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21 pages, 4777 KiB

Open AccessArticle

Simulating the Hydraulic and Volume Change Behavior of Compacted Highly Expansive Soil under Potential Field Stress and Seasonal Climatic Variation

by Mohamed Farid Abbas

Sustainability 2023, 15(14), 10797; https://doi.org/10.3390/su151410797 - 10 Jul 2023

Viewed by 731

Abstract

A sustainable design of some engineering applications, such as earth dam cores, landfill liners, clay barriers, and radioactive waste disposal systems, that utilize compacted expansive soils requires simulation for probable field conditions. This study investigated the hydraulic and volume change (H-VC) behaviors of [...] Read more.

A sustainable design of some engineering applications, such as earth dam cores, landfill liners, clay barriers, and radioactive waste disposal systems, that utilize compacted expansive soils requires simulation for probable field conditions. This study investigated the hydraulic and volume change (H-VC) behaviors of highly expansive compacted soils in Al-Qatif city under different seasonal climatic variations for a wide range of stress conditions, aiming for more economical and rational design and practices. The extent of the effect of the start cycle condition of the cyclic wetting and drying (W/D) process on the examined properties is examined, as well. Two testing series of the cyclic W/D process, representing the probable seasonal climatic variations, were executed for varied axial stress conditions. The H-VC behaviors of expansive soils are affected by the simulated seasonal variation (i.e., cyclic W/D process), with the first cycle of W/D being the most effective cycle and an elastic state being attained by the third to fourth cycle. Swell fatigue is noted for both testing series, and this is attributed to the initial placement condition. Analysis of results recommends exposure of the compacted expansive soil layers in the field to drying after compaction to reduce their equilibrium wetting potential. As a consequence of the noted shrinkage accumulation, a reduction tendency of saturated hydraulic conductivity (k_sat) with repeated W/D cycles is reported for both series under all the stress states applied. Finally, it is recommended for clay barrier projects to be submerged once compacted to obtain barriers with the lowest values of hydraulic conductivity. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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15 pages, 3857 KiB

Open AccessArticle

Aeolian Sand Test with True Triaxial Stress Path Achieved by Pseudo-Triaxial Apparatus

by Zhigang Ma and Xuefeng Li

Sustainability 2023, 15(10), 8328; https://doi.org/10.3390/su15108328 - 19 May 2023

Cited by 3 | Viewed by 1016

Abstract

Aeolian sand is a special roadbed filler, but its three-dimensional mechanical properties are rarely studied. To obtain the characteristic of its deformation, strength on the deviatoric plane, and failure in three dimensions, a series of triaxial drained tests on aeolian sand in the [...] Read more.

Aeolian sand is a special roadbed filler, but its three-dimensional mechanical properties are rarely studied. To obtain the characteristic of its deformation, strength on the deviatoric plane, and failure in three dimensions, a series of triaxial drained tests on aeolian sand in the Tengger Desert, under the condition of the constant average principal stress, p, were conducted by an equivalent alternative method to achieve a true triaxial stress path by a pseudo-triaxial apparatus. The results show that the method can better determine the strength. The peak shear stress decreases gradually with the increase of the intermediate principal stress coefficient, b, at the same p. Compared with the SMP and Mohr–Coulomb criteria, the peak shear stress is near the strength lines predicted by both criteria. At a lower p, the specimen exhibited strain-softening behaviours, but at a higher p, it showed hardening behaviours. Under the conditions of a higher p and lower b, the specimen exhibited contraction first and then dilatancy. The specimen deformation is greatly affected by anisotropy, and as the p-value increases, the effect of the initial anisotropy on the specimen begins to weaken. The ε_s (generalized shear strain)/η (stress ratio)-ε_s curves, can be expressed by a linear equation, of which the slope is affected by the b-value. The experiment verifies the feasibility and rationality of the equivalent method. The test data provide support for the maintenance of desert roadbeds and the sustainable development of the economy and society in ecologically fragile areas. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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21 pages, 7207 KiB

Open AccessArticle

Tunnel Face Stability Considering the Influence of Excess Slurry Pressure

by Junhao Zhong, Shihe Zhao, Pengqin Wang and Chuantan Hou

Sustainability 2023, 15(10), 8230; https://doi.org/10.3390/su15108230 - 18 May 2023

Cited by 2 | Viewed by 1045

Abstract

With excess slurry pressures exerted on the tunnel face, slurry particles tend to infiltrate into the soil in front of the tunnel. There will be excess pore pressure ahead of the tunnel in the case of infiltration, leading to an impairment in the [...] Read more.

With excess slurry pressures exerted on the tunnel face, slurry particles tend to infiltrate into the soil in front of the tunnel. There will be excess pore pressure ahead of the tunnel in the case of infiltration, leading to an impairment in the supporting effect contributed by the excess slurry pressure. Corresponding to three slurry infiltration scenarios distinguished by the forms of the filter cake, different pressure transfer models are employed to describe the pore pressure distribution. Using the kinematic approach of limit analysis and the numerically simulated seepage field, the study of tunnel face stability under different slurry infiltration cases is extended by employing a 3D discretization-based failure mechanism. In addition, two simple empirical formulas describing the pore pressure distributions above the tunnel and in advance of the tunnel are established and verified. Combined with the dichotomy method and strength reduction method, the safety factors yielding rigorous upper-bound solutions are obtained by optimization. The proposed method is validated by a comparative analysis. The developed framework allows considering the influence of excess pore pressure on the whole failure mechanism and the three-dimensional characteristics of seepage. A parameter analysis is performed to study the effect of the excess slurry pressure, hydraulic conditions, soil strength properties, and pressure drop coefficient. The results show that the steady-state flow model leads to much more conservative results than the full-membrane model. The safety factor increases with the increasing excess slurry pressure and the decreasing pressure drop coefficient. The present work provides an effective framework to quickly assess the face stability of tunnels under excess slurry pressure considering different filter cake scenarios. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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25 pages, 16775 KiB

Open AccessArticle

Field Investigation and Finite Element Analysis of Landslide-Triggering Factors of a Cut Slope Composed of Granite Residual Soil: A Case Study of Chongtou Town, Lishui City, China

by Tiesheng Yan, Jun Xiong, Longjian Ye, Jiajun Gao and Hui Xu

Sustainability 2023, 15(8), 6999; https://doi.org/10.3390/su15086999 - 21 Apr 2023

Cited by 3 | Viewed by 1423

Abstract

Landslides caused by excavations and precipitation events are widespread types of slope failures in southwest Zhejiang, China, in areas with granite residual soil. Investigations of the effect of high precipitation on the hydrological response, stability, and evolutionary mechanism of cut slopes in granite [...] Read more.

Landslides caused by excavations and precipitation events are widespread types of slope failures in southwest Zhejiang, China, in areas with granite residual soil. Investigations of the effect of high precipitation on the hydrological response, stability, and evolutionary mechanism of cut slopes in granite soil areas are lacking. The characteristics of historical landslides in Chongtou Town in southwestern Zhejiang were summarized, and a typical slope was selected for analysis. The hydraulic and mechanical properties of the residual soil and fully weathered granite were tested, and the surface displacements on the slope were monitored. Geo-studio was utilized to establish a coupled seepage-deformation model to validate the numerical method and investigate the landslide-triggering factors of the cut slope. The results showed nearly all historical landslides in Chongtou Town were triggered by precipitation events, and the slide bodies consisted of residual soil and fully weathered granite with similar geotechnical properties. The simulated and measured horizontal displacements were in good agreement, indicating the reliability of the established model and parameters. The stability coefficient decreased with an increase in the gradient or height of the cut slope. The critical height values were 5.3 m, 5.5 m, 5.7 m, 6.0 m, and 6.3 m at slopes of 60°, 65°, 70°, 75°, and 80°, respectively. Long-term torrential rain and short-term high-intensity precipitation events are likely to trigger landslides when the precipitation event lasts longer than 26 h and 78 h, respectively. The landslide formation includes four stages: slope evolution, formation of unloading zone at slope foot, migration and loss of soil particles, and instability of the cut slope. The findings can be used to prevent and manage landslides on cut slopes in areas with granite residual soil. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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22 pages, 6950 KiB

Open AccessArticle

Consolidation by Vertical Drains Considering the Rheological Characteristics of Soil under Depth and Time-Dependent Loading

by Siliang Shen and Zheyu Hu

Sustainability 2023, 15(7), 6129; https://doi.org/10.3390/su15076129 - 03 Apr 2023

Viewed by 1151

Abstract

Vertical drains have been widely used in soil improvement projects to accelerate consolidation and improve the strength of soft soil. Previous consolidation models are mainly based on instantaneous loading, which cannot reflect the actual time-variable loading condition. This paper presents a set of [...] Read more.

Vertical drains have been widely used in soil improvement projects to accelerate consolidation and improve the strength of soft soil. Previous consolidation models are mainly based on instantaneous loading, which cannot reflect the actual time-variable loading condition. This paper presents a set of analytical solutions for consolidation with vertical drains under depth and time-dependent loading, involving one-step loading, multi-step loading, and cyclic loading. A four-element model, which is a combination of the Merchant model and Maxwell model, is introduced to consider the rheological characteristics of the soil. By simulating the results of a consolidation test, it is found that the four-element model is more accurate than the Merchant model in predicting the changes in pore pressure and settlement during the clay consolidation process. Based on the solutions obtained, several factors affecting consolidation behavior are investigated. It has been shown that the rheological behavior becomes more and more obvious at the later stage of consolidation with the decrease both in the modulus of the spring in the Kelvin body and the viscosity coefficient of the independent dashpot. With the increase in the viscosity coefficient of the dashpot in the Kelvin body, the rate of consolidation becomes faster at an initial stage but slower at a later stage. For cyclic loading, the consolidation degree in each cycle reaches a maximum at the end of unloading and reaches a minimum at the beginning of the loading. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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16 pages, 4418 KiB

Open AccessArticle

Factors Affecting the Maximum Leachate Head in the Landfill Drainage Layer under Clogging Conditions

by Siliang Shen and Zheyu Hu

Sustainability 2023, 15(6), 5049; https://doi.org/10.3390/su15065049 - 13 Mar 2023

Cited by 1 | Viewed by 1182

Abstract

Clogging of the landfill drainage layer leads to a high leachate head developing over the bottom liner, which increases the risk of leachate leakage. Estimation of the maximum leachate head in the landfill drainage layer is of great significance to the pollution control [...] Read more.

Clogging of the landfill drainage layer leads to a high leachate head developing over the bottom liner, which increases the risk of leachate leakage. Estimation of the maximum leachate head in the landfill drainage layer is of great significance to the pollution control of bottom liners. In this study, a simplified model considering the development of clogging is established through assuming the spatial and temporal distributions of clogging in a drainage layer of landfill. The calculation results are compared with a previous study to verify the proposed model. Through parameter analysis, it is discovered that the larger the initial hydraulic conductivity, the less the influence of clogging on the leachate head at the beginning, but it will increase over time. Meanwhile, a longer drainage distance, a larger inflow rate, or a higher ion concentration will lead to a greater influence of clogging on the leachate head. The completion time of clogging is more sensitive to the variation of inflow rate and ion concentration. In order to effectively control the maximum leachate head, it is suggested that the drainage material with large hydraulic conductivity such as pebbles or gravel should be used, the drainage slope should be greater than 4%, the drainage distance should be controlled at 20 m, and calcium products should be removed from leachate through adsorption, precipitation, or waste reuse. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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14 pages, 3495 KiB

Open AccessArticle

Study on the Influence Mechanism of Sample Preparation Method on the Shear Strength of Silty Soil

by Xinyan Ma, Qian Yu, Mingmin Xuan, Huaping Ren, Xinyu Ye and Bo Liu

Sustainability 2023, 15(3), 2635; https://doi.org/10.3390/su15032635 - 01 Feb 2023

Cited by 1 | Viewed by 1133

Abstract

During the compaction of silty soil subgrade, different filling methods are adopted, which will significantly impact the subgrade performance, but few studies have been applied to quantify this influence. To explore the influence mechanism of dry density and sample preparation method (compaction and [...] Read more.

During the compaction of silty soil subgrade, different filling methods are adopted, which will significantly impact the subgrade performance, but few studies have been applied to quantify this influence. To explore the influence mechanism of dry density and sample preparation method (compaction and static compression method) on the shear strength of silty soil, the consolidated undrained shear test (CU test), dynamic triaxial test, and nuclear magnetic resonance microscopic test on silty soil were carried out in this study. The test results show that the shear strength of the sample is positively correlated with the dry density. The influence of the sample preparation method on shear strength is mainly reflected in the cohesion. The pore size distributions obtained by different sample preparation methods had smaller differences before the CU test. However, significant differences were observed after the CU test, indicating that the influence of the sample preparation method on the shear strength of the sample is not on the initial pore distribution but on the residual stress and overall uniformity. The dynamic triaxial tests show that a differential settlement may occur when multiple sample preparation (soil-filling method in subgrade practice) methods are adopted. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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18 pages, 6950 KiB

Open AccessArticle

Land Subsidence Characteristics and Numerical Analysis of the Impact on Major Infrastructure in Ningbo, China

by Feng Gao, Tuanzhi Zhao, Xuebin Zhu, Lingwei Zheng, Wenjun Wang and Xudong Zheng

Sustainability 2023, 15(1), 543; https://doi.org/10.3390/su15010543 - 28 Dec 2022

Cited by 2 | Viewed by 1797

Abstract

For the construction and safe operation of major infrastructure in coastal cities, the impact of regional land subsidence that has occurred or is slowly proceeding deserves attention. Previous studies have mainly focused on the surrounding land subsidence caused during construction or operation, as [...] Read more.

For the construction and safe operation of major infrastructure in coastal cities, the impact of regional land subsidence that has occurred or is slowly proceeding deserves attention. Previous studies have mainly focused on the surrounding land subsidence caused during construction or operation, as well as the superposition effect of land subsidence caused by groundwater extraction. However, research on the different impacts of damage due to land subsidence in the construction and operation of urban infrastructure needs to be carried out according to the actual geological environmental conditions, reflected in parameters such as the soil properties and common loads. Numerical simulation cannot fully reflect the details of reality; however, it can avoid the influence of other conditions to focus on different factors influencing land subsidence and thus highlight the contribution of a single factor influencing land subsidence. Therefore, in this paper, we adopt field measurement data and carry out a numerical simulation analysis of different influencing factors. First, taking the Ningbo Jiangdong subsidence center (now located in Yinzhou District) as an example, area growth, cumulative subsidence and the occurrence and development of the subsidence rate of a typical urban subsidence funnel area are analyzed. Then, taking the Ningbo Chunxiao–Meishan area as an example, based on the physical and mechanical characteristics of the main soil layers in the coastal reclamation area, a numerical analysis of the self-weight/backfill and surcharge consolidation settlement of the soil layer (considering the water permeability/impermeability of the bottom surface) and a numerical analysis of the nonuniform settlement caused by pile foundation engineering are carried out. Finally, the Ximenkou–Gulou area is taken as the analysis object. Numerical simulation of metro tunnel pipeline deformation is carried out considering uniform/nonuniform settlement. The results show that the comprehensive prohibition of groundwater exploitation is beneficial to slow the land subsidence rate, while the sedimentation of silty clay in Layer 4 (muddy clay) is the largest among all the soil layers. Compared with uniform settlement, nonuniform settlement is more likely to cause connection failure between tunnel segments. The above research results can provide references for the prevention and control of land subsidence and thus the safe operation of major infrastructure. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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21 pages, 8947 KiB

Open AccessArticle

Dynamic Response Analysis on Stress and Displacement of the Shield Tunnel Structure and Soil Layer under Train-Induced Vibration in Xiamen Metro Line 6

by Jiaqi Guo, Lexin Xu, Chong Xu, Ruimin Chen and Jinhai Lin

Sustainability 2022, 14(19), 11962; https://doi.org/10.3390/su141911962 - 22 Sep 2022

Cited by 7 | Viewed by 1678

Abstract

Tunnel engineering develops rapidly. To study the dynamic response of shield tunnel structure and its bottom soil layer caused by metro train operation, a three-dimensional finite-difference dynamic calculation method is used to establish a shield tunnel-soil layer coupling model based on the shield [...] Read more.

Tunnel engineering develops rapidly. To study the dynamic response of shield tunnel structure and its bottom soil layer caused by metro train operation, a three-dimensional finite-difference dynamic calculation method is used to establish a shield tunnel-soil layer coupling model based on the shield tunnel project of Maluan Central Station-Jimei Island Station of Xiamen Metro Line 6, and the dynamic response of tunnel structure and its bottom soil layer caused by metro train operation is calculated. The results show that: Under the action of train-induced vibration, the shield tunnel structure mainly bears compressive stress and generates compressive deformation. The dynamic response of tunnel structure represents a significant increasing trend with the enhancement of train-induced vibration load. Under the same load strength, dynamic response change amplitude of structure is not obvious with tunnel structural stiffness, stress is gradually increasing, and displacement is weakening. The deeper the soil depth at the bottom of the shield tunnel structure, the weaker the dynamic response of the soil layer. The stress response of the soil layer at the same depth is increasing with the train-induced vibration load improving, but the displacement response has a stage characteristic. The dynamic response of the soil layer at the same depth does not change obviously with the increase in shield tunnel structural stiffness, but the stress response gradually increases, and the displacement response becomes weak. In general, investigation of the dynamic response of the subway shield tunnel under train-induced vibration has important practical significance for maintaining the long-term safe operation of subway tunnels. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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16 pages, 5193 KiB

Open AccessArticle

Study on Stability of Anchored Slope under Static Load with Weak Interlayer

by Mengliang Gao, Haifeng Gao, Qiang Zhao, Zhihuan Chang and Chenxi Miao

Sustainability 2022, 14(17), 10542; https://doi.org/10.3390/su141710542 - 24 Aug 2022

Cited by 2 | Viewed by 1206

Abstract

To study the stability characteristics of a rock slope with a weak interlayer, a test of the anchor frame slope was designed in this paper. The analysis model was established with FLAC^3D, and the development law of safety factor, deformation, axial [...] Read more.

To study the stability characteristics of a rock slope with a weak interlayer, a test of the anchor frame slope was designed in this paper. The analysis model was established with FLAC^3D, and the development law of safety factor, deformation, axial anchor force, soil pressure and maximum shear strain increment of the slope, and the supporting effect of frame anchor cable were obtained by grading loading. The research showed that the supporting effect of frame anchor cable support on the slope was remarkable, and the influence of slope vertical load on the slope safety factor was evident. The lateral deformation mode of the slope surface was large up and down, and minor in the middle. The weak intercalated layer blocked the internal diffusion of the settlement. The failure trend of slope was sliding along the weak interlayer and collapse occurred below the loading zone, and the final failure mode is wedge failure. The peak value of maximum shear strain increment was developed along the weak interlayer, and a shear strain mutation zone was formed inside the slope. It could be considered that the weak interlayer was the potential sliding surface of the slope. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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17 pages, 4157 KiB

Open AccessArticle

Predictions of Geological Interface Using Relevant Vector Machine with Borehole Data

by Xiaojia Ji, Xuanyi Lu, Chunhong Guo, Weiwei Pei and Hui Xu

Sustainability 2022, 14(16), 10122; https://doi.org/10.3390/su141610122 - 15 Aug 2022

Viewed by 1062

Abstract

Due to the discreteness, sparsity, multidimensionality, and incompleteness of geotechnical investigation data, traditional methods cannot reasonably predict complex stratigraphic profiles, thus hindering the three-dimensional (3D) reconstruction of geological formation that is vital to the visualization and digitization of geotechnical engineering. The machine learning [...] Read more.

Due to the discreteness, sparsity, multidimensionality, and incompleteness of geotechnical investigation data, traditional methods cannot reasonably predict complex stratigraphic profiles, thus hindering the three-dimensional (3D) reconstruction of geological formation that is vital to the visualization and digitization of geotechnical engineering. The machine learning method of relevant vector machine (RVM) is employed in this work to predict the 3D stratigraphic profile based on limited geotechnical borehole data. The hyper-parameters of kernel functions are determined by maximizing the marginal likelihood using the particle swarm optimization algorithm. Three kinds of kernel functions are employed to investigate the prediction performance of the proposed method in both 2D analysis and 3D analysis. The 2D analysis shows that the Gauss kernel function is more suitable to deal with nonlinear problems but is more sensitive to the number of training data and it is better to use spline kernel functions for RVM model trainings when there are few geotechnical investigation data. In the 3D analysis, it is found that the prediction result of the spline kernel function is the best and the relevant vector machine model with a spline kernel function performs better in the area with a fast change in geological formation. In general, the RVM model can be used to achieve the purpose of 3D stratigraphic reconstruction. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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25 pages, 3819 KiB

Open AccessArticle

Inclined Layer Method-Based Theoretical Calculation of Active Earth Pressure of a Finite-Width Soil for a Rotating-Base Retaining Wall

by Zeyue Wang, Xinxi Liu, Weiwei Wang, Ziyu Tao and Song Li

Sustainability 2022, 14(15), 9772; https://doi.org/10.3390/su14159772 - 08 Aug 2022

Cited by 1 | Viewed by 1857

Abstract

In this study, we evaluated the active earth pressure on a retaining wall with a narrow cohesive fill under the rotation about the base mode. Under these conditions, Rankine’s and Coulomb’s earth pressure theories are not strictly effective. To improve the traditional earth [...] Read more.

In this study, we evaluated the active earth pressure on a retaining wall with a narrow cohesive fill under the rotation about the base mode. Under these conditions, Rankine’s and Coulomb’s earth pressure theories are not strictly effective. To improve the traditional earth pressure calculation methods (Rankine and Coulomb methods) and deduce the active earth pressure under the rotation about the base mode, here, we propose a new calculation method that incorporates the effects of wall displacement, soil arching and soil cohesion using inclined thin-layer elements. The calculation results are in good agreement with the model test data. Based on the parameter analysis, a critical aspect ratio of B/H = cotβ is determined along with a detailed elucidation of the various influencing factors (such as aspect ratio, cohesion and friction angle). The paper presents several solutions to improve the stability and lower the costs of retaining walls. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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11 pages, 3098 KiB

Open AccessArticle

Combined Treatment of Cr(VI)-Contaminated Soils by Reduction, Adsorption, and Solidification

by Yongxin Ji, Wenjie Zhang, Yu Xiao, Hong Jiang and Liaoyu Ye

Sustainability 2022, 14(14), 8827; https://doi.org/10.3390/su14148827 - 19 Jul 2022

Viewed by 1114

Abstract

Remediation of Cr(VI)-contaminated soil usually includes reducing Cr(VI) to Cr(III) with sub-sequent solidification. In this paper, a treatment technique that combines reduction, adsorption, and solidification was proposed. By introducing an adsorbent into the reduction process, the remediation effectiveness was improved and the amount [...] Read more.

Remediation of Cr(VI)-contaminated soil usually includes reducing Cr(VI) to Cr(III) with sub-sequent solidification. In this paper, a treatment technique that combines reduction, adsorption, and solidification was proposed. By introducing an adsorbent into the reduction process, the remediation effectiveness was improved and the amount of reducing and solidified agent was decreased. Synthetic precipitation leaching procedure (SPLP), unconfined compressive strength (UCS) test, and scanning electron microscope (SEM) analysis were carried out to evaluate the remediation effect under different agent combinations and different agent-adding procedures. The results of SPLP showed that the reduction/adsorption/solidification treatment significantly reduced the leachability of Cr. UCS increased with increasing dosage of cement and CaS₅, and decreased with an increasing dosage of vermiculite. The best agent dosage was CaS₅ of 2 times molar stoichiometric ratio of Cr(VI), 15% of vermiculite, and 20% of cement. Orthogonal test showed that for soil with low Cr(VI) content, CaS₅ dosage was the most important factor that affected the leachability of Cr. Cement and vermiculite have greater impact in limiting the leachability of Cr when Cr(VI) content in soil increased. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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18 pages, 9693 KiB

Open AccessArticle

Behavior Investigation of Necking Pile with Caps Assisted with Transparent Soil Technology

by Xudong Le, Xiuqin Cui, Mengyang Zhang, Zhijun Xu and Lin Dou

Sustainability 2022, 14(14), 8681; https://doi.org/10.3390/su14148681 - 15 Jul 2022

Cited by 2 | Viewed by 1323

Abstract

Pile easily develops necking defects during construction, which can limit the exertion of shaft resistance, resulting in reducing ultimate bearing capacity and creating potential safety hazards to projects. Based on transparent soil technology, this paper took the necking located in the middle part [...] Read more.

Pile easily develops necking defects during construction, which can limit the exertion of shaft resistance, resulting in reducing ultimate bearing capacity and creating potential safety hazards to projects. Based on transparent soil technology, this paper took the necking located in the middle part of pile shafts as an example and carried out vertical loading experiments on one intact pile and nine necking piles with caps. Then, the influences of necking length and diameter on the vertical bearing capacity were studied. The speckle field of the soil around piles was processed using the MatPIV program to investigate soil displacement. Through comparison and analysis with the intact pile, the reasons for the reduction in bearing capacity were obtained. The results show that the bearing capacity of the piles is seriously damaged by the necking. When the necking diameter is 4 mm and the necking length is 20 mm, the loss of vertical bearing capacity was 26.6%. The vertical bearing capacity decreases with the increase in necking length or the decrease in necking diameter. Pile necking makes a significant contribution to the displacement of soil around the cap. Inclined downward displacement of soil occurs near necking, which reduces the relative displacement between pile and soil and leads to the loss of pile resistance. For the necking with a large size, the soil displacement at the necking and around the pile cap is connected, which causes the displacement range of the soil under the pile cap to increase, resulting in a weakening of the exertion of shaft resistance. Subsequently, the vertical bearing capacity of piles is reduced. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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17 pages, 6344 KiB

Open AccessArticle

Analysis of Shear Resistance and Mechanism of Construction and Demolition Waste Improved by Polyurethane

by Qiang Ma, Junhui Li, Shaoping Huang and Henglin Xiao

Sustainability 2022, 14(13), 8180; https://doi.org/10.3390/su14138180 - 05 Jul 2022

Viewed by 1447

Abstract

A large amount of construction and demolition waste (CDW) is generated during the construction of projects. In this paper, polyurethane foam adhesive (PFA) was used to improve the mechanical properties of CDW. The large-scale direct shear tests, California bearing ratio (CBR) tests and [...] Read more.

A large amount of construction and demolition waste (CDW) is generated during the construction of projects. In this paper, polyurethane foam adhesive (PFA) was used to improve the mechanical properties of CDW. The large-scale direct shear tests, California bearing ratio (CBR) tests and Scanning electron microscope (SEM) tests were carried out to study the variation regularities of mechanical properties of treated CDW during the laboratory tests. The test results show that the shear strength of CDW increases with the increase of PFA content, vertical pressure and the shear rate. However, the increase of vertical pressure on the shear strength of CDW is smaller than that of PFA, and the improvement of the shear rate is relatively small. The California bearing ratio (CBR) test also proves that PFA can effectively improve the bearing capacity of CDW and reduce the loss of CBR caused by the 4-day soaking. Scanning Electron Microscope (SEM) finds that polyurethane wraps multiple particles and enhances the internal connection, which results in the cohesion between the particles being greatly increased. The study presented in this paper will better assess the shear resistance of improved CDW with PFA as a substitute for pavement base materials in practical engineering applications. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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16 pages, 6790 KiB

Open AccessArticle

Laboratory Model Tests of Leachate Drawdown Using Vertical Drainage Wells with Vacuum Pumping in Municipal Solid Waste Landfills with High Leachate Levels

by Xiaobing Xu, Guangyao Li, Da Ni, Cheng Feng and Sifa Xu

Sustainability 2022, 14(13), 8101; https://doi.org/10.3390/su14138101 - 02 Jul 2022

Cited by 3 | Viewed by 1486

Abstract

Municipal solid waste (MSW) landfills in China generally have high leachate mounds, which potentially induce severe geotechnical and environmental issues. In this study, laboratory model tests were carried out to preliminarily investigate the performance of vertical drainage wells accompanied with vacuum pumping (VDW-VP) [...] Read more.

Municipal solid waste (MSW) landfills in China generally have high leachate mounds, which potentially induce severe geotechnical and environmental issues. In this study, laboratory model tests were carried out to preliminarily investigate the performance of vertical drainage wells accompanied with vacuum pumping (VDW-VP) on leachate drawdown in MSW landfills with high leachate levels. Leachate drawdown tests through VDW-VP under conditions with and without gas injection were performed. Different vacuum pressures (0~−9.5 kPa) were imposed during the tests. Results indicated that the leachate pumping processes for both the two conditions were characterized by a stage of continuous effluent followed by a stage of discontinuous effluent, corresponding to the periods before and after the leachate level in the vertical well dropped to the bottom, respectively. During the stage of continuous effluent, as the vacuum pressure increased, the effluent rate decreased and the leachate level in the vertical well needed a longer time to reach the bottom. During the stage of discontinuous effluent, the leachate level in the MSW gradually approached that in the vertical well. A higher vacuum pressure rendered a larger cumulative leachate pumping volume for the condition with a gas injection, but this was not the case for the condition without a gas injection. In addition, some local pore water pressures were observed to suddenly increase and drop under the condition with the gas injection, attributed to the migration of entrapped gas zones. The increase in vacuum pressure might promote the migration of entrapped gas zones and hence increase the cumulative leachate pumping volume. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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19 pages, 7346 KiB

Open AccessArticle

The Π-Formed Diaphragm Wall Construction for Departure and Reception of Shield Machine

by Rui Huang, Jun Hu, Jingbo Pan, Yuwei Wu, Xingyue Ren, Dongling Zeng, Zhixin Wang and Shucheng Wang

Sustainability 2022, 14(13), 7653; https://doi.org/10.3390/su14137653 - 23 Jun 2022

Cited by 1 | Viewed by 1789

Abstract

In the design of shield tunnels, it is important to determine the structure of the diaphragm wall in order to achieve the required retaining wall structure pattern. In this paper, the stabilization effect of a new diaphragm wall structure (Π-formed diaphragm wall) is [...] Read more.

In the design of shield tunnels, it is important to determine the structure of the diaphragm wall in order to achieve the required retaining wall structure pattern. In this paper, the stabilization effect of a new diaphragm wall structure (Π-formed diaphragm wall) is investigated based on model experiments and numerical simulations. By varying the length of the wing wall and its angle to the end wall, it is possible to discuss the effect of different styles of Π-formed diaphragm wall on the support of the soil behind the wall during the departure and reception of the shield machine, the effect of the wing wall on the internal force distribution of the diaphragm wall generated during excavation, the effect of the excavation of the shield machine on the internal force distribution of the diaphragm wall, and the ground settlement during the departure and reception of the shield machine in different construction stages. Π-formed diaphragm walls can effectively support the soil behind the wall and reduce the major principal stresses generated during excavation. The maximum value of the major principal stress in the wing wall of the Π-formed diaphragm wall increases with the length of the wing wall, and the damage to the concrete of the diaphragm wall tends to occur on the outside rim of the wing wall. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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13 pages, 2967 KiB

Open AccessArticle

Centrifuge Modeling of Chloride Ions Completely Breakthrough Kaolin Clay Liner

by Xing Zeng, Jia Su, Hengyu Wang and Tong Gao

Sustainability 2022, 14(12), 6976; https://doi.org/10.3390/su14126976 - 07 Jun 2022

Cited by 2 | Viewed by 1293

Abstract

The 2 m thick compacted clay liner with a permeability coefficient of 1 × 10⁻⁷ cm/s is required in the Chinese technical specifications about landfills. The processes of chloride ion completely breakthrough low permeability barriers (k ≤ 1 × 10 [...] Read more.

The 2 m thick compacted clay liner with a permeability coefficient of 1 × 10⁻⁷ cm/s is required in the Chinese technical specifications about landfills. The processes of chloride ion completely breakthrough low permeability barriers (k ≤ 1 × 10⁻⁷ cm/s) were modeled at 50 g in a geo-centrifuge. A measuring system was used to monitor solute velocity and conductivity. The entire process of chloride ion completely breaking through 2 m Kaolin clay liner was modeled successfully, which provided a valuable testing technology for centrifuge modeling of contaminant transport through low-permeable clay. The analyses results indicated the breakthrough time of conservative pollutant for the 2 m clay liner with a hydraulic conductivity of 1.0 × 10⁻⁹ m/s under Δh_w of 40 m was 1.6 years. As for strongly adsorptive pollutants, the breakthrough time t_0.1 increased by 9 times when R_d increased from 1 to 10, which indicates that the effect of R_d on the performance of the liner was significant. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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19 pages, 2567 KiB

Open AccessArticle

Study on Properties of Copper-Contaminated Soil Solidified by Solid Waste System Combined with Cement

by Lisheng Liang, Jieya Zhang, Peiying Fang and Chongxian Suo

Sustainability 2022, 14(9), 5604; https://doi.org/10.3390/su14095604 - 06 May 2022

Cited by 4 | Viewed by 1778

Abstract

Three industrial solid wastes including red mud, carbide slag, and phosphogypsum combined with ordinary Portland cement were used as curing agents to solidify/stabilize loess polluted by a high concentration of copper ions. The unconfined compressive strength, resistivity, permeability coefficient, copper ion leaching concentration, [...] Read more.

Three industrial solid wastes including red mud, carbide slag, and phosphogypsum combined with ordinary Portland cement were used as curing agents to solidify/stabilize loess polluted by a high concentration of copper ions. The unconfined compressive strength, resistivity, permeability coefficient, copper ion leaching concentration, pH value, and other engineering application evaluation indexes were analyzed to preliminarily assess the applicability of the curing agent in the remediation of soil contaminated with a high concentration of copper ions. The mineral phases and functional groups of solidified soil were detected using XRD and FTIR, showing that the strength, electrical resistivity, and pH value of solidified soil decrease following the addition of copper ions. Moreover, the strength and resistivity of solidified soil increase with the curing age, and the pH value decreases with age. For solidified contaminated soil, when the total content of curing agent increases from 10 to 20%, the maximum 28 d strength increases from 1.35 to 5.43 MPa, and in this study, its permeability coefficient, copper ion leaching concentration, and pH value were found to be within the limits set by relevant national standards. In conclusion, red mud-carbide slag-phosphogypsum combined with cement has a good stabilizing effect on sites polluted with a high concentration of copper ions. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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Review

Jump to: Research

23 pages, 4785 KiB

Open AccessReview

Soil Erosion Due to Defective Pipes: A Hidden Hazard Beneath Our Feet

by Pooya Dastpak, Rita L. Sousa and Daniel Dias

Sustainability 2023, 15(11), 8931; https://doi.org/10.3390/su15118931 - 01 Jun 2023

Cited by 2 | Viewed by 1645

Abstract

Sinkholes are a significant underground hazard that threatens infrastructure and lives and sometimes results in fatalities. The annual cost of sinkhole damages exceeds $300 million, although this estimate is likely underestimated due to the need for national tracking. Sinkholes can also alter natural [...] Read more.

Sinkholes are a significant underground hazard that threatens infrastructure and lives and sometimes results in fatalities. The annual cost of sinkhole damages exceeds $300 million, although this estimate is likely underestimated due to the need for national tracking. Sinkholes can also alter natural drainage patterns, leading to increased flood risk. While natural sinkholes occur, those in urban areas are predominantly manmade, caused by soil erosion from defective pipes, typically due to aging. Climate change, storm surges, and urbanization have accelerated subsidence in urban environments, posing greater risks to critical infrastructure and densely populated areas. Extensive research has focused on soil erosion in dams; however, this knowledge does not necessarily apply to erosion through orifices, where gravity and other factors play significant roles. This paper presents a critical literature review on internal soil erosion due to defective pipes (SEDP). The review highlights that hydraulic loading, backfill type, and pipe conditions (defect shape, size, and depth) influence SEDP. Key findings from experiments and numerical studies are summarized, while mechanisms and knowledge gaps are identified. However, it is concluded that the current understanding in this field remains limited, underscoring the urgent need for further experimental and numerical research to expand the knowledge base on SEDP. Full article

(This article belongs to the Special Issue Geotechnical and Geoenvironmental Engineering Approaches to Prevent Ground-Related Disasters)

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