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CONTENTS
Volume 38, Number 3, August10 2024
 

Abstract
Because of the various patterns of deep-water inrush and complicated mechanisms, accurately predicting mine water inflows is always a difficult problem for coal mine geologists. In study presented in this paper, the water inrush channels were divided into four basic water diversion structures: aquifer, rock fracture zone, fracture zone and goaf. The fluid flow characteristics in each water-conducting structure were investigated by laboratory tests, and multistructure and multisystem coupling flow analysis models of different water-conducting structures were established to describe the entire water inrush process. Based on the research of the water inrush flow paths, the analysis model of different water inrush space structures was established and applied to the prediction of mine water inrush inflow. The results prove that the conduction sequence of different water-conducting structures and the changing rule of permeability caused by stress changes before and after the peak have important influences on the characteristics of mine water-gushing. Influenced by the differences in geological structure and combined with rock mass RQD and fault conductivity characteristics and other mine exploration data, the prediction of mine water inflow can be realized accurately. Taking the water transmitting path in the multistructure as the research object of water inrush, breaking through the limitation of traditional stratigraphic structure division, the prediction of water inflow and the estimation of potentially flooded area was realized, and water bursting intensity was predicted. It is of great significance in making reasonable emergency plans.

Key Words
broken rock mass; rough surface cracks; stress and strain; water conduction structure; water inflow prediction

Address
Jinhai Zhao , Weilong Zhu, Wenbin Sun,Hailong Ma and Hui Yang: State Key Laboratory Breeding Base for Mining Disaster Prevention and Control,
Shandong University of Science and Technology, Qingdao 266590, China;
College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China
Changbao Jiang: tate Key Laboratory Breeding Base for Mining Disaster Prevention and Control,
Shandong University of Science and Technology, Qingdao 266590, China;
College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
State Key Laboratory of Coal Mine Disaster Dynamics and Control, School of Resources and Safety Engineering,
Chongqing University, Chongqing 400030, China

Abstract
The use of lime stabilization and geosynthetic reinforcement is a common approach to improve the performance of fine-grained soils in geotechnical applications. However, the impact of this combination on the soil-geosynthetic interaction remains unclear. This study addresses this gap by evaluating the interface efficiency and soil-geosynthetic interaction parameters of lime-stabilized clay (2%, 4%, 6%, and 8% lime content) reinforced with geotextile or geogrid using direct shear tests at various curing times (1, 7, 14, and 28 days). Additionally, machine learning algorithms (Support Vector Machine and Artificial Neural Network) were employed to predict soil shear strength. Findings revealed that lime stabilization significantly increased soil shear strength and interaction parameters, particularly at the optimal lime content (4%). Notably, stabilization improved the performance of soil-geogrid interfaces but had an adverse effect on soil-geotextile interfaces. Furthermore, machine learning algorithms effectively predicted soil shear strength, with sensitivity analysis highlighting lime percentage and geosynthetic type as the most significant influencing factors.

Key Words
geosynthetic; interaction parameters; interface efficiency; lime stabilization; machine learning

Address
Khadije Mahmoodi: Department of Civil Engineering, Faculty of Engineering, Ardakan University, P.O. Box 184, Ardakan, Iran
Nazanin Mahbubi Motlagh: School of Civil and Environmental Engineering, UNSW Sydney, NSW, Australia
Ahmad-Reza Mahboubi Ardakani: Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, P.O. 16765-1719, Tehran, Iran

Abstract
In order to study the mechanical propertied and change rules of undrained shear behavior of saline soil under the freeze-thaw cycles, an improved constitutive model reflecting the effects of freeze-thaw cycles was proposed based on the traditional Duncan-Chang model. The saline soil in Qian'an County, western Jilin Province, was selected as the experimental object. Then, a set of freeze-thaw cycles (0, 1, 10, 30, 60, 90, 120) tests were conducted on the saline soil specimens, and conventional consolidated undrained triaxial shear tests were conducted on the saline soil specimens that underwent freeze-thaw cycles. The stress-strain relationship was obtained by the triaxial shear test. The model parameters have a corresponding regression relationship with the number of freeze-thaw cycles. Finally, based on the function expression of the model parameters, the modified Duncan-Chang model with the number of freeze-thaw cycles as the influence factor was established, whilst the calculation program of the modified model is compiled. Based on the test results, the stress-strain relationship of the saline soil specimen shows strain hardening. The shear strength gradually decreases with the increase of freeze-thaw cycle. The 10 freeze-thaw cycles are the turning point in the trend of changes of the mechanical properties of saline soils. The calculated and experimental stress-strain relationship are compared, and the comparison between the calculated value of the model and the experimental value showed that the two had a good consistency, which verified the validity of the modified Duncan-Chang model in reflecting the effects of the freeze-thaw cycle.

Key Words
Duncan-Chang model; freeze-thaw cycle; saline soil; stress-strain relationship; strain hardening

Address
Shukai Cheng: School of Civil Engineering and Architecture, Henan University of Science and Technology,
263 Kaiyuan Avenue, Luoyang 471000, China
Qing Wang and Yan Han: College of Construction Engineering, Jilin University, 938 West Minzhu Street, Changchun 130026, China
Jiaqi Wang: Changchun Institute of Technology, 395 Kuanping Road, Changchun 130103, China

Abstract
This study presents a groundbreaking analytical approach to find an exact solution for the bearing capacity of strip footings on reinforced slopes, utilizing the two-phase approach and slip line method. The two-phase approach is considered as a generalized homogenization technique. The slip line method is leveraged to derive the stress field as a lower bound solution and the velocity field as an upper bound solution, thereby facilitating the attainment of an exact solution. The key finding points out the variation of the bearing capacity factor N with influencing factors including the backfill soil friction angle, the footing setback distance from the slope crest edge, slope angle, strength, and volumetric fraction of inclusion layers. The results are evaluated by comparing them with those of relevant studies in the literature considering analytical and experimental studies. Through the application of the two-phase approach, it becomes feasible to determine the tensile loads mobilized along the inclusion layers associated with the failure zone. It is attempted to demonstrate the results by utilizing non-dimensional graphs to clearly illustrate variable impacts on reinforced soil stability. This research contributes significantly to advancing geotechnical engineering practices, specifically in the realm of static design considerations for reinforced soil structures.

Key Words
bearing capacity; exact solution; footings/foundations; reinforced soils; setback distance; slip line method; two phase approach

Address
Majd Tarraf and Ehsan Seyedi Hosseininia: Department of Civil Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract
This paper aims to explore the evolution of the pullout behavior of geocell reinforcement insights from three-dimensional numerical studies. Initially, a developed model was validated with the model test results. The horizontal displacement of geocells and infill sand and the passive resistance transmission in the geocell layer were analyzed deeply to explore the evolution of geocell pullout behavior. The results reveal that the pullout behavior of geocell reinforcement is the pattern of progressive deformation. The geocell pockets are gradually mobilized to resist the pullout force. The vertical walls provide passive pressure, which is the main contributor to the pullout force. Hence, even if the frontal displacement (FD) is up to 90m mm, only half of the pockets are mobilized. Furthermore, the parametric studies, orthogonal analysis, and the building of the predicted model were also carried out to quantitative the geocell pullout behavior. The weights of influencing factors were ranked. Ones can calculate the pullout force accurately by inputting the aspect ratio, geocell modulus, embedded length, frontal displacement, and normal stress.

Key Words
geocells; geosynthetics; predicted mode; pullout resistance

Address
Yang Zhao: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan 430071, China;
Xinjiang Transportation Planning Survey and Design Institute Co., Ltd., Urumqi 830006, China
Zheng Lu: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan 430071, China;
Hubei Key Laboratory of Geo-Environmental Engineering, Wuhan 430071, China
Jie Liu: Xinjiang Transportation Planning Survey and Design Institute Co., Ltd., Urumqi 830006, China
Jingbo Zhang: CCCC Second Highway Consultants Co., Ltd., Wuhan, 430056, China
Chuxuan Tang: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan 430071, China;
University of Chinese Academy of Sciences, Beijing 100049, China
Hailin Yao: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan 430071, China

Abstract
This study investigates the behaviour of hunchback retaining walls supporting unsaturated sandy backfill under active earth pressure conditions. Utilizing a horizontal slice method and a unified effective stress methodology, the influence of various factors on lateral earth pressure, including the position of the hunch along the wall, friction angles, and wall heights, is explored. The results suggest that relocating the hunch position from close to the wall's top to near its base leads to a significant decrease (ranging from 54% to 81%) in lateral earth pressure. However, as the hunch position transitions from near the top to mid-height, the point of application of active thrust shifts upward initially, then slightly downward as the hunch position approaches the toe. Notably, the reduction in lateral earth pressure is more pronounced for shorter wall heights and higher friction angles. Building upon these findings, an Artificial Neural Network (ANN)-based model is developed to accurately predict the lateral earth pressure coefficient and point of application, achieving R2 values of 0.94 and 0.93, respectively. In addition, an analytical model based on Coulomb's earth pressure theory is presented and compared with ANN models. These models are anticipated to assist designers and practitioners in optimizing hunchback retaining walls for unsaturated backfill.

Key Words
ANN; hunch back wall; method of horizontal slices; unsaturated soil

Address
Sivani Remash Thottoth and Vishwas N. Khatri: Department of Civil Engineering, IIT(ISM) Dhanbad, Jharkhand, 826004, India

Abstract
To get a better understanding of the effect of drying-wetting cycles (DWC) on the mechanical behaviors of silty clay hiving different initial moisture content (IMC), the direct shear tests were performed on sliding band soil taken from a reservoir-induced landslide at the Three Gorges Reservoir area. The results indicated that, as the increasing number of DWC, the shear stress-displacement curves type changed from strain-hardening to strain-softening, and both the soil peak strengths and strength parameters reduced first and then nearly remain unchanged after a certain number of DWC. The effects of DWC on the cohesion were predominated that on the internal friction angle. The IMC of 17% is regarding as the critical moisture content, and the evolution laws of both peak shear strength and strength parameters presented a reversed 'U' type with the rising of the IMC. Based on it, a strength deterioration evolution model incorporating the influence of IMC and DWC was developed to describe the total degradation degree and degradation rate of strength parameters, and the degradation of strength parameters caused by DWC could be counterbalanced to some extent as the soil IMC close to critical moisture content. The microscopic mechanism for the soil strength caused by the IMC and DWC were discussed separately. The research results are of great significance for further understanding the water-weakening mechanicals of the silty clay subjected to the water absorption/desorption.

Key Words
direct shear test; drying-wetting cycles; initial moisture content; sliding zone soil

Address
Shi-lin Luo: School of Civil Engineering, Changsha University, Changsha 410022, China, China;
College of Civil Engineering and Geomatics, Chang'an University, Xi'an 710064, China
Da Huang, Jian-bing Peng and Xiao-ran Gao: College of Civil Engineering and Geomatics, Chang'an University, Xi'an 710064, China
Fei Liu: School of Civil and Transportation Engineering, Henan University of Urban Construction, Pingdingshan 467000, China
Roberto Tomas: Dpto. de Ingenieria Civil. Escuela Politecnica Superior de Alicante. Universidad de Alicante, P.O. Box 99. E-03080, Alicante, Spain

Abstract
The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

Key Words
deep-buried tunnels; flexibility; mechanical model; pre-reinforcement; support pressure

Address
Jian Zhou and Yang Ding: Department of Civil Engineering, Hangzhou City University, Hangzhou 310015, China;
Key Laboratory of Safe Construction and Intelligent Maintenance for Urban Shield Tunnels of Zhejiang Province,
Hangzhou City University, Hangzhou 310015, China
Mingjie Ma, Luheng Li and Xinan Yang: The Key Laboratory of Road and Traffic Engineering, Ministry of Education, Tongji University, Shanghai 201804, China

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