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CONTENTS
Volume 30, Number 4, August25 2022
 


Abstract
This paper analyzes the ground surface settlements induced by side-by-side twin shield tunnels bored in sedimentary soils, which primarily consist of sand with clay strata above the tunnel crown. The measurements were obtained during the construction of twin tunnels underneath the Incheon International Airport (IIA) located in Korea. The measured surface settlement troughs are approximated with Gaussian functions. The trough width parameters i and K of the settlement troughs produced by the first and second tunnel passings are determined, along with those for the total settlement trough. The surface settlement troughs produced by the first shield passing are reasonably represented by a symmetric Gaussian curve. The surface settlement troughs induced by the second shield tunnel display marginal asymmetric shapes at selected sections. The total settlement troughs are fitted both with a shifted symmetric Gaussian function and the superposition method utilizing an asymmetric function for the incremental trough produced by the second tunnel. It is revealed that the superposition method does not always produce better fits with the total settlement. Instead, the shifted symmetric Gaussian function is overall demonstrated to provide more favorable agreements with the recordings. Therefore, the shifted symmetric Gaussian function is recommended to be used in the design for the prediction of the settlement in clays caused by twin tunneling considering the simplicity of the procedure compared with the superposition method. The amount of increase in the width parameter K for the twin tunnel relative to that for the single tunnel is quantified, which can be used for a preliminary estimate of the surface settlement in clay induced by twin shield tunnels.

Key Words
asymmetrical function; shifted Gaussian curve; surface settlement trough; trough width parameter; twin shield tunnel

Address
Chang-Yoon Ahn: Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Sageun-dong, Seongdong-gu, Seoul, Korea; HDC Hyundai Development Company, 55, Hangang-daero 23-gil, Yongsan-gu, Seoul, Korea
Duhee Park: Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Sageun-dong, Seongdong-gu, Seoul, Korea
Sung-Woo Moon: Department of Civil and Environmental Engineering, Nazarbayev University, 53 Kabanbay Batyr Ave, Nur-Sultan 010000, Kazakhstan

Abstract
The electrical resistivity method is a well-known geophysical method for observing underground conditions, (such as anomalies) and the properties of soil and rock (such as porosity, saturation, and pore fluid characteristics). The shape of electrodes used in an electrical resistivity survey depends on the purpose of the survey and installation conditions. Most electrodes for field applications are cylindrical for sufficient contact with the ground, while some are conically sharpened at their tips for convenient penetration. Previous study only derived theoretical equations for rod-shaped electrodes with spherical tips. In this study, the theoretical resistance for two cylindrical electrodes with conical tips is derived and verified experimentally. The influence of the penetration depth and tip on the measurement is also discussed.

Key Words
cylindrical electrode; electrical resistance; electrode tip; penetration depth

Address
Chang-Ho Hong, Jin-Seop Kim: Disposal Performance Demonstration Research Division, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989, Yuseong-gu, Daejeon, 34057, Republic of Korea
Song-Hun Chong: Department of Civil Engineering, Sunchon National University, 255 Jungang-ro, Sunchon, 57922, Republic of Korea

Abstract
When rock burst occurs, the damaged coal, rock and other fragments can be ejected to the roadway at a speed of up to 10 m/s. It is extremely harmful to personnel and mining equipment, and seriously affects the mining activities. In order to study the energy evolution characteristics, especially kinetic energy, in the process of rock mass failure, this paper first analyzes the energy changes of the rock in different stages under uniaxial compression. The formula of the kinetic energy of rock sample considering the energy from the indenter of the testing machine is obtained. Then, the uniaxial compression tests with different stiffness ratios of the indenter and rock sample are simulated by numerical simulation. The kinetic energy Ud, elastic strain energy Ue, friction energy Uf, total input energy U and surface energy Uo of crack cracking are analyzed. The results show that: The stiffness ratio has influence on the peak strength, peak strain, Ud, Ue, Uo, Uf and U of rock samples. The variation trends of strength, strain and energy with stiffness are different. And when the stiffness ratio increases to a certain value, if the stiffness of the indenter continues to increase, it will have no longer effect on the rock sample.

Key Words
kinetic energy; rock burst; stiffness; testing machine; uniaxial compression

Address
Yunliang Tan: State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology, Qingdao 266590, China; College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, 266590, China; Shandong Energy Group, Jinan 250014, China
Qing Ma: College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, 266590, China
Cunwen Wang: Shandong Energy Group, Jinan 250014, China
Xuesheng Liu: State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology, Qingdao 266590, China; College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, 266590, China

Abstract
The seismic failure-prone region in Istanbul has been examined in terms of the segmented pipelines. Although some researchers have suggested that this territory should be left as a green land, many people continue to live in this area. This region is about 9-10 km away from the North Anatolian Fault Line. This fault zone is an active right-lateral strike-slip fault line in Turkey and an earthquake with a magnitude of 7.0-7.5 is expected in the Marmara Sea. Therefore, superstructures and infrastructures are under both land sliding risks and seismic risks in this area. Because there are not any pipeline-fault line intersection points in the region, in this study, it has been focused on the behaviors of the segmented (sewage or stormwater) pipelines subject to earthquake-induced permanent ground deformation and seismic wave propagation. Based on the elastic beam theory some necessary analyses have been carried out and obtained results of this approximation have been examined.

Key Words
earthquake; landslide; segmented pipeline; seismic wave propagation; underground construction

Address
Adil Yigit: Istanbul Natural Gas Distribution Company (IGDAS), IGDAS Kavacik Hizmet Binasi, Beykoz, Istanbul, Türkiye

Abstract
One of the most frequent issues in tunnel excavation is the collapse of rock blocks and the dropping of rock fragments from the tunnel face. The tunnel face can be reinforced using a number of techniques. One of the most popular and affordable solutions is the use of face longitudinal dowels, which has benefits including high strength, flexibility, and ease of cutting. In order to examine the reinforced face, this work shows the longitudinal deformation profile and ground response curve for a tunnel face. This approach is based on assumptions made during the analysis phase of problem solving. By knowing the tunnel face response and dowel behavior, the interaction of two elements can be solved. The rock element equation derived from the rock bolt method is combined with the dowel differential equation to solve the reinforced ground response curve (GRC). With a straightforward and accurate analytical equation, the new differential equation produces the reinforced displacement of the tunnel face at each stage of excavation. With simple equations and a less involved computational process, this approach offers quick and accurate solutions. The FLAC3D simulation has been compared with the suggested analytical approach. A logical error is apparent from the discrepancies between the two solutions. Each component of the equation

Key Words
analytical method; convergence confinement method; longitudinal dowels; tunnel face; weak rocks

Address
Nima Rahimpour: Faculty of Engineering, University of Tabriz, Tabriz, Iran
Morteza MohammadAlinejad Omran, Amir Bazrafshan Moghaddam: Department of Civil Engineering, Shahrood University of Technology, Shahrood, Iran

Abstract
Unsaturated soil at high suctions is widespread. Many civil engineering projects are related to the hydro-mechanical behavior of unsaturated soils at high suctions, particularly in arid and semiarid areas. To investigate water retention behaviors of nine clayey soils (one is classified as fat clay and the others are classified as lean clay according to the unified soil classification system), the high suction (3.29-286.7 MPa) was imposed on the specimens at zero net stress by the vapor equilibrium technique. In this paper, the effect of void ratio on the water retention behavior at high suction was discussed in detail. Validation data showed that soil types, i.e., different mineralogical compositions, are critical in the soil water retention behavior at a high suction range. Second, the hysteresis behavior at a high suction range is mainly related to the clay content and the specific surface area. And the mechanism of water retention and hysteresis behavior at high suctions was discussed. Moreover, the maximum suction is not a unique value, and it is crucial to determine the maximum suction value accurately, especially for the shear strength prediction at high suctions. If the soil consists of hydrophilic minerals such as montmorillonite and illite, the maximum suction will be lower than 106 kPa. Finally, using the area of hysteresis to quantify the degree of hysteresis at a high suction range is proposed. There was a good correlation between the area of hydraulic hysteresis and the specific surface area.

Key Words
high suction; hysteresis behavior; soil water retention behavior; unsaturated soil

Address
Ze Li, You Gao: School of Civil and Environmental Engineering, Ningbo University, 818 Fenghua Road, Ningbo 315211, China
Haihao Yu: Laboratory of Geomechnics and Geotechnical Engineering, Guilin University of Technology, 12 Jian Gan Road, Guilin, 541004, China
Bo Chen: College of Civil Engineering and Architecture, Quzhou University, 78 Jiuhua Road, Quzhou 324000, China
Long Wang: School of Environment and Civil Engineering, Jiangnan University, Wuxi, 214122 ,China

Abstract
Although pipelines are composed of segmental tubes commonly connected by rubber gasket or push-in joints, current studies mainly simplified pipelines as continuous structures. Effects of joints on three-dimensional deformation mechanisms of existing pipelines due to tunnel excavation are not fully understood. By conducting three-dimensional numerical analyses, effects of pipeline burial depth, tunnel burial depth, volume loss, pipeline stiffness and joint stiffness on bending strain and joint rotation of existing pipelines are explored. By increasing pipeline burial depth or decreasing tunnel cover depth, tunnelinginduced pipeline deformations are substantially increased. As tunnel volume loss varies from 0.5% to 3%, the maximum bending strains and joint rotation angles of discontinuous pipelines increase by 1.08 and 9.20 times, respectively. By increasing flexural stiffness of pipe segment, a dramatic increase in the maximum joint rotation angles is observed in discontinuous pipelines. Thus, the safety of existing discontinuous pipelines due to tunnel excavation is controlled by joint rotation rather than bending strain. By increasing joint stiffness ratio from 0.0 (i.e., completely flexible joints) to 1.0 (i.e., continuous pipelines), tunneling-induced maximum pipeline settlements decrease by 22.8%-34.7%. If a jointed pipeline is simplified as a continuous structure, tunneling-induced settlement is thus underestimated, but bending strain is grossly overestimated. Thus, joints should be directly simulated in the analysis of tunnel-soil-pipeline interaction.

Key Words
bending strain; joint rotation; pipeline; three-dimensional; tunnel

Address
Jiangwei Shi, Jinpu Wang: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing, Jiangsu 210024, China
Xiaojia Ji: Intelligent Safe Collaborative Innovation Center, Zhejiang College of Security Technology, Wenzhou 325016, China
Huaqiang Liu: Material and Structural Engineering Department of Jiangsu Water Research Institute, Yangzhou 225000, China
Hu Lu: Shenzhen Polytechnic, No. 7098 Liu Xian Avenue, Nanshan District, Shenzhen, China

Abstract
The Segregation Potential (SP) is one of the most widely used predictors of frost heave in cold regions. Laboratory step-freezing tests determining a representative SP at the onset of the formation of the last ice lens (near the thermal steady state condition) can predict susceptibility to frost heave. Previous work has proposed empirical semi-log fitting for determination of the representative SP and applied it to several fine-grained soils, but considering only frost-susceptible soils. The presence of fines in coarse-grained soil affects frost susceptibility. Therefore, it is required to evaluate the applicability of the empirical semilog fitting for both frost-susceptible and non-frost-susceptible soils with fines content. This paper reports laboratory frost heave tests for fines contents of 5%-70%. The frost susceptibility of soil mixtures composed of sand and silt was classified by the representative SP, and the suitability of the empirical semi-log fitting method was assessed. Combining semi-log fitting with simple laboratory frost heave testing using a temperature-controllable cell is shown to be suitable for both frost-susceptible and non-frost-susceptible soils. In addition, initially non-frost-susceptible soil became frost susceptible at a 10%-20% weight fraction of fines. This threshold fines content matched well with transitions in the engineering characteristics of both the unfrozen and frozen soil mixtures.

Key Words
fines content, frost heave, frost susceptibility, segregation potential, semi-log fitting method, simple laboratory frost heave testing

Address
Hyunwoo Jin, Byung Hyun Ryu and Jangguen Lee: Department of Future and Smart Construction Research, KICT, 283, Goyang-daero, Ilsanseo-gu, Goyang-si, Gyeonggi-do, Republic of Korea


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