into cubes that met the test requirements. The sampling location was the 5-2 coal seam in the 50,103 working face of Hejiata Coal Mine in Yulin, Shaanxi. The thickness of coal seam was 3.1 m, and its uniaxial compressive strength was about 35 MPa. The sample acquisition process was defined as follows:

Firstly, the excavator was used to excavate the roadway in situ to obtain large irregular coal blocks;

Secondly, the coal blocks were wrapped in paraffin wax to reduce weathering;

Thirdly, the large cutter was used to cut large coal blocks into small cubes;

Finally, the surfaces of the samples were repeatedly polished using a small grinding machine.

Due to the development of joint fissures and disturbance in sampling and sample preparation within the coal seam, the success rate of coal samples with a size of 300 mm × 300 mm × 300 mm was extremely low, and the samples contained many large-scale cracks, which could not meet the test requirements. Therefore, the final coal sample were processed to a size of 150 mm × 150 mm × 150 mm. The comparison between two sizes of coal samples is shown in Figure 2. From the figure, it can be seen that there were multiple joint fissures on the surface of the coal sample, which was in line with the characteristics of the underground coal mass in the coal mine.

2.3. Test Programme

2.3.1. Determination of Confining Pressure

Previous studies’ results have shown that in areas with mild tectonic action, the average horizontal principal stress in coal rock strata is basically proportional to the elastic modulus of the coal rock mass. The larger the elastic modulus, the higher the horizontal stress [28,29,30,31,32]. Due to the fact that in situ stress measurement in coal mines is generally carried out in relatively complete and hard or shaly sandstone, the horizontal stress values present in coal seams could be estimated based on the elastic modulus ratio. The vertical stress could be estimated based on the depth of the roadway.

The measured in situ stress of Hejiata Coal Mine is shown in

Table 1. Measured rock in situ stress.

Depth/m	σv/MPa	σH/MPa	σh/MPa
189	4.73	11.86	6.2

, for which the vertical principal stress σ_V Press γH calculation was used. The in situ stress measurement was located in the sandstone strata of the roof, and the measured elastic modulus was 21 GPa. The elastic modulus of the coal mass was 3 GPa, which was equal to σ_Sandstone = 7 σ_Coal. The stress present in the coal seam after conversion is shown in

Table 2. Estimated stress in coal seams.

Depth/m	σv/MPa	σH/MPa	σh/MPa
200	5	1.7	1.0

.

This study’s results on the distribution law of in situ stress in coal mines indicated that the horizontal stress in mining areas with a depth of 250 m was significantly dominant, and the distribution characteristics of in situ stress were generally as follows: σ_H > σ_h > σ_V. The distribution characteristics of in situ stress in mining areas with depths of 250 m~600 m were generally σ_H > σ_V > σ_h, and the distribution characteristics of in situ stress in mines of more than 600 m in depth are generally σ_V > σ_H > σ_h [33].

Based on the estimated stress values in Table 2, without considering geological structural anomalies, the in situ stresses of coal seams buried at depths of 600 m and 1000 m are assumed, as shown in

Table 3. In situ stress in coal seams.

Depth/m	σv/MPa	σH/MPa	σh/MPa
600	15	2.6	1.7
1000	25	3.4	2.4

.

2.3.2. Determination of Support Stress

According to the results of the similar simulation studies in references [19,34], for the cables with 1 m × 1 m row and line spacing and 300 kN pre-tension force, the supporting pre-stress field can form a uniform and continuous compressive stress zone of around 0.15 MPa from the surface of the model to the depth of 1 m; the rock bolts with 1 m × 1 m row and line spacing and 100 kN pre-tension force can form a uniform and continuous compressive stress zone of around 0.05 MPa. If combined support with rock bolts and cables was used, a continuous and uniform compressive stress zone within 0.2 MPa could be formed near the surface of the surrounding rock.

Based on the above conclusion, the recovery value of confining pressure in this experiment is limited to less than 0.2 MPa.

2.3.3. Stress Path Design

Figure 3 shows the schematic diagram of stress states at different stages of the roadway. The reasonable support compensation stress is determined via the test of true triaxial loading + unidirectional unloading + compensation stress on the sample. The time of stress compensation is near the failure state after the unidirectional unloading of the coal sample. The initial loading of the test is determined according to Table 2 and Table 3 for the three-dimensional in situ stress values of the coal seam. Based on the time sequence of roadway excavation and support, as well as the numerical simulation results of the evolution law of the main stress of the surrounding rock during roadway excavation, the path for the true triaxial loading + unidirectional unloading + compensation stress test was determined as follows: Firstly, the stress values shown in Table 2 and Table 3 were loaded in three directions to simulate the in situ stress. Then, the minimum principal stress was unloaded to 0, the middle principal stress remained unchanged after unloading, and the maximum principal stress remained stable after increasing by a certain value, simulating the process of coal roadway excavation. When the coal sample was about to be damaged, stress compensation should be immediately carried out in the minimum stress direction to restore the sample from two-dimensional to three-dimensional stress. The specific steps used were as follows:

(1)

Synchronize loading of X, Y, and Z triaxial stresses to σ₃;

(2)

Keep σ₃ constant and synchronously load the stress in the other two directions to σ₂;

(3)

Keep σ₂ and σ₃ constant and load the Z direction stress to σ₁;

(4)

Lock the oil cylinder and hold it until the sample is stable and keep σ₃, σ₂ unchanged, quickly adjusting σ₃ unloading to 0;

(5)

Reduce σ₂ by 10% to maintain stability, and load σ₁ to the coal sample near the failure state;

(6)

Quickly compensate σ₃ to 0.2 MPa to observe whether the deformation of the coal sample tends to be stable;

(7)

If the deformation of the coal sample is stable, unload σ₃ to 0.1 MPa and continue to observe whether the deformation of the coal sample remains stable;

(8)

If the deformation is still stable, further unload σ₃ to 0, and if it is stable, repeat steps 5, 6, 7, and 8 until the coal sample is broken.

Figure 3. Schematic diagram of stress states at different stages of the roadway: (a) before excavation—triaxial stress state; (b) excavation unloading—bi-directional stress state; (c) support compensation—restoring the three-dimensional stress state.

Figure 3. Schematic diagram of stress states at different stages of the roadway: (a) before excavation—triaxial stress state; (b) excavation unloading—bi-directional stress state; (c) support compensation—restoring the three-dimensional stress state.

3. Test Results and Analysis

3.1. Reasonable Support and Compensation Stress for 200 m Buried Deep Coal Roadway

The reasonable support compensation stress is the critical compensation stress value required to make the coal sample deformation stable.

(1)

Deformation law

Figure 4 shows the maximum principal strain and minimum principal stress–time curves. The minimum principal stress direction is unloading and moving in the compensation stress direction. Combining the two curves for analysis, the effect of compensation stress is explained through the change in the strain during stress compensation, and a reasonable compensation stress value is determined.

• ①

  During the three directions’ loading process, the strain of the coal sample increases continuously in the direction of the minimum principal stress due to the continued loading in the other two directions. The confining pressure unloading operation can be carried out until the end of the whole three-way loading process, and the slope of the strain curve is basically 0.

  ②

  After the minimum principal stress is unloaded to 0 MPa, the slope of the strain curve remains basically 0 within 1 min. After 1 min, the strain begins to increase, but the slope of the strain curve is significantly lower than that of the curve under the three directions of loading before the failure.

  ③

  When the compensation stress is applied to 0.2 MPa immediately before the coal sample is near to failure, the strain curve quickly changes from vertical to horizontal, and the deformation of the coal sample changes from rapid growth to stability, indicating that the application of 0.2 MPa compensation stress can keep the coal sample stable.

  ④

  When the compensated stress is reduced to 0.1 MPa, the coal sample deforms immediately when the compensated stress is reduced, and the strain of the coal sample basically remains unchanged when the compensated stress is maintained at 0.1 MPa, indicating that the compensated stress at 0.1 MPa can also keep the coal sample stable.

  ⑤

  When the compensated stress is reduced to 0, the deformation of the coal sample increases rapidly in the process of reducing the compensated stress, and then the deformation speed slows down. After 3 min, the deformation speed increases rapidly until the coal sample is destroyed, indicating that the stability of the coal sample cannot be guaranteed under the condition of no compensated stress.

(2)

Acoustic emission characteristics

Figure 5 shows the time curve of the minimum principal stress and acoustic emission count. By analyzing the acoustic emission characteristics of the coal sample in the process of stress compensation, the stability of the coal sample is judged, and then the reasonable compensation stress value is determined.

• ①

  Less than 9 min after unidirectional confining pressure unloading, the acoustic emission count is less, and the coal sample is in a relatively stable period. After this point, the acoustic emission counts increase sharply, and the coal sample is in a critical failure and instability state. At this time, the stress is quickly compensated to 0.2 MPa, and the acoustic emission counts are rapidly reduced from active to calm. The results show that the compensation stress of 0.2 MPa can keep the coal sample stable and effectively restrain the propagation of internal cracks.

  ②

  When the compensated stress is reduced from 0.2 MPa to 0.1 MPa, the acoustic emission counts do not increase significantly, indicating that the compensated stress of 0.1 MPa can also keep the coal sample stable.

  ③

  When the compensated stress is reduced to 0 MPa, the acoustic emission counts increase sharply and become more and more involved in the process of pressure relief. After about 3 min, the coal sample becomes unstable and failure occurs, indicating that the coal sample without compensated stress cannot guarantee long-term stability.

(3)

Sound characteristics

①

When the coal sample is near instability and failure, the severe sound of coal mass failure can be heard, the stress is quickly compensated to 0.2 MPa, and the sound of coal sample rupture disappears. Within 5 min, only a small sound occasionally appears, indicating that 0.2 MPa stress compensation can keep the coal sample stable.

②

When the compensation stress is reduced to 0.1 MPa, the coal sample has a certain sound, and there is almost no sound within 5 min of the pressure holding, indicating that the compensation stress of 0.1 MPa can also keep the coal sample stable.

③

When the compensated stress is reduced to 0, there is a small amount of sound in the coal sample, and then there is a non-violent sound. About 3 min later, the coal sample suddenly makes a dramatic sound and becomes unstable, indicating that the coal sample without compensated stress cannot maintain stability.

④

To sum up, the reasonable support compensation stress of the coal roadway buried at a 200 m depth is much lower than 0.1 MPa.

3.2. Reasonable Support and Compensation for Stress in a 600 m Deep Coal Roadway

(1)

Deformation law

Figure 6 shows the maximum principal strain and minimum principal stress–time curves.

• ①

  After three-dimensional loading, the minimum principal stress is unloaded to 0 MPa, and during the unloading process, the strain increases sharply in a short period of time, with the strain curve basically showing a vertical shape. Afterwards, the rate of the strain curve decreased and remained basically constant, but the slope of the strain curve was significantly greater than that during the three-dimensional loading period before failure.

  ②

  After unidirectional unloading of confining pressure, stress compensation is immediately changed to 0.2 MPa when the coal sample is approaching instability and failure. The strain curve quickly changes from vertical to nearly horizontal, indicating that the deformation of the coal sample increases sharply and decreases rapidly due to the effect of compensating stress. The strain remains unchanged during the pressure-maintaining process, indicating that 0.2 MPa compensating stress can maintain the stability of the coal sample.

  ③

  During the process of reducing the compensation stress to 0.1 MPa, although the strain increased in the short term, it remained almost unchanged thereafter, indicating that a compensation stress of 0.1 MPa can also maintain the stability of the coal sample.

  ④

  During the process of reducing the compensation stress to 0, the maximum principal strain of the coal sample increases sharply, and the coal sample rapidly becomes unstable and fails.

(2)

Acoustic emission characteristics

Figure 7 shows the minimum principal stress and acoustic emission counts–time curves.

• ①

  During the process of the three-dimensional loading of coal samples, a small amount of acoustic emission behavior occurs, and during the stable period of three-dimensional loading, there is very little acoustic emission behavior. After the unidirectional unloading of the confining pressure, the acoustic emission behavior gradually increases until it approaches an unstable state. When the coal sample is near failure and the stress is immediately compensated to 0.2 MPa, the acoustic emission counts gradually decrease. When the compensated stress is maintained at 0.2 MPa, the acoustic emission behavior occurs only occasionally and is basically in a calm period, indicating that the compensated stress of 0.2 MPa can effectively inhibit internal crack generation and the expansion of the coal sample, and the coal sample can maintain stability.

  ②

  When the compensated stress is reduced to 0.1 MPa, only a small amount of acoustic emission behavior appears, indicating that the acoustic emission activity is still in a calm period, indicating that 0.1 MPa of compensated stress can also effectively inhibit internal crack fracture and the expansion of the coal sample, no continuous deterioration occurs, and the coal sample can still remain stable.

  ③

  When the compensation stress is reduced to 0, the acoustic emission counts suddenly increased sharply, and the coal sample quickly became unstable and damaged.

(3)

Sound characteristics

①

After the unidirectional unloading of coal samples, the frequency and sound of cracks increase gradually. When the coal sample is near to failure, the stress is compensated to 0.2 MPa immediately, and the sound gradually disappears. Within 5 min of maintaining the 0.2 MPa compensation stress, only occasional slight sound appears, indicating that the 0.2 MPa compensation stress can restrain the further damage of the coal sample and maintain stability.

②

When the compensated stress is reduced to 0.1 MPa and the pressure is stabilized for 5 min, the coal sample continues to have a slight sound, indicating that the compensated stress of 0.1 MPa can basically keep the coal sample stable, and the internal part does not crack in a wide range, but micro-cracks still occur.

③

In the process of reducing the compensation stress to 0, the coal sample has a violent sound and rapidly loses stability.

In summary, the reasonable support compensation stress required for a 600 m deep coal roadway is around 0.1 MPa.

3.3. Reasonable Support and Stress Compensation for 1000 m Buried Coal Roadway

(1)

Deformation law

Figure 8 shows the maximum principal strain and minimum principal stress–time curves.

• ①

  After the three-dimensional loading is completed and the maximum principal strain remains stable, the minimum principal stress is unloaded to 0 MPa, the maximum principal strain increases rapidly, and the slope of the strain curve is significantly greater than the slope during the three-dimensional loading period before the failure.

  ②

  In the process of compensating stress to 0.2 MPa and holding for 5 min, the slope of maximum principal strain–time curve decreases by about 50%, and the strain of coal sample continues to grow slowly, but there is no damage in the short term, indicating that although the compensated stress of 0.2 MPa can keep the coal sample relatively stable, an obvious creep phenomenon has occurred.

  ③

  When the compensated stress is reduced to 0.1 MPa, the slope of the strain curve of the coal sample increases sharply and then decreases, but the slope of the strain curve is still larger than that of the 0.2 MPa stress compensation, indicating that the creep rate of the coal sample is further increased, and the coal sample becomes unstable after about 8 min. The results show that the compensation stress of 0.1 MPa can only slow down crack generation and the expansion rate of coal sample, but it cannot maintain stability.

(2)

Acoustic emission characteristics

Figure 9 shows the minimum principal stress and acoustic emission count–time curves.

• ①

  During the three-dimensional loading period, both the acoustic emission counts and the energy are low. After unidirectional unloading, the acoustic emission counts gradually increase, and the energy increases until the adjacent coal sample is destroyed.

  ②

  When the stress is immediately compensated to 0.2 MPa when the coal sample is near to failure, the acoustic emission counts and energy are significantly reduced, and the activity is also reduced, but there are still small energy acoustic emission events that occur constantly, indicating that there are still small cracks in the coal sample under the 0.2 MPa compensated stress, and the coal sample can basically maintain stability in a certain period of time.

  ③

  When the compensated stress is reduced to 0.1 MPa, the acoustic emission counts increase sharply in the process of compensation stress reduction, and then the small energy acoustic emission events continuously continue. At the 8th minute, the large energy acoustic emission is frequent, and the coal sample is unstable and destroyed.

(3)

Sound characteristics

①

After the unidirectional unloading of the coal sample, intermittent sound is heard, and with the passage of time, the frequency of sound gradually increases, and the sound becomes louder and louder until the coal sample is near destruction.

②

When the coal sample is near instability, the stress is immediately compensated to 0.2 MPa, and the sound is immediately slowed down. Within the time of maintaining the 0.2 MPa compensated stress, only a slight sound occurs, indicating that the deformation of the coal sample is relatively stable, and micro-cracks only occasionally open.

③

In the process of reducing the compensation stress to 0.1 MPa, the coal sample continued to crack, and the sound slowed down in the process of maintaining pressure. At the 8 min mark, the sound of the coal sample was extremely strong, and the coal sample was unstable and damaged.

In summary, the reasonable support compensation stress for a 1000 m deep coal roadway is more than 0.2 MPa.

4. Discussion

Subject to the field conditions, it is very difficult to obtain large-sized samples, but the size has a great impact on the test results, mainly in relation to two aspects: firstly, the small-sized samples contain fewer cracks, and secondly, size has an influence on the strength and other parameters of the samples. The conclusion can provide some guidance for the determination of support stress in different buried roadways, but the specific scheme should consider these factors to improve the support strength and ensure the support effect. In future research, the sample test of 300 mm × 300 mm × 300 mm or larger will be carried out based on the numerical simulation method.

Only the increase in the in situ stress was considered for different depths, and the change in geological conditions and the impact of mining on the environment were not considered. Before creating the support scheme, the geological conditions should be evaluated first, and the differentiated design should be made closer to the actual working conditions. A reasonable support scheme can effectively control the large deformation of the roadway, the collapse of roadway roof was controlled, and then we reduced the damage to subsidence, water table effects, and habitat disruption.

The test results provide guidance for the determination of support stress, but the specific scheme needs to be formulated according to the geological conditions, such as rock type, faulting, and bedding planes. In addition, only bolt and cable were simply proposed, while other support technologies and components were not considered. For the shallow roadway at 200 m, only bolt support was used; for the buried depth of 600 m, bolt, cable, and mesh support were required; and for the buried depth of 1000 m, bolt, cable, mesh, shotcrete, and grouting were required. The above suggestions have been successfully applied in northern Shaanxi, Shanxi, and Huainan mining areas, and they are basically consistent with field applications.

The research included in this article focuses on coal seam roadways that are only affected by the excavation of this roadway. In the case of roadways being affected by other excavation or mining, the required support compensation stress will significantly increase, even if it is difficult to meet safety and production requirements. In this case, in synergy with the bolting–modification–destressing method can be considered. Taking Kouzidong Mine in the Huainan Mine area of China as an example, control technology by means of bolting–modification–destressing in synergy was adopted. Its principle was as follows: advance grouting was carried out before excavation to improve the strength and integrity of the soft coal mass, providing a good bolting foundation, and then high-prestressed bolt and cable was used. The dilatation deformation was controlled in the early stage, and the hard rock above the roadway was cut to relieve pressure before mining, the mining stress of high magnitude value was greatly reduced, and collaborative control was realized. Practice has proved that the roadway deformation was reduced by more than 50%.

5. Conclusions

(1) The excavation of coal mine roadways causes the stress of the surrounding rock to readjust, and the surrounding rock gradually shifts towards the excavation space. To prevent the deformation, damage, or even instability of the surrounding rock, it is necessary to implement timely active support for the surrounding rock of the roadway, restore its three-dimensional stress state, and provide support to compensate for stress, so that the surrounding rock can reach a new balance.

(2) Due to the different levels of stress present in the surrounding rock, there is a significant difference in the required support compensation stress for roadways with different burial depths. This study’s results indicate that the compensation stress required for support in shallow buried roadways (200 m or shallower) is much less than 0.1 MPa. Simply using rock bolt support can maintain the stability of the surrounding rock.

(3) The compensation stress required for support in a medium buried coal roadway (with a depth of about 600 m) is around 0.1 MPa, and the combined support of rock bolts and cables can meet the support requirements.

(4) Even if the compensating stress provided by the support in deep coal roadways under high stress (buried at the depth of about 1000 m) reaches 0.2 MPa, the surrounding rock of the roadway will experience varying degrees of creep. It is necessary to increase the support density and surface area of rock bolts and cables, the pre-tension force of rock bolts and cables can improve, and, in synergy with grouting modification, destressing and other technologies can be used to control the large deformation of the surrounding rock of the roadway in 1000 m deep coal mines.