Geotechnical Modeling and Intelligent Systems

Inhaltsverzeichnis

1. Frontmatter

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2. Study on the Influence of Pile Arrangement of Wet Sinking Loess Foundation on the Settlement of Outlet Tower Foundation

   • Open Access

   Haichen Zhang, Zihao Ren, Jiaming Li, Yahui Zi, Xu Xu

   Abstract

   Due to load variations and foundation disturbances, hydraulic buildings on self-weighting wet sinking loess foundations are vulnerable to uneven settlement, which compromises the project's structural safety. Understanding the settlement and settlement characteristics of a group pile foundation supporting a pumping station outlet tower structure under different load distributions and different pile spacing arrangements for a wet-submerged loess foundation is essential for future research. To simulate and analyze the effects of load and group pile spacing variations on the settlement characteristics of wet sinking loess foundations, the finite element simulation software ABAQUS was used in this study to build numerical simulation models of group pile foundations with pile spacing of 1.2, 1.6, and 2.0 m under variable load conditions. The research results indicate a positive correlation between the soil settlement of collapsible loess foundations and the magnitude of load pressure. Under various pile spacing configurations, the center of the bearing plate is where the foundation's maximum deformation settlement occurs, and 18 m below the surface is where the inflection point of the settlement change at the pile-soil contact region emerges. Uneven settlement will result in the distortion of the soil mass due to the pile group impact of the pile foundation. The foundation with 1.2 m pile spacing has the highest uneven settlement deformation, followed by 1.6 m pile spacing, and the settlement with 2.0 m pile spacing has the most consistent deformation. It is possible to analyze the uneven settlement of collapsible loess foundations and improve building design by using the research techniques and simulation results presented in this article as suggestions and references.

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3. Research on Intelligent Mining of Super-High Core Wall Dam Complex Soil Stockyard

   • Open Access

   Chao Hu, Jialin Yu, Guike Zhang, Zhongyao Wang

   Abstract

   This research takes the mining planning of complex soil yards and the dam construction process as research objects. Based on the spatial morphological characteristics of complex soil yards, the three-dimensional models of the soil yards are established. Aiming at the multi-source and multi-dimensional data structure and type characteristics of soil material characteristics, the integration and unified management of soil material multi-source data are realized based on the data warehouse. The spatial interpolation algorithm was used to analyze and query the physical characteristics of soil material at any position. A virtual analysis model of soil material information system is constructed. Aiming at the characteristics of core wall filling construction process, a construction progress simulation model considering the impact of low temperature and rainy conditions on core wall filling was established, and the dynamic simulation of core wall construction progress with the filling layer as the basic unit, and its three-dimensional visualization display were realized. Based on the simulation data of the core wall filling process and considering the quality requirements of the core wall filling material, a dynamic planning model for the soil stockyard mining system was established, and the dynamic planning for the multi-material field earth material mining was realized. The above models and methods were verified on a practical project.

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4. Three-Dimensional Numerical Simulation Study on the Influence of Reservoir Water Level Variation on the Stability of Multiple Taluses

   • Open Access

   Zelin Zhou, Jie Zhang, Chao Feng, Maoyi Liu

   Abstract

   In order to investigate in-depth the impact of water level fluctuation on the stability of slopes with multiple accumulated deposits, this article takes the example of the deep accumulated deposits in Longwangxi. Based on the exploration of engineering geological conditions and the surrounding areas affected by historical landslides, a large-scale 3D numerical model is established to calculate the stability, deformation, and plastic zone variations of different accumulated deposits on the slope under different water level conditions through fluid-soil coupling analysis. The influence of water level changes on the stability of accumulated deposits is analyzed based on the numerical results. The analysis shows that when the water level is below the range of accumulated deposits, the impact of water level fluctuation on their stability can be neglected. However, as the water level rises above the range of accumulated deposits, significant deformations occur at the front edge of the deposits due to the softening and suspension-induced reduction in weight of the soil-rock mass, leading to even larger overall deformations of the accumulated deposits. In extreme cases, such as when the upstream reservoir gates of tributaries are opened, resulting in a sudden drop in water level, the entire slope of the accumulated deposits may become unstable. Furthermore, accumulated deposits located above the highest water level line may experience significant displacement due to disturbances caused by the instability of deposits below, thus indirectly affected by water level fluctuations.

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5. Compaction Quality Control of Soil-Rock Mixture Subgrade Based on DEM

   • Open Access

   Zhuoling He, Junyun Zhang, Xiaolong Luo, Tao Yang, Xiaofei Wu, Le Zhang

   Abstract

   Over-compaction or under-compaction of soil-rock mixture subgrade could lead to diseases after the expressway is put into service. Selecting the appropriate compaction process and compaction quality testing method is the key to controlling the compaction quality of soil-rock mixture subgrade. Based on continuous compaction control technology, the subgrade porosity under rolling was simulated by two-dimensional discrete element method, considering lay thickness, roller mass, and roller passes. The suitable filler type and recommended compaction process for the soil-rock mixture subgrade in Xingtai Section of Taihangshan Expressway were given: the lay thickness of soil-rock mixture subgrade is 0.6–0.7 m; the mass of the roller is 26 t, and the number of roller passes is rolled 5–6 passes. The evolution law of the subgrade porosity considering the particle crushing was analyzed. A method to control the compaction quality of the soil-rock mixture subgrade was proposed: whether the average difference between the in-site measurements from the last two roller passes exceeded 1% of the average value of the last pass.

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6. Analysis of the Influence of Deep Soft Soil Foundation Cofferdam Filling on Lateral Compression of Bridge Pile Foundations

   • Open Access

   Ruiqi Zhang, Aimin Liu, Guoliang Ye, Xu Liu

   Abstract

   In order to prevent seawater from flowing back into cities, road construction in Indonesia's coastal areas often requires the construction of breakwaters on the outside of bridges. The area is widely distributed on deep soft foundations, and the foundation soil at the breakwater is reinforced using the preloading method. The road is built on friction prefabricated pipe piles as the bridge foundation. Using PLAXIS 3D to analyze the beneficial effects of bamboo piles and bamboo rafts as working cushion layers on the filling of deep soft soil foundation and the settlement and deformation characteristics of the foundation, and simulating the adverse effects of lateral compression on the bridge pile foundation caused by the soft soil foundation under different loading conditions of the sea embankment. The results show that the flexible working cushion layer of bamboo piles and bamboo rafts is conducive to improving the loading stability of the soft soil foundation, when the second layer of pile is consolidated and stabilized before carrying out bridge pile foundation construction, the lateral compression generated by the soil will be smaller.

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7. Drilling Optimization Using Digital Image Stratigraphic Modeling

   • Open Access

   Zhengqiang Zeng, Yongchang Cai

   Abstract

   How to use survey data to build digital stratigraphic models, assess the uncertainty of models, and provide reasonable survey optimization schemes is one of the important tasks in the digital analysis of geotechnical engineering. This article offers a digital modeling concept based on surface and borehole data, with digital images as the medium. It uses the standard deviation of Kriging prediction to establish the twin-error map of the digital strata, and evaluates the uncertainty of the stratum boundaries using this twin-error map as an indicator of the accuracy of the digital strata. In addition, based on the proposed model concept, a sequential borehole optimization method based on the column error rate indicator is proposed. Case analysis shows that the sequential borehole optimization method, based on the digital stratigraphic model, significantly improves the refinement of the geological model and more effectively reduces the uncertainty of the digital model compared to conventional distance-based borehole arrangements.

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8. Research on the Influence of Ultra-Deep Foundation Pit Excavation on Adjacent Existing Tunnels and Deformation Control

   • Open Access

   Youpeng Wen, Mingxing Zhu, Kunpeng Wu, Xiaocong Liang, Xiaozhou Yan

   Abstract

   In view of the safety issues of subway tunnel proximity construction, taking a subway station pit project as an example, through the analysis of in situ measured data, the deformation impact of deep foundation pit excavation on the adjacent existing subway tunnel and the surrounding soil was studied, and numerical simulation to study the control effect of setting isolation piles, increasing the rigidity of the support in the pit, and unloading the soil above the tunnel on the deformation of the adjacent tunnel caused by the excavation of the foundation pit was used. The study shows that setting isolation piles near the tunnel side can effectively reduce the tunnel displacement, and the length of isolation piles should at least cover the bottom range of the tunnel. The support in the pit within the elevation of the tunnel section has a greater impact on the tunnel deformation, and enhancing the stiffness of the support or increasing the number of the supports in this range can effectively control the deformation of the tunnel as well. Unloading of the soil above the tunnel also has a significant effect on the vertical displacement of the tunnel, and it is recommended to adopt graded unloading in several layers to avoid one-time and massive-quantity unloading during the construction process.

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9. Analysis of Stability of Surrounding Rock in the Blasting Excavation of Pumped Storage Power Station Powerhouse

   • Open Access

   Xiji Li, Shuangquan Xu, Chuncheng Ma, Fan Zhang

   Abstract

   Cave excavation in the pumped storage power plant building is usually carried out by the technique of drilling and blasting. In this study, a part of the pumped storage power plant building was analyzed by the blasting simulation with the Ls-Dyna. Three different explosive arrangements were considered, and comparative analyses of the damage and cumulative effects on the surrounding rock were carried out, including blasting effects, damage analysis, and stress response. The results show that the blasting effects of three arrangements are basically similar and meet the requirements of excavation blasting for the project. However, compared with Cases 1 and 3, the damage level of Case 2 (cruciform arrangement) on the perimeter rock was reduced by 22.3 and 29.5%, respectively. The pressure waves generated by the blast were less superimposed and caused less damage to the upstream and downstream protective layers. Therefore, Case 2 represents the best explosive arrangement for blasting machinery room, which can minimize damage and ensure safety and stability during excavation and blasting.

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10. Discussion of the Collapsibility of Loess after Pre-Immersion Water Treatment

    • Open Access

    Bai He, Bin Zhi, Tiantian Wei

    Abstract

    To understand the effect of eliminating collapsibility and the change of soil structure after soaking treatment in the process of treating collapsible loess foundation with pre-soaking method, the indoor collapsibility test and scanning electron microscope (SEM) scanning test were carried out after washing and losing water treatment of soil at different depths, and the collapsibility and SEM images of undisturbed loess and soaking losing water loess at various depths were obtained. The results show that the shallow and deep strata can be divided according to whether the overlying strata's saturated self-weight pressure can reach the strata's initial collapsible pressure. The place where the saturated self-weight pressure of the overlying strata can go is deep strata, and vice versa. However, with the increase of burial depth, the decrease of porosity continues to increase, and the increase of initial collapsibility pressure tends to a fixed value and does not increase.

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11. Application of Building Information Modeling + Algorithm Model in the “Four Preparations” for Seepage Safety of Concrete Face Rockfill Dam

    • Open Access

    Yi Hou, Bin Mei, Jian Zhang, Wenyang Lin, Hong Yu

    Abstract

    Not only does China possess more than half of the total number of concrete face rockfill dams (CFRD) worldwide, but it has also experienced painful lessons regarding seepage stability control. Particularly, the continuous advancement of digital twin technology within the water conservancy industry offers diverse possibilities for emerging technologies to address traditional engineering difficulties. Against this backdrop, in combination with the engineering practice of Kaihua Reservoir, this paper creatively proposes a “four-preparation” method for the seepage safety of CFRDs based on the building information modeling+ (BIM+) algorithm model. Specifically, to begin with, this research constructs the BIM model applicable to the dam body and foundation in the design stage. Meanwhile, by integrating various information such as material parameters, this research further extracts the calculated cross-section from the model for the finite element seepage stability calculation and slice-method-based dam slope stability analysis, thereby improving the efficiency of design safety calculation. Furthermore, during the operation and management stage, by virtue of diverse technologies such as BIM, GIS, and IoT, this research implements the integration of security monitoring data with digital scenarios. In this foundation, this research establishes a confidence interval statistical model and corresponding graded warning indices through reorganization and analysis, thus forming a technical framework with algorithms for prediction, indices for pre-warning, scenarios for preview, and templates for pre-arranged planning, which furnishes support for engineering safety management.

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12. Study on the Secondary Lining Force of Soft Rock Tunnel with Large Deformation

    • Open Access

    Guize Liu, Changyi Yu, Shigang Liu, Yonghua Cao, Binbin Xu

    Abstract

    The secondary lining is not considered as a load-bearing structure in tunnel design. However, the current field measurements of tunnels show that the secondary lining is subjected to some load. Therefore, it is necessary to study the load sharing ratio of the secondary lining in detail. This paper analyzes the load sharing ratio of the secondary lining based on the thick-walled cylinder theory. Based on this theory, an observational design method and process for soft rock high-deformation tunnels are proposed, which integrate field measurements and consider the construction duration, facilitating design and construction. Additionally, the contact pressures between the surrounding rock, the initial support, and the secondary lining, were statistically analyzed for more than 60 tunnels. The statistical analysis shows that the worse the surrounding rock, the higher the contact pressure between the surrounding rock, the initial support, and the secondary lining. Finally, combining the field measurements of the Jingzhai tunnel and the thick-walled cylinder theory, the contact pressure of the secondary lining was determined to be 6110 kPa in the observational design, which is very close to the subsequent measured value of 6690 kPa, validating the effectiveness and accuracy of the proposed observational design method. The results of this paper provide reliable theoretical references and empirical guidance for the design and construction of tunnels.

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13. Construction Risk Assessment of Biogas Layer under Shield of Subway Tunnel

    • Open Access

    Dongyin Qi, Fei Yu

    Abstract

    The risk factors in the construction of subway shield tunnels have complex and variable characteristics. To address the impact of these characteristics in the evaluation process, a risk assessment method for subway tunnel shield tunneling through the biogas layer construction using WBS-RBS, AHP combined with cloud models is proposed. The WBS-RBS method is used to analyze the construction risk factors from the construction stage and 4M1E, and 24 risk indicators are identified. Use AHP to calculate the weight of risk indicators. Construction risk assessment model is constructed by cloud model theory to evaluate construction risk. Based on the construction project of Hangzhou–Haining Intercity Railway under biogas layer, this paper verifies the construction risk assessment method of subway tunnel under biogas layer with shield. The case study shows that the construction risk of biogas layer under the shield of Hangzhou–Haining Intercity Railway tunnel is medium risk. This paper provides reference value for the analysis and control of the construction risk factors of biogas layer under the shield of subway tunnel.

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14. Microstructure-Based Dynamic Characterization of Remodelled Loess under Traffic Loading

    • Open Access

    Hongtao Pei, Kebing Wen, Zezhan Shao, Shenqin Sun, Tianlu Xu, Junmin Pan

    Abstract

    As a common road subgrade fill in Northwest China, the dynamic properties of remoulded loess are the key to study the structural stability of loess subgrade, which is of great practical significance to the engineering construction and operation safety of roads in the corresponding region. This paper takes the remoulded loess of a roadbed in Shaanxi as the research object, and through the indoor dynamic triaxial test simulating traffic cyclic loading, the dynamic shear stress–shear strain relationship, dynamic shear modulus and damping ratio, and other dynamic characteristics of the soil under different water content, dry density and peripheral pressure are investigated and combined with the SEM test to qualitatively and quantitatively analyse the microstructural characteristics of the soil after vibration, so that the changes in dynamic characteristics of remoulded loess are caused by the microcosmic point of view. The results show that the dynamic shear stress–shear strain curve of the remoulded loess shows a hyperbolic development with an increase first and then a steady development, the dynamic shear modulus shows a sharp decrease at the beginning and a stable trend at the end with the shear strain, the increase of water content will lead to a decreasing trend of both, and the increase of dry density and peripheral pressure will lead to a corresponding increase of both. The test measured that the damping ratio changes in the range of 0.08–0.31 interval, showing a large increase in the initial period, the later interval fluctuation trend; the microstructure of the soil after vibration is studied, comparing the microscopic images and quantitative parameters under different test conditions, explaining the reasons for the change of the dynamics of remoulded loess through the change rule of the pore morphology and distribution, and providing the basis for the actual engineering.

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15. Analysis of Settlement Displacement of Tunnels Traversing Soft Soil Strata Containing Hazardous Gases

    • Open Access

    Jie He

    Abstract

    The tunnels may traverse soft soil strata rich in hazardous gases such as methane, which poses several adverse effects on construction. These effects primarily include excessive deformation of the tunnel, leakage, or migration of hazardous gases causing soil deformation and settlement, thereby negatively impacting shield tunneling operations; and the ingress of hazardous gases into the tunnel, which could lead to fires or explosions upon encountering an ignition source, as well as endangering the health of construction personnel within the tunnel. Therefore, this paper focuses on the critical technical issues associated with the construction of the B Line tunnel in the presence of hazardous gases. Utilizing numerical simulations, the uneven settlement and reinforcement techniques are analyzed for shield tunneling through hazardous gas-bearing strata. Based on a comprehensive geological investigation report, a robust finite element model of the tunnel has been developed. The implementation of reinforcement measures and strata stabilization techniques has proven effective under identical leakage conditions. The maximum displacement of the tunnel strata was reduced from the initial 2.0–1.5 mm, resulting in a 25% decrease in overall strata displacement. The findings will provide scientific basis and technical support for similar construction projects.

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16. Analysis of Deformation Influence of Gravel Shield Tunneling Under Existing Tunnel

    • Open Access

    Hongtao Pei, Rimei Han, Zezhan Shao, Shenqin Sun, Tianlu Xu, Junmin Pan

    Abstract

    In recent years, the rapid development of urban rail transit in China has led to an increasingly dense subway network. The construction of new subway tunnels frequently requires crossing many buildings in the city and existing infrastructure such as tunnels. Especially in the construction of Wumi Road Station of Kunming Metro Line 5, the construction phenomenon of crossing the existing structure is particularly significant. Based on this background, this paper uses the combination of model test and numerical simulation to explore the construction deformation law of shield tunneling under the existing tunnel in sandy cobble stratum of Kunming subway. After in-depth research on the three key factors of crossing angle, tunnel clearance, and formation loss rate, we have drawn the following conclusion: whether using a 60°oblique crossing method or a 90° straight crossing method when passing through the existing tunnel, their final impact on the surface and the existing tunnel is roughly the same. Further analysis reveals a significant negative correlation between the final deformation of the surface and existing tunnels, as well as the net distance between tunnels. That is, the larger the net distance between tunnels, the smaller the deformation; there is a positive correlation with the formation loss rate; that is, the higher the formation loss rate, the greater the deformation. With the increase of distance, the range of vertical deformation and surface settlement will also increase. In addition, there is a linear relationship between the formation loss rate and the final deformation value.

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17. Damage Characteristics of Fractured Rock Under Freeze–Thaw Cycle

    • Open Access

    Yuanqiang Lv, Jingang Zhao, Haibo Jiang

    Abstract

    Infrastructure construction and resource exploitation in cold areas are of great significance to social development. The freeze–thaw cycle experiment, uniaxial compression, CT scanning and frost heave force monitoring were carried out on the precast fissure red sandstone of slope in Fugu area of northern Shaanxi Province. Utilising three-dimensional reconstruction techniques, we analysed the dynamic mechanical properties of rock samples, considering both frost heave force monitoring and the uniaxial compression and CT scanning. By introducing the fractal dimension, we established a freeze–thaw load damage model for fractured sandstone. Furthermore, we conducted a correlation analysis between the micro- and macro-scales, aiming to explore the effects of freeze–thaw process on rock samples. With the increasing number of freeze–thaw cycles, the quality and wave velocity of water-saturated sandstone decrease significantly, which is mainly due to the gradual penetration of internal defects, which makes the originally tight particle structure become loose, and the water-saturated sandstone is not able to be removed. The originally tight particle structure become loose, and at the same time, the internal pores and micro-cracks expand and connect with each other. By conducting frost heave force monitoring and performing dynamic mechanical testing on sandstone samples, it is observed that the fracture part of sandstone presents a positive micro-strain due to the participation of water in the state of saturated water, and its peak strain gradually increases with the increase in freeze–thaw cycle.

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18. Research on a Machine Learning-Based Subgrade Compaction Degree Prediction Model

    • Open Access

    Feng Li, Jianfei Zhao, Hongzhao Li, Bing Hui, Zhenkun Wang, Wenjun Zhang, Guangbo Liu

    Abstract

    The highway subgrade is the foundation for ensuring the safe operation of highways, and subgrade compaction degree is a crucial parameter in subgrade construction. This study employs field tests to investigate subgrade compaction degree, analyzing the effects of rolling passes, rolling speed, and moisture content of subgrade fill material on subgrade compaction degree. Subsequently, four machine learning models are used to establish prediction models for subgrade compaction degree: random forest model, sparrow search algorithm optimized random forest model (SSA-RF), AdaBoost model, and BP-AdaBoost model. The results indicate that: (1) Subgrade compaction degree increases with the number of rolling passes, decreases with rolling speed, and is greater when the moisture content of the subgrade fill material is closer to the optimum moisture content. (2) The AdaBoost model shows the poorest prediction performance and is not suitable for predicting subgrade compaction degree, whereas the SSA-RF model achieves the best training results, with correlation coefficients (R²) of 0.98 and 0.94 for the training and testing sets, respectively, closely matching the actual results, validating the feasibility of this method for predicting highway subgrade compaction degree.

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