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CONTENTS
Volume 26, Number 4, August25 2021
 

Abstract
The Northwest Loess Plateau in China is mountainous and contains deep valleys which consist mostly of loess. Tunnels constructed in such deep valley and backfilled with soil are called high-filled cut-and-cover tunnels (HFCCT). Several studies have been conducted on HFCCT, but the creep behavior of loess backfill has not been fully explored. Post-construction settlement in loess is large, and it is difficult for stability to be reached in a short time. Therefore, it is necessary to predict long-term behavior of earth pressure around an HFCCT to ensure long-term safety. The primary purpose of this paper is to investigate changes in earth pressure and displacement of soil with time after the completion of the backfill process. This is achieved using FLAC3D software (finite difference method). The results show that discrepancies in soil settlement and surface settlement will gradually increase and eventually reach stability. The distribution and value of earth pressure also becomes redistributed. Meanwhile, influencing factors such as slope angle and valley width gradually weaken with time, and only affect the time needed to reach stability.

Key Words
creep; earth pressure; FLAC3D; high-filled cut-and-cover tunnel (HFCCT); post-construction settlement

Address
Sheng Li and Guixia Ning: College of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu, China

Yuchi Jianie: Kunming Survey, Design and Research Institute Co., Ltd. of China Railway Eryuan Engineering Group, Kunming, Yunnan, China

I-Hsuan Ho: Harold Hamm School of Geology and Geological Engineering, University of North Dakota, 81 Cornell St. Stop. 8358, Grand Forks, ND 58202, U.S.A.

Changdan Wang: Department of Urban Rail Transit and Railway Engineering, College of Transportation Engineering, Tongji University, Shanghai, China

Abstract
The effect of ladle furnace slag or LFS on the mechanical properties of the lateritic soil mixes for use as a subbase course material in the pavement structure was investigated. The lateritic soil grade E with the lowest mechanical properties was studied by mixing the LFS in the ratios of 5 to 12 wt%. The pavement material criterion of the Thailand Department of Highways was used to qualify the liquid limit, plasticity index, the California bearing ratio, and the swelling index of the mixed lateritic soil with the LFS. An increase in the California bearing ratio of the lateritic soil under the soaked condition was found to be positively correlated with the increasing LFS. Meanwhile, the liquid limit and the plasticity index decreased, leading to a decrease in the swelling index of the lateritic soil containing LFS. Using LFS reduced the total fine-particle ratio in the soil mixture but effectively enhanced the degree of compaction and swelling tolerance in the lateritic soil mixture. 10 wt% LFS is strongly recommended as a minimum admixture in the lateritic soil due to the highly improved plasticity and the mechanical properties of the lateritic soil for a subbase course material selection under the standard specifications.

Key Words
ground improvement; pavement; reinforced soil; slag; soil stabilization

Address
Salisa Chaiyaput: Department of Civil Engineering, School of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand

Jiratchaya Ayawanna: School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

Abstract
The excess pore pressure increases under undrained cyclic loading which cause decrease in effective stress followed by possible failure in the soft soil. With the inclusion of vertical drains radial drainage allows quick dissipation of excess pressure during cyclic loading and thereby failure of foundation soil may be avoided. The present study aims for analytical closed-form investigation on soft cohesive deposit under radial flow consolidation through vertical drains with no smear when subjected to long-term rapid cyclic loading. The mathematical formulation of pore pressure including degree of consolidation under cyclic loading is developed by using Green

Key Words
cyclic stress ratio; effective confining pressure; frequency; number of cycles; plasticity index; pore water pressure; radial consolidation

Address
Monideepa Paul: Department of Civil Engineering, Heritage Institute of Technology, Kolkata-700107, India

Kaustav Bakshi: Department of Civil Engineering, Indian Institute of Technology Indore, Madhya Pradesh 452020, India

Ramendu Bikas Sahu: Department of Civil Engineering, Jadavpur University, Kolkata- 700032, India

Abstract
There exists large volume of marine dredged clay generated worldwide to potentially compromise to ocean environment. Efficient resource utilization of dredged clay is crucial to sustainable development of offshore works. In this study, cement-treated marine dredged clay is suggested as filling materials for the construction of artificial islands in Dalian Bay, China. To evaluate influence of cement addition on compressibility, a series of oedometer tests were performed on reconstituted and cement-treated dredged clay. The effects of initial water content, cement content and curing time were examined. In addition, the pore fluid salinity effect on reconstituted and cemented dredged clay was explored by desalination treatment, respectively. The testing results show that the vertical yield stress of cemented dredged clay is governed by initial water content while the compressibility in post-yield state is determined by cement content. The influence of curing time is more significant for the specimens with higher initial water content. The compressibility of reconstituted dredged clay decreases when increasing salinity of pore fluid, but pore salt accelerates the degradation of artificial structure of cemented clay. Moreover, a practical predicting method was presented based on the experimental data. Both the pre-yield compression index Cs and post-yield compression index Cc are correlated with the yielding point. The proposed method enables to more quickly capture the compression curves of cement-treated dredged clay in practice.

Key Words
cement-treated; compression behavior; marine dredged clay; pore fluid salinity; predicting method

Address
Jianwen Ding, Xing Wan, Jianhua Wang, Cong Mou and Mengying Gao: Department of Underground Engineering, Southeast University, NO.2 Southeast University Road, Jiangning District, Nanjing, China


Abstract
Under compression, the flaws in soils will not only weaken the mechanical properties of soils, but also affect the strain localization of soils. In order to study the influence of flaws on the behavior of soils under compression, the uniaxial compression tests of clays with different inclination and position fissures were carried out, and the two-dimensional numerical analysis was also discussed based on the damage plasticity model. Analyzing the results of the uniaxial compression test and simulation of the intact and fissured clays, the following conclusions can be drawn: (1) The 60-degree fissure located on the upper position of the right edge of the clay has the greatest influence on the failure form and damage energy of clays, which can reduce the compression strength by 30% compared with that of the intact clay. (2) The numerical method based on the damage plasticity model can basically simulate the compression behavior of clays containing a pre-existing fissure and reproduce the failure characteristics of clays. (3) The preset fissure has obvious influence on the evolution of maximum principal stress in the area with serious damage, but less on the shear stress. And in the area with slight damage, the effect on the maximum principal stress and shear stress is very weak.

Key Words
failure; fissured clay; local damage; numerical simulation; uniaxial compression

Address
Wei Wang, Binghua Zhao, Aiyu Hu and Jibin Shang: School of Civil Engineering, Nanjing Institute of Technology, Nanjing 211167, China

Abstract
Arching effect is a universal phenomenon of the load transfer mechanism which is visually observed in the heaps of granular material. In this study, we adopt geometrically non-linear isogeometric finite element analysis to revisit the theoretical concept of the arching effect in the granular sand piles under base deflection with an assumption of elastic continuum theory. Through two studies of the planar and conical sand heaps, this work expects to supply the numerical results for double-checking some simple benchmarks before extending to the complicated problems. Herein, the reliability and accuracy of the present model are validated by checking the weight balance condition and comparing with some available literature. The numerical results demonstrate that the stress dip accompanying a significant shear stress mobilization at the base is formed immediately once the base deflection occurs. Furthermore, the trajectories of principal stresses are plotted to visually manifest the force propagation in the sand piles which enables us to explain the formation and shape of the arching effect.

Key Words
arching effect; base deflection; geometric non-linearity; sand piles; stress dip

Address
Tan Nguyen: Sustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering,
Ton Duc Thang University, Ho Chi Minh City, Vietnam

Loc V. Tran: Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Abstract
More and more attention is paid to the stability, safety and comfort of trains during its operation stage. When the train is running, in addition to the track gravity, it is also affected by the train load and earthquake, these dynamic effects will have a certain impact on the normal operation of the railway. However, the current research on the dynamic response of composite CFG and cement-soil compaction piles foundations under dynamic loads is rarely involved. Taking the composite foundation of Baoji-Lanzhou Passenger Dedicated Line as the research object, the dynamic response of the composite foundation under train load, seismic wave and train-seismic load is analyzed in detail by using numerical simulation software. The results show that under the train load, the maximum displacement occurs at the action position of the train load, and it is gradually reduced downward. The overall displacement is not large, and the influence on the operation of the train is little. Under earthquake action, the displacement is the largest at the bottom of subgrade, and gradually decreases upward, which has little effect on the top of embankment. Under the train-earthquake action, the displacement of subgrade bottom and embankment top is larger, and gradually decreases to the middle. It provides the corresponding theoretical basis for the same type of railway subgrade engineering.

Key Words
CFG and cement-soil compaction pile; composite foundation; dynamic response; numerical simulation; seismic wave

Address
Xuansheng Cheng, Xiangdong Cai, Xiaoyan Zhang and Lijun Gong: 1.) Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education,
Lanzhou University of Technology, Lanzhou, 730050, PR China
2.) School of Civil Engineering, Lanzhou University of Technology, Lanzhou, 730050, PR China

Jianchao Chen: School of Civil Engineering, Lanzhou University of Technology, Lanzhou, 730050, PR China

Chengyue Gu: China Railway 21st Bureau Group Sixth Engineering Co., LTD., Lanzhou, 730070, PR China

Abstract
Under the effect of load and seasonal rainfall, the disintegrated carbonaceous mudstone (DCM) softens and further disintegrates, causing large settlements and even collapses of the DCM embankments. For this reason, some treatments should be taken to improve the engineering performance of the DCM. In this study, four materials including sodium alginate (SA), calcium chloride (CaCl2), bentonite and nano-Al2O3 were jointly used as modifiers to treat the DCM. The influences of each modifier component on the unconfined compressive strength (UCS), cohesion, angle of internal friction, and coefficient of permeability of the DCM were examined by unconfined compression tests, direct shear tests and permeability tests. The results demonstrated that with the addition of modifiers, the UCS, cohesion and angle of internal friction of the DCM are enhanced, whereas the coefficient of permeability is reduced. The sensitivity analysis showed that the dosage of SA is the dominating factor affecting the engineering performance of the DCM. Thus, special attention should be paid to the dosage of SA when improving the DCM. On the other hand, bentonite is the least important factor for most of the examined engineering properties among the four modifier components. An UCS value that is greater than 1500 kPa was selected as the evaluation criterion, and the stress-strain relationship and failure mode of each sample under unconfined compression were examined. On this basis, eight groups of satisfactory mixing ratios were obtained for the modification of the DCM. It is suggested that when designing mixing ratios of modifiers for the DCM, the recommended SA/DCM ratio is 4%-6%, but the quantities of CaCl2, bentonite and nano-Al2O3 can be adjusted according to the needs and costs.

Key Words
embankment; ground improvement; laboratory analysis; optimization; rock fills; shear strength

Address
Ling Zeng and Huan-Yi Zha: School of Civil Engineering, Changsha University of Science & Technology, 960, Section 2, Wanjiali South Road, Changsha 410114, Hunan, China

Qian-Feng Gao: School of Traffic & Transportation Engineering, Changsha University of Science & Technology,
960, Section 2, Wanjiali South Road, Changsha 410114, Hunan, China

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