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CONTENTS
Volume 20, Number 4, February25 2020
 

Abstract
Excavation usually induces considerable ground settlement in soft ground, which may result in damage of adjacent buildings. Generally, the settlement is predicted through elastic-plastic finite element method and empirical method with defects. In this paper, an analytical solution for predicting ground settlement induced by excavation is developed based on the definition of three basic modes of wall displacement: T mode, R mode and P model. A separation variable method is employed to solve the problem based on elastic theory. The solution is validated by comparing the results from the analytical method with the results from finite element method(FEM) and existing measured data. Good agreement is obtained. The results show that T mode and R mode will result in a downward-sloping ground settlement profile. The P mode will result in a concave-type ground settlement profile.

Key Words
excavation; ground settlement; retaining wall movement; analytical solution; displacement-controlled method

Address
Jiangu Qian, Yuanmeng Tong and Linlong Mu: 1.)Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
2.) Key Laboratory of Geotechnical and Underground Engineering of Ministy of Education, Tongji University, Shanghai 200092, China

Qi Lu: Hangzhou Qianjiang New City Construction Development Co., Ltd., Hangzhou 310000, China

Hequan Zhao: China Railway 14th Bureau Group Shield Engineering Co., Ltd, Nanjing, 210000, China

Abstract
This paper investigates the stability of a three-dimensional (3D) wedge under the pseudo-static action of an earthquake based on the nonlinear Barton-Bandis (B-B) failure criterion. The influences of the mechanical parameters of the discontinuity surface, the geometric parameters of the wedge and the pseudo-static parameters of the earthquake on the stability of the wedge are analyzed, as well as the sensitivity of these parameters. Moreover, a stereographic projection is used to evaluate the influence of pseudo-static direction on instability mode. The parametric analyses show that the stability coefficient and the instability mode of the wedge depend on the mechanical parameter of the rock mass, the geometric form of the wedge and the pseudo-static state of the earthquake. The friction angle of the rock φb, the roughness coefficient of the structure surface JRC and the two angles related to strikes of the joints θ1 and θ2 are sensitive to stability. Furthermore, the sensitivity of wedge height h, the compressive strength of the rock at the fracture surface JCS and the slope angle α to the stability are insignificant.

Key Words
three-dimensional rock wedge; pseudo-static stability analysis; nonlinear Barton-Bandis failure criterion; stereographic projection; design charts

Address
Lianheng Zhao: 1.) School of Civil Engineering, Central South University, Changsha, Hunan 410075, China
2.) Key Laboratory of Heavy-Haul Railway Engineering Structure, Ministry of Education, Central South University, Changsha, Hunan 410075, China

Kangfu Jiao, Shi Zuo, Chenghao Yu and Gaopeng Tang: School of Civil Engineering, Central South University, Changsha, Hunan 410075, China

Abstract
The aim of this paper was to investigating the effects of soil relative density, construction ‎materials roughness, oil type (gasoil, crude oil, and used motor oil), and oil content on the ‎internal and interface shear behavior of sand with different construction materials by means ‎of a modified large direct shear test apparatus. Tests conducted on the soil-soil (S-S), soil-‎rough concrete (S-RC), soil-smooth concrete (S-SC), and soil-steel (S-ST) interfaces and ‎results showed that the shear strength of S-S interface is always higher than the soil-material ‎interfaces. Internal and interface friction angles of sand beds increased by increase in ‎relative density and decreased by increasing oil content. The oil properties (especially ‎viscosity) played a major role in interface friction behavior. Despite the friction angles of ‎contaminated sands with viscous fluids drastically decreased, it compensated by the ‎apparent cohesion and adhesion developed between the soil grains and construction ‎materials. ‎

Key Words
internal and interface shear strength; sand; gasoil; crude oil; used motor oil; relative density

Address
Amirhossein Mohammadi and Mohammad Reza Boroomand: Department of Civil Engineering, Tafresh University, Tafresh, 3951879611, Iran

Taghi Ebadi: Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, 1591634311, Iran


Abstract
This study focuses on a prediction approach of compaction compensation grouting efficiency in sandy soil. Based on Darcy\'s law, assuming that the grouting volume is equal to the volume of the compressed soil, a two-dimensional calculation model of the compaction compensation grouting efficiency was improved to three-dimensional, which established a dynamic relationship between the radius of the grout body and the grouting time. The effectiveness of this approach was verified by finite element analysis. The calculation results show that the grouting efficiency decreases with time and tends to be stable. Meanwhile, it also indicates that the decrease of grouting efficiency mainly occurs in the process of grouting and will continue to decline in a short time after the completion of grouting. The prediction three-dimensional model proposed in this paper effectively complements the dynamic relationship between grouting compaction radius and grouting time, which can more accurately evaluate the grouting efficiency. It is practically significant to ensure construction safety, control grouting process, and reduce the settlement induced by tunnel excavation.

Key Words
compensation grouting; grouting efficiency; filtration; sandy soils; soil settlement

Address
Xiang-Hua Xu: Guizhou Provincial Communications Department, No. 66, Yan\'an West Road,Guiyang, Guizhou Province, People\'s Republic of China

Zhou-Chen Xiang, Jin-Feng Zou and Feng Wang: School of Civil Engineering, Central South University, No.22, Shaoshan South Road,
Central South University Railway Campus, Changsha, Hunan Province, People\'s Republic of China


Abstract
Pile foundation is widely used for railway bridges in loess throughout northwestern China. Modeling of the loess–pile interaction is an essential part for seismic analysis of bridge with pile foundation at seismically active regions. A quasi-static test is carried out to investigate the hysteretic behaviors of pile foundation in collapsible loess. The failure characteristics of the bridge pile-loess system under the cyclic lateral loading are summarized. From the test results, the energy dissipation, stiffness degradation and ductility of the pile foundation in loess are analyzed. Therefore, a bilinear model with stiffness degradation is recommended for the nonlinearity of the bridge pier-pile-loess system. It can be found that the stiffness of the bridge pier-pile-loess system decreases quickly in the initial stage, and then becomes more slowly with the increase of the displacement ductility. The equivalent viscous damping ratio is defined as the ratio of the dissipated energy in one cycle of hysteresis curves and increases with the lateral displacement.

Key Words
high-speed railway bridges; pile foundation; hysteretic behaviors; loess; loess-pile interaction

Address
Xingchong Chen, Xiyin Zhang,Yongliang Zhang, Mingbo Ding and Yi Wang: School of Civil Engineering, Lanzhou Jiaotong University, 88 Anning West Road, Lanzhou, Gansu, China

Abstract
Preventing or reducing the damage impact of lateral soil movements on piled foundations is highly dependent on understanding the behavior of passive piles. For this reason, a detailed experimental study is carried out, aimed to examine the influence of soil density, the depth of moving layer and pile spacing on the behavior of a 2x2 free-standing pile group subjected to a uniform profile of lateral soil movement. Results from 8 model tests comprise bending moment, shear force, soil reaction and deformations measured along the pile shaft using strain gauges and others probing tools were performed. It is found that soil density and the depth of moving layer have an opposite impact regarding the ultimate response of piles. A pile group embedded in dense sand requires less soil displacement to reach the ultimate soil reaction compared to those embedded in medium and loose sands. On the other hand, the larger the moving depth, the larger amount of lateral soil movement needs to develop the pile group its ultimate deformations. Furthermore, the group factor and the effect of pile spacing were highly related to the soil-structure interaction resulted from the transferring process of forces between pile rows with the existing of the rigid pile cap.

Key Words
pile group; lateral soil movements; model test; passive piles

Address
Ihsan Al-abboodi and Osamah Al-salih: Department of Civil Engineering, University of Basrah, Iraq

Tahsin Toma Sabbagh: School of Computing, Science and Engineering, University of Salford, Manchester, U.K.

Abstract
Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

Key Words
skirted foundation; machine foundation; dynamic impedance; finite element analysis; evolutionary polynomial regression analysis

Address
Saif Alzabeebee: Department of Roads and Transport Engineering, College of Engineering, University of Al-Qadisiyah, Al-Qadisiyah, Iraq

Abstract
Prestressed ground anchors are important structural elements in geotechnical engineering. Despite their widespread usage, the design process is often significantly simplified. One of the major drawbacks of commonly used design methods is the assumption that skin friction is mobilized uniformly along an anchor\'s fixed length, one consequence of which is that a progressive failure phenomenon is neglected. The following paper introduces an alternative design approach - a computer algorithm employing the load-transfer method. The method is modified for the analysis of anchors and combined with a procedure for the derivation of load-transfer functions based on commonly available laboratory tests. The load-transfer function is divided into a pre-failure (hardening) and a post-failure (softening) segment. In this way, an aspect of non-linear stress-strain soil behavior is incorporated into the algorithm. The influence of post-grouting in terms of radial stress update, diameter enlargement, and grout consolidation is included. The axial stiffness of the anchor body is not held constant. Instead, it gradually decreases as a direct consequence of tensile cracks spreading in the grout material. An analysis of the program\'s operation is performed via a series of parametric studies in which the influence of governing parameters is investigated. Finally, two case studies concerning three investigation anchor load tests are presented.

Key Words
ground anchor; pullout capacity; load-transfer method; progressive failure; grout

Address
Juraj Chalmovsky and Lumir Mica: Department of Geotechnics, Faculty of Civil Engineering, Brno University of Technology, Veveri 331/95, 602 00 Brno, Czech Republic

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