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CONTENTS
Volume 21, Number 6, June25 2020
 

Abstract
This study evaluated the side resistance of drilled shafts socketed into rock sections. Commonly used analysis methods for side resistance of piles in rocks are examined by utilizing a large number of load test data. The analysis of the unit side resistance of pile foundations embedded into rock sections is based on an empirical coefficient (

Key Words
drilled shaft; load test; friction resistance; rock; rock quality designation

Address
Cheng-Chieh Hsiao, Anjerick J. Topacio and Yit-Jin Chen: Department of Civil Engineering, Chung Yuan Christian University, Chung-Li District, Taoyuan City 32023, Taiwan

Abstract
Slopes stabilised with piles are seldom analysed considering uncertainties in the parameters of the pile-slope system. Reliability analysis of the pile-slope system quantifies the degree of uncertainties and evaluates the safety of the system. In the present study, the reliability analysis of a slope stabilised with piles is performed using the first-order reliability method (FORM) based on Hasofer-Lind approach. The implicit performance function associated with the factor of safety (FS) of the slope is approximated using the response surface method. The analyses are carried out considering the design matrices formulated based on both the 2k factorial design augmented with a centre run (2k fact-centred design) and face-centered cube design (FCD). The finite element method is used as the deterministic model to compute the FS of the pile-slope system. Results are compared with the results of the Monte Carlo simulation. It is observed that the optimum location of the row of piles is at the middle of the slope to achieve the maximum FS. The results show that the reliability of the system is not uniform for different pile configurations, even if the system deterministically satisfies the target factor of safety (FSt) criterion. The FSt should be selected judiciously as it is observed that the reliability of the system changes drastically with the FSt level. The results of the 2k fact-centred design and FCD are in good agreement with each other. The procedure of the FCD is computationally costly and hence the use of 2k fact-centred design is recommended, provided the response of the system is sufficiently linear over the factorial space.

Key Words
slope stability; piles; uncertainty; reliability; Hasofer-Lind; finite element method; Monte Carlo simulation; response surface method; FCD; 2k factorial design

Address
Ramanandan Saseendran and Dodagoudar G. R.: Geotechnical Engineering Division, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai - 600036, India

Abstract
An elastic-plastic solution for cavity expansion problem considering strength degradation, undrained condition and initial anisotropic in-situ stress is established based on the Tresca yield criterion and cavity expansion theory. Assumptions of large-strain for plastic region and small-strain for elastic region are adopted, respectively. The initial in-situ stress state of natural soil mass may be anisotropic caused by consolidation history, and the strength degradation of soil mass is caused by structural damage of soil mass in the process of loading analysis (cavity expansion process). Finally, the published solutions are conducted to verify the suitability of this elastic-plastic solution, and the parametric studies are investigated in order to the significance of this study for in-situ soil test.

Key Words
Tresca yield criterion; cavity expansion; elastic-plastic solution; strength degradation; undrained condition; initial anisotropic in-situ stress; large-strain

Address
Chao Li, Jin-feng Zou and Yu-ming Sheng: School of Civil Engineering, Central South University, Hunan 410075, China

Abstract
The presence of cracks changes the water content pattern during seepage through a cracked soil as compared to that of intact soil. In addition, several different crack networks may form in one soil type. These two factors result in a variation of water contents in the soil matrix part of a cracked soil during seepage. This paper presents an investigation of the effect of crack network representation on the water content of the soil matrix part of cracked soil using numerical models. A new method for the numerical generation of crack networks incorporating connections among crack endpoints was developed as part of the investigation. Numerical analysis results indicated that the difference in the point water content was large, whereas the difference in the average water content was relatively small, indicating the uniqueness of the crack network representation on the average water content of the soil matrix part of cracked soil.

Key Words
water content; numerical model; drying; shrinkage; crack network; unsaturated soils

Address
Sugeng Krisnanto: Geotechnical Engineering Research Group, Faculty of Civil & Environmental Engineering, Bandung Institute of Technology, CIBE Building Level 5, Room CIBE 0506, Jalan Ganesha No. 10, Bandung 40132, Indonesia

Harianto Rahardjo: School of Civil & Environmental Engineering, Nanyang Technological University, Blk N1, #1B-36, 50 Nanyang Avenue, Singapore 639798

Eng Choon Leong: School of Civil & Environmental Engineering, Nanyang Technological University, Blk N1, #1C-80, 50 Nanyang Avenue, Singapore 639798



Abstract
High-stress and complex geological conditions impose great challenges to maintain excavation stability during deep underground mining. In this research, large anisotropic deformation and its management by support system at a deep underground mine in Western Australia were simulated through three-dimensional finite-difference model. The ubiquitous-joint model was used and calibrated in FLAC3D to reproduce the deformation and failure characteristics of the excavation based on the field monitoring results. After modeling verification, the roles of mining depth also the intercept angle between excavation axis and foliation orientation on the deformation and damage were studied. Based on the results, quantitative relationships between key factors and damage classifications were presented, which can be used as an engineering tool. Subsequently, the performance of support system installation sequences was simulated and compared at four different scenarios. The results show that, first surface support and then reinforcement installation can obtain a better controlling effect. Finally, the influence of bolt spacing and ring spacing were also discussed. The outcomes obtained in this research may play a meaningful reference for facing the challenges in thin-bedded or foliated ground conditions.

Key Words
large deformation; squeezing, intercept angle; ground reinforcement; ubiquitous-joint model; support standard

Address
Bo Hu: 1.) School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China
2.) Inner Mongolia Key Laboratory of Mining Pressure and Strata Control, Hulunbeir University, Hulunbeir 021008, China

Mostafa Sharifzadeh: 1.) Department of Mining Engineering, Western Australian School of Mines, Curtin University,Kalgoorlie 6430, Australia
2.) Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China

Xia-Ting Feng: Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China

Roo Talebi: Northern Star Resources Ltd, Kalgoorlie WA 6430, Australia

Jin-Fu Lou: Mining and Designing Branch, China Coal Research Institute, Beijing, China

Abstract
Large tonnage pile foundation load test system is designed in this paper by using pre-stressed technique to optimize the design of anchor pile reaction beam system, in which project pile can be successfully taken as anchor pile. The test results show that the cracks and excessive deformations of the prestressed anti-force device designed in this study have not occurred, and the prestressed tendons of the anchor pile ensure that the anchor pile will not be pulled and fractured, and the prestressed tendons can be reused, thus ensuring the safety and reliability of the test. This test method can directly test bearing capacity of long rock-socketed piles, and analysis bearing behaviors from test results of sensors which embedded in the pile. Through test studied, authors summarized the vertical bearing characteristics of long rock-socketed piles and the main problems that should be paid attention to during design and construction, and provided reliable solutions.

Key Words
load test system; long rock-socketed pile; vertical bearing capacity

Address
Xue-feng Zhang, Ying-sheng Ni and Chun-xia Song: Research Institute of Highway Ministry of Transport, M.O.T, Beijing, 100088, P.R. China

Dong Xu: Department of Bridge Engineering, Tongji University, Shanghai, 200092, P.R. China

Abstract
Aiming at the mechanical and structural characteristics of the contact zone composite rock, the uniaxial compression tests and numerical studies were carried out. The interaction forms and formation mechanisms at the contact interfaces of different materials were analyzed to reveal the effect of interaction on the mechanical behavior of composite samples. The research demonstrated that there are three types of interactions between the two materials at the contact interface: constraint parallel to the interface, squeezing perpendicular to the interface, and shear stress on the interface. The interaction is mainly affected by the differences in Poisson\'s ratio and elastic modulus of the two materials, stronger interface adhesion, and larger interface inclination. The interaction weakens the strength and stiffness of the composite sample, and the magnitude of weakening is positively correlated with the degree of difference in the mechanical properties of the materials. The tensile-shear stress derived from the interaction results in the axial tensile fracture perpendicular to the interface and the interfacial shear facture. Tensile cracks in stronger material will propagation into the weaker material through the bonded interface. The larger inclination angle of the interface enhances the effect of composite tensile/shear failure on the overall sample.

Key Words
contact zone composite sample; interface interaction; squeezing; derived stress; mechanical behavior

Address
Weiqi Wang, Binyu Luo, Jie Wang and Yang Liu: 1.) School of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430-081, P.R. China
2.) Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan, 430-081, P.R. China

Yicheng Ye and Qihu Wang: 1.) School of Resources and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430-081, P.R. China
2.) Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan, 430-081, P.R. China
3.) Industrial Safety Engineering Technology Research Center of Hubei Province, Wuhan 430-081, P.R. China

Abstract
This study is attempted to propose a new hybrid artificial intelligence model called integrative genetic algorithm with multivariate adaptive regression splines (GA-MARS) for settlement prediction of shallow foundations on sandy soils. In this hybrid model, the evolution algorithm – Genetic Algorithm (GA) was used to search and optimize the hyperparameters of multivariate adaptive regression splines (MARS). For this purpose, a total of 180 experimental data were collected and analyzed from available researches with five-input variables including the bread of foundation (B), length to width (L/B), embedment ratio (Df/B), foundation net applied pressure (qnet), and average SPT blow count (NSPT). In further analysis, a new explicit formulation was derived from MARS and its accuracy was compared with four available formulae. The attained results indicated that the proposed GA-MARS model exhibited a more robust and better performance than the available methods.

Key Words
multivariate adaptive regression spline; genetic algorithm; evolutionary hybrid model; settlement prediction; shallow foundation

Address
Nguyen-Vu Luat, Seunghye Lee and Kihak Lee: Department of Architectural Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea

Van-Quang Nguyen: Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, South Korea

Sungwoo Woo: TechSquare Ltd. South Korea, 25 Banpodae-ro, Seocho-gu, Seoul 06710, South Korea

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