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CONTENTS
Volume 37, Number 2, April25 2024
 

Abstract
The accurate prediction of grouting upward diffusion height is crucial for estimating the bearing capacity of tip-grouted piles. Borehole construction during the installation of bored piles induces soil unloading, resulting in both radial stress loss in the surrounding soil and an impact on grouting fluid diffusion. In this study, a modified model is developed for predicting grout diffusion height. This model incorporates the classical rheological equation of power-law cement grout and the cavity reverse expansion model to account for different degrees of unloading. A series of single-pile tip grouting and static load tests are conducted with varying initial grouting pressures. The test results demonstrate a significant effect of vertical grout diffusion on improving pile lateral friction resistance and bearing capacity. Increasing the grouting pressure leads to an increase in the vertical height of the grout. A comparison between the predicted values using the proposed model and the actual measured results reveals a model error ranging from -12.3% to 8.0%. Parametric analysis shows that grout diffusion height increases with an increase in the degree of unloading, with a more pronounced effect observed at higher grouting pressures. Two case studies are presented to verify the applicability of the proposed model. Field measurements of grout diffusion height correspond to unloading ratios of 0.68 and 0.71, respectively, as predicted by the model. Neglecting the unloading effect would result in a conservative estimate.

Key Words
bored piles; cavity reverse expansion; grouting diffusion; grouting pressure; post-grouting; soil unloading

Address
Jiaqi Zhang: Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
Chunfeng Zhao and Cheng Zhao: Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
Yue Wu: School of Civil Engineering, Chongqing Jiaotong University, 66 Xuefu Road, Chongqing 400074, China
Xin Gong: Institute of Civil Engineering, Jinggangshan University, Ji'an, Jiangxi 343009, China

Abstract
Standard triaxial cells are commonly used to measure the mechanical behavior of saturated soils. However, this type of standard system is difficult to use for unsaturated soil specimens since it cannot measure the changes in the pore-air volume and pressure. This paper proposes to extend the measurement possibilities of the standard triaxial testing device in a simple way and to adapt it to partially saturated soils. The system is supplied by two hygrometers installed at each end of the cylindrical unsaturated specimen to measure local relative humidity, which allows the derivation of suction. The volumetric strain of the specimen is calculated by analyzing digital photos captured from the outside of the transparent cell wall. Specimens made of kaolin clay, having different hydraulic properties, were tested to verify the reliability of the measurements, and thus, the relevance of the proposed techniques to study the mechanical behavior of unsaturated soils.

Key Words
hygrometer; suction; triaxial test; unsaturated soil; volume change

Address
Qian-Feng Gao: School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China;
Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux, Universite de Lorraine – CNRS UMR 7239,
Arts et Metiers ParisTech, Metz, France
Mohamad Jrad and Mahdia Hattab: Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux, Universite de Lorraine – CNRS UMR 7239, Arts et Metiers ParisTech, Metz, France
Said Taïbi: Laboratoire LOMC, Université Le Havre Normandie & CNRS, Le Havre, France
Jean M. Fleureau: Laboratoire de Mécanique de Paris-Saclay, Universite Paris-Saclay, CentraleSupelec, ENS Paris-Saclay,
CNRS UMR 9026, 3 Rue Joliot Curie, 91190 Gif-sur-Yvette, France

Abstract
This study investigates the effects of loading frequency (f) and specimen size on the liquefaction resistance of clean sand. A series of cyclic direct simple shear tests were conducted on Jumunjin sand with varying consolidated relative densities (40% and 80%), f values (0.05, 0.10, and 0.20 Hz), and diameter to height (D/H) ratios (3.63, 3.18, 2.82, and 2.54). The results demonstrated the significant influence of f and D/H ratio on the number of cycles to liquefaction (Ncyc-liq) and the cyclic resistance ratio (CRR15). It was observed that increasing f linearly increased Ncyc-liq. Increasing the specimen height also led to higher Ncyc-liq values irrespective of the f or relative density. Moreover, a positive correlation between CRR15 and f indicated that higher f yielded higher CRR15. This relationship was more pronounced in dense sand than in loose sand. Specimen height also significantly affected CRR15, with increasing the specimen height resulting in higher CRR15 values. Furthermore, the effect of f on CRR15 was less significant compared to the influence of specimen height. The effect of f on the normalized cyclic resistance ratio (NCRR) was relatively negligible for loose sand but more substantial for dense sand depending on the D/H ratio. Data analysis revealed that the NCRR generally decreases as the D/H ratio increases. An interpolation formula was provided to calculate the NCRR based on the D/H ratio regardless of the f and relative density.

Key Words
liquefaction resistance of sand; loading frequency; specimen height; specimen size ratio

Address
Sung-Sik Park and Dong-Kiem-Lam Tran: Department of Civil Engineering, Kyungpook National University, 80, Daehak-ro Buk-gu, Daegu 41566, Republic of Korea
Dong-Eun Lee: Department of Architectural Engineering, Kyungpook National University, 80, Daehak-ro Buk-gu, Daegu 41566, Republic of Korea

Abstract
A GIS-based landslide susceptibility mapping (LSM) was carried out using frequency ratio (FR), modified frequency ratio (M-FR), analytic hierarchy process (AHP), and modified analytic hierarchy process (M-AHP) methods to identify and delineate the potential failure zones along the Halong – Vandon expressway. The thematic layers of various landslide causative factors were generated for modeling in GIS, including geology, rainfall, distance to fault, distance to road, slope, aspect, landuse, density of landslide, vertical relief, and horizontal relief. In addition, a landslide inventory along the road network was prepared using data provided by the management department during the course of construction and operation from 2017 to 2019, when many landslides were documented. The validation results showed that the M-FR method had the highest AUC value (AUC = 0.971), which was followed by the FR method with AUC = 0.961. The AUC values were 0.939 and 0.892 for the M-AHP and AHP methods, respectively. The generated LSM obtained from M-FR method classified the study area into five susceptibility classes: very low (0), low (0-1), moderate (1-2), high (2-3), and very high (3-4) classes, which could be useful for various stakeholders like planners, engineers, designers, and local public for future construction and maintenance in the study area.

Key Words
Halong Vandon expressway; landslide susceptibility map (LSM); modified analytic hierarchy process method; modified frequency ratio method

Address
Nguyen-Vu Luat: Gia Dinh University, 371 Nguyen Kiem, Go Vap, Hochiminh City 71400, Vietnam
Tuan-Nghia Do: Faculty of Civil Engineering, Thuyloi University, Hanoi, Vietnam
Lan Chau Nguyen: Faculty of Civil Engineering, University of Transportation and Communications, Hanoi, Vietnam
Nguyen Trung Kien: Institute of Geological Sciences-Vietnam Academy of Science and Technology, No.84 Chualang, Dongda, Hanoi, Vietnam

Abstract
The acoustic emission (AE) technique is utilized to estimate the rock failure status in underground spaces. Understanding the AE characteristics under loading conditions is essential to ensure the reliability of AE monitoring. The AE characteristics depend on the material properties (p-wave velocity, density, UCS, and Young's modulus) and damage stages (stress ratio) of the target rock mass. In this study, two groups of granite specimens (based on the p-wave velocity regime) were prepared to explore the effect of material properties on AE characteristics. Uniaxial compressive loading tests with an AE measurement system were performed to investigate the effect of the rock properties using AE indices (count index, energy index, and amplitude index). The test results were analyzed according to three damage stages classified by the stress ratio of the specimens. Count index was determined to be the most suitable AE index for evaluating rock mass stability.

Key Words
acoustic emission; AE index; damage stages; rock properties

Address
Jong-Won Lee: Research Institute of Industrial Technology, Pusan National University, 2 Busandaehak-ro 63beon-gil,
Geumjeong-gu, Busan 46241, Republic of Korea
Tae-Min Oh: Department of Civil and Environmental Engineering, Pusan National University, 2 Busandaehak-ro 63beon-gil,Geumjeong-gu, Busan 46241, Republic of Korea
Hyunwoo Kim: Mineral Exploration and Mining Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM),
124 Gwahang-no, Yuseong-gu, Daejeon 34132, Republic of Korea
Min-Jun Kim: Deep Subsurface Storage & Disposal Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM),
124 Gwahang-no, Yuseong-gu, Daejeon 34132, Republic of Korea
Ki-Il Song: Department of Civil Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212,Republic of Korea

Abstract
The natural frequency shift under cyclic environmental loads is a key issue in the design of monopile-based offshore wind power turbines because of their dynamic sensitivity. Existing evidence reveals that the natural frequency shift of the turbine system in sand is related to the varying foundation stiffness, which is caused by soil deformation around the monopile under cyclic loads. Therefore, it is an urgent need to investigate the effect of soil deformation on the system frequency. In the present paper, three generalized geometric models that can describe soil deformation under two-way cyclic loads are proposed. On this basis, the cycling-induced changes in soil parameters around the monopile are quantified. A theoretical approach considering three-spring foundation stiffness is employed to calculate the natural frequency during cycling. Further, a parametric study is conducted to describe and evaluate the frequency shift characteristics of the system under different conditions of sand relative density, pile slenderness ratio and pile-soil relative stiffness. The results indicate that the frequency shift trends are mainly affected by the pile-soil relative stiffness. Following the relevant conclusions, a design optimization is proposed to avoid resonance of the monopile-based wind turbines during their service life.

Key Words
monopile; natural frequency; shift; soil deformation; two-way cyclic loads

Address
Yang Wang: School of Civil and Architectural Engineering, Shandong University of Technology, Zibo, China
Mingxing Zhu: School of Civil Engineering and Architecture, Jiangsu University of Science and Technology, Zhenjiang, China
Guoliang Dai: School of Civil Engineering, Southeast University, Nanjing, China
Jiang Xu: Institute of Geotechnical Engineering, Yangzhou University, Yangzhou, China
Jinbiao Wu: School of Resource and Safety Engineering, Central South University, Changsha, China

Abstract
In this paper, a unified time-dependent constitutive model of Darcy flow and non-Darcy flow is proposed. The influencing factors of flow velocity are discussed, which demonstrates that permeability coefficient is the most significant factor. Based on this, the dynamic evolution characteristics of water inrush during tunneling through fault fracture zone is analyzed under the constant permeability coefficient condition (CPCC). It indicates that the curves of flow velocity and hydrostatic pressure can be divided into typical three stages: approximate high-velocity zone inside the fault fracture zone, velocity-rising zone near the tunnel excavation face and attenuation-low velocity zone in the tunnel. Furthermore, given the variation of permeability coefficient of the fault fracture zone with depth and time, the dynamic evolution of water flow in the fault fracture zone under the variable permeability coefficient condition (VPCC) is also studied. The results show that the time-related factor (a) affects the dynamic evolution distribution of flow velocity with time, the depth-related factor (A) is the key factor to the dynamic evolution of hydrostatic pressure.

Key Words
constant permeability coefficient condition; dynamic evolution characteristics; fault fractured zone; unified time-dependent constitutive model; variable permeability coefficient condition; water inrush

Address
Jian-hua Wang, Xing Wan, Cong Mou and Jian-wen Ding: Transportation College, Southeast University, Nanjing 210096, China

Abstract
Buried pipelines can be classified as continuous and segmented pipelines. These infrastructures can be damaged either by ground movement or by seismic wave propagation during an earthquake. Permanent ground deformations (PGD) include surface faulting, liquefaction-induced lateral spreading and landslide. Liquefaction is a major problem for both superstructures and infrastructures. Buyukcekmece lake zone, which is the studied region in this paper, is a liquefaction prone area located near the North Anatolian Fault Line. It is an active fault line in Turkey and a major earthquake with a magnitude of around 7.5 is expected in this investigated region in Istanbul. It is planned to be constructed a new 12" steel natural gas pipeline from one side of the lake to the other side. In this study, this case has been examined in terms of two different support conditions. Firstly, it has been defined as a beam in liquefied soil and has built-in supports at both ends. In the other approach, this case has been modeled as a beam in liquefied soil and has vertical elastic pinned supports at both ends. These models have been examined and some solution proposals have been produced according to the obtained results. In this study, based on this sample, it is aimed to determine the behaviors of buried continuous pipelines subject to liquefaction effects in terms of buoyancy.

Key Words
buried continuous pipeline; earthquake; liquefaction; North Anatolian Fault Line; underground construction

Address
Adil Yigit: Istanbul Rumeli University, Civil Engineering Department, Istanbul, Turkiye

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