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Either geological features or some artificial factors, like sewer pipe leakage or incomplete construction work, cause ground sinking in urban areas. This study reports on a recent ground sinking, which occurred on account of complex factors related to geology and artificial excavation work. A cylindrical displacement of 14 m long in the ground, wit...
Citations
... Shanghai Metro [5] A large number of cracks appeared on the ground surface outside the foundation pit, and the settlement of the buildings around the foundation pit and the ground surface exceeded 40 mm High groundwater level; incomplete wall brushing at the joint of the enclosure structure -Korean Metro [6] Two students fell into a 3 m × 3 m sinkhole outside the pit ...
... In terms of research on ground settlement due to pit excavation considering hydraulic factors, researchers are currently focusing on the pit dewatering process, with little consideration given to the combined loss of water and sand [16][17][18]. Thus, the hazards of water and sand loss in foundation pits warrant Shanghai Metro [5] A large number of cracks appeared on the ground surface outside the foundation pit, and the settlement of the buildings around the foundation pit and the ground surface exceeded 40 mm High groundwater level; incomplete wall brushing at the joint of the enclosure structure -Korean Metro [6] Two students fell into a 3 m × 3 m sinkhole outside the pit ...
... Sand particles are quick high pore ratio and permeability, resulting in a substantial amount sand in a short period of time, which causes surface subsidence. Fo excavation of a 38-meter-deep pit in Seoul, South Korea, water and the retaining structure caused the collapse of a 3 m × 3 m sinkhole ou in a substantial loss of life and property safety [6]. This study utilizes to conduct fluid-solid coupling simulation studies, qualitatively nisms of the aforementioned processes. ...
The existence of defects in the enclosure structure is the primary cause of water and sand leakage in foundation pits, as well as being a significant source of danger in pit construction, but current research lacks an in-depth investigation of the generation mechanism and gestation process. In this paper, which comprehensively considers the microscopic particles and macroscopic level, the development mechanism of a water and sand leakage disaster in a foundation pit with a water-rich sand layer was studied using the principle of computational fluid dynamics and discrete element method coupled analysis (CFD–DEM); moreover, based on the anisotropy of the particle force and fluid energy analysis, the deformation of the stratum and ground stress field were analyzed. The results show that the stress field will produce a plugging effect at a certain distance from the defect, and the strata exhibit a dominant displacement tendency in the vertical direction, resulting in the emergence of a gradually concave stress relaxation zone and an elliptical contour in the strata displacement map near the defect. The fluid energy describes the displacement of the sand layer very well, and it is separated into the sand layer’s centralized loss region and the major loss area based on the high and low levels of the fluid energy class. The impact of fluid at the defect reaches the maximum kinetic energy, which penetrates the structural weakness and causes the loss of sand particles, and the cross-section of the water influx near the defect gradually expands with the loss of particles, indicating that there is a danger of further expansion of the defect under the impact of water flow. These results have technical implications for the management of water and sand leakage disasters in foundation pit engineering.
... Subsequently, ground sinking occurs as void spaces become larger. Jo et al. [1] reported that the vibration transmitted by vehicles in metropolitan cities could cause the collapse of enlarged underground void spaces. The conventional method involves compacting well-graded soils around sewage pipes or culvert boxes using mechanical equipment (e.g., a vibrator) to prevent ground sinking. ...
Controlled low-strength materials (CLSMs) have been developed using various byproducts for backfilling or void-filling around pipelines or culvert boxes. However, these CLSMs have encountered issues related to their inadequate placement around underground facilities, despite satisfying the performance requirements, especially flowability, recommended by the American Concrete Institute (ACI) 229 committee. In this study, a new CLSM is developed to ensure a significantly higher flowability, lower segregation, and faster installation compared with previously developed CLSMs. This is achieved through a series of laboratory tests. To enhance the flowability and prevent segregation, a calcium-sulfoaluminate-based binder and fly ash are used in combination with two types of additives. The measured flowability of the new CLSM is 700 mm, while its compressive strength and bleeding satisfy the general criteria specified by the ACI 229R-13. In addition, the performance of the developed CLSM is compared with that of predeveloped CLSMs. The new CLSM was not only shown to exhibit the highest flowability, but also to satisfy the specified requirements for compressive strength and bleeding. Overall, it is anticipated that the developed CLSM can significantly reduce the costs related to the disposal of old pavements, the installation of new pavements, and other construction expenses compared to the costs related to the conventional method, even though the expenses for the backfill materials could increase due to the higher production costs of CLSMs than soil. In addition, there is a need to investigate its field applicability in order to evaluate the precise costs, maintenance, and long-term stabilities after installation.
... Considering this, appropriate remedial measures or countermeasures need to be prepared in advance. Once a through-wall leaking event took place, the following measures are suggested to be adopted timely (Cheng et al., 2020;Feng and Lu, 2016;Jo et al., 2016;Ni and Cheng, 2012;Tan and Lu, 2017): ...
Through-wall leakages took place frequently during those excavations in water-rich sandy strata, which often resulted in engineering failures (e.g., global instability of retaining structures and damages to adjacent existing structures) and even injuries and/or fatalities. In spite of this, only few comprehensive studies relevant to this
topic have been known in literature to date. During the recent construction of Metro Line 1 in the city of Nantong, China, hundreds of through-wall leaking incidents had taken place, which provided an opportunity for comprehensively investigating through-wall leaking in water-rich sandy strata. First, a database comprised of
hundreds of leaking accidents collected in Nantong was built in this study; then, these leaking incidents were classified into three major levels by a descriptive statistics method, i.e., minor seepage without soil loss, massive leakage with a handful of soil loss, and massive through-wall ingress of water and soils. The primary contributory factors of these leaking events included exposure of steel bars of diaphragm wall (DW) panels, local bulging of wall faces, flawed joints of DW panels, and complicated geohydrological conditions. Moreover, the characteristics of these leaking events were examined in terms of their temporal and spatial distributions as well as excavation behaviors. Finally, some practical measures and solutions to deal with potential through-wall leaking incidents during excavations in water-rich sandy strata were proposed.
... However, severe water leakage still occurs through the wall joints under high water pressure in the water-rich ground. Especially when poor quality emerges, calamities such as ground settlement and collapse occur, as reported in places like Taipei (Hwang et al. 2016), Boston (Poletto & Tamaro 2011), Hangzhou (Wu et al. 2015), Nanchang (Feng & Lu 2016), Seoul ( Jo et al. 2016), Shanghai (Tan & Lu 2017) etc. ...
Attributed to the opacity of soil and rock mass, seepage visualization is a thorny problem in the model test around diaphragm wall leakage, which has played an increasingly significant role in deep excavation engineering recently. Enlightened by the geoelectrical field response method, the electrical potential method was proposed in this study. By means of a model experiment, the applicability of the proposed method was verified and approaches for evaluating the seepage characteristics were discussed. Based on the analyses, several conclusions could be drawn: (i) based on the electrical potential method, a circuit is established by connecting the power supplier, the ground and several monitoring electrodes and voltmeters. When the seepage passes through a certain electrode, the increase of voltage can be observed so that the seepage flow can be visualized. (ii) The effectiveness of the electrical potential method is validated by the excellent agreement between photos of practical seepage flow and the nephograms depicted on the basis of the voltages measured on the electrodes. (iii) The time history curve of the measured voltage is S-shaped and composed of a small ladder rising stage, a sharp increasing stage and a convergence stage. The seepage flow velocity, inhomogeneity and the leakage point location can be evaluated by the time cost between the two major rise beginning points, the time cost for the major rise process and the maximum measured voltage, respectively. The proposed method can provide valuable support to the diaphragm wall leakage model test and other seepage experiments.
... Around 85% of all ground subsidence cases in South Korea are caused by sewer pipe defects (Karoui et al. 2018). According to Jo et al. (2016), a total of 53 pipe defect-related sinkhole accidents were reported in South Korea between 2012 and 2014. In Japan, there are 3,000-4,000 sinkhole accidents reported annually (Khudhair et al. 2020). ...
Underground water main leakage is one of the main causes of instability of soils and sinkholes. In the event of a water main burst, the pressure is upward and hence the soil layer should be analyzed for blowout stability. Conversely, leakage from low-pressure utilities such as sewer pipes would erode the surrounding soil media and leave it unstable with an internal opening created. In such a situation, the possible failure scenario would be in collapse stability. This study set out to quantify the collapse stability performance of three idealized cavity shapes above the damaged pipe. Advanced numerical limit analysis was used to obtain upper and lower bound solutions of the problem. The study provides useful engineering information in the form of design charts and tables for a wide range of design parameters, which can greatly assist in decision making by practical engineers.
... Tan et al. [19] analyzed the causes of seepage during deep foundation pit excavation in Shanghai subway and studied the change law of vertical and horizontal surface displacement of the enclosure wall caused by water and sand leakage. Jo et al. [20] investigated the development law of ground subsidence caused by seepage during deep foundation pit excavation through on-site investigation. Koltuk et al. [21,22] analyzed the seepage and deformation of the deep foundation excavation precipitation process through numerical simulation and studied the deformation law of foundation pit construction under the action of seepage. ...
The leakage of an enclosure structure will cause abnormal changes in the seepage flow field, which in turn can lead to the deformation of the enclosure structure and affect the surrounding geotechnical body. In this paper, a fiber-optic temperature measurement system is used to detect the location of the seepage points in a station of the Qingdao subway during open pit excavation, and the abnormal variation of the seepage field caused by the seepage points is obtained by numerical calculation and field measurement. Then, numerical simulation is performed to analyze the effects of seepage field anomalies on the deformation of the enclosure structure and surface settlement. It is found that the seepage flow caused by the leakage point has a significant influence on the surface settlement and the deformation of the enclosure structure. With the increase of excavation depth, the deformation of the enclosure structure increases and the maximum deformation position shifts downward. The deformation of the enclosure structure decreases when the leakage point exists. The surface volume also increases gradually with the excavation, and the maximum surface settlement position shifts outward significantly. The settlement range becomes larger when the leakage point exists.
... A survey conducted in Seoul, South Korea, demonstrated that the leading causes of underground soil erosion are defective sewer and water pipes and excavation activities (Indiketiya, Jegatheesan & Rajeev, 2017). However, a more significant percentage of this underground subsidence in Seoul is caused by defective sewer pipes than excavation works, representing 85% and 14%, respectively (Jo, Cho % Jang, 2016). For example, on a construction site at Yongsan Station, Seoul, South Korea, a sudden ground sinking caused by loss of soil particles and groundwater leakage from a defect in an excavation wall caused two pedestrians to fall into the sinkhole (Jo, Cho % Jang, 2016). ...
... However, a more significant percentage of this underground subsidence in Seoul is caused by defective sewer pipes than excavation works, representing 85% and 14%, respectively (Jo, Cho % Jang, 2016). For example, on a construction site at Yongsan Station, Seoul, South Korea, a sudden ground sinking caused by loss of soil particles and groundwater leakage from a defect in an excavation wall caused two pedestrians to fall into the sinkhole (Jo, Cho % Jang, 2016). Therefore, this research was prudent to obtain information vital to preventing such a disaster that threatens public safety. ...
Cases of road cave-ins have been reportedly increasing globally and reports have associated this phenomenon to underground soil erosion due to defective sewer pipes. As the sewer pipes age, they may develop some defects which may lead to cracks and crevices that will lead to infiltration of the soils surrounding the pipe into the pipe, leading to the formation of cavities around the pipe. Therefore, this study investigated the factors behind the causes of underground soil erosion due to defective sewer pipes and proffered solutions for combating underground soil erosion due to defective sewer pipes. The study objective included; (a) establishing how the soil particle sizes affect the internal soil erosion due to defective sewer pipes, (b) determination of the effect of defect sizes on the internal soil erosion due to defective sewer pipes, (c) establishing the effect of the embedment material used on the internal soil erosion due to defective sewer pipes, (d) investigation of the type of soil erosion mechanism in the presence of a buried sewer pipe defect caused by the groundwater infiltration process. The methodology of the study involved reviewing and analyzing secondary qualitative and quantitative data. The findings established that the defect size of the pipe, the type and characteristics of the soil and the type of embedment materials used affected erosion of soil around a defective sewer pipe.
... Furthermore, soil particles near the damaged pipe flow into the pipe, thereby loosening the surrounding subgrade and inducing a cavity. Cavities beneath the plate structure are difficult to detect with the naked eye [2], and they may lead to rapid failure, which may in turn result in significant damages [3]. ...
The objective of this study is to detect a cavity and estimate its size using sound waves in a laboratory model chamber filled with dry sand. One side of the chamber is covered with an acrylic plate, and a cavity is placed between the plate and sand. Sound waves are generated by impacting the plate with an instrumented hammer, and are measured using a microphone. The measured sound waves are analyzed with four comprehensive analyses including the measured area under the rectified signal envelope (MARSE) energy, flexibility, peak magnitude of wavelet transform, and frequency corresponding to the peak magnitude. The test results show that the accuracy of cavity detection using the MARSE energy is higher for thicker plates, whereas that using flexibility is higher for thinner plates. The accuracies of cavity detection using the peak magnitude of wavelet transform, and frequency corresponding to the peak magnitude are consistently high regardless of the plate thickness. Moreover, the cavity size may be under- or overestimated depending on the plate thickness and the selected analysis method. The average of the cavity sizes estimated by these methods, however, is slightly larger than the actual cavity size regardless of the plate thickness. This study demonstrates that microphones may be effectively used for the identification of a cavity and the estimation of its size.
... . 슬러리 월 공사의 굴착 과정 시 벽체 내외부 간의 수두 차이로 인한 지하수 흐름이 발생할 수 있으며, 이로 인하여 흙 입자가 유실되어 지표면에 공동이 발생할 수 있다 (Jo et al., 2016). 또한, 터널 굴착 시 막장 부근의 터널 천장부가 지보재 설치 전 붕괴할 경우, 흙의 유실에 의한 공동이 발생할 수 있다 (Song et al., 2012). ...
... 또한, 파손된 매설관 부근의 흙 입자가 매설관 내부 로 유입되어 주변 지반은 상대적으로 느슨해지거나 공동 이 발생할 수 있다. 이러한 판 구조물 하부의 공동은 구조물 의 파괴 전에는 육안으로 탐지하기 어려우며 (Benedetto and Pensa, 2007), 매설관 파손으로 인하여 공동이 생성된 경우 구조물의 파괴는 급격하게 발생하므로 큰 피해를 야기할 수 있다 (Jo et al., 2016). ...
Failure of plate structures such as pavements can be caused by the occurrence of cavities beneath the structure. In this study, a cavity beneath the plate structure were detected in a laboratory model chamber using a hammer and microphone. Specifically, a chamber was constructed using an acrylic plate and dry soil to simulate the pavement and the subgrade, respectively. A plastic box was placed between the acrylic plate and dry soil to simulate a cavity beneath the pavement. The sound waves generated by impacting the acrylic plate with a hammer were measured using a microphone. The measured area under the rectified signal envelope (MARSE) energy was calculated for the measured sound waves, and the variation in it were analyzed according to the measurement location. The test results show that the signal attenuation was low at the cavity section owing to the conservation of impact energy and that the signal amplitude becomes lower at the soil section owing to the weakened flexural vibration. Therefore, the estimated MARSE energy at the cavity section was larger than that at the soil section. This study demonstrates the effective utilization of microphones for detecting cavities beneath the plate structures.
... Land subsidence is a threat faced by big cities with extensive development that can negatively impact the environment, social systems, and the economy [1]. Subsidence occurs due to geological causes or anthropogenic processes such as massive urban development, infrastructure development [2,3], tunneling [4][5][6], water extraction [7][8][9], and earthquakes [10]. Subsidence has been observed in several metropolitan cities, including Mexico City [11], Shanghai [12], and Jakarta [13][14][15]. ...
The aims of this research were to map and analyze the risk of land subsidence in the Seoul Metropolitan Area, South Korea using satellite interferometric synthetic aperture radar (InSAR) time-series data, and three ensemble machine-learning models, Bagging, LogitBoost, and Multiclass Classifier. Of the types of infrastructure present in the Seoul Metropolitan Area, subway lines may be vulnerable to land subsidence. In this study, we analyzed Persistent Scatterer InSAR time-series data using the Stanford Method for Persistent Scatterers (StaMPS) algorithm to generate a deformation time-series map. Subsidence occurred at four locations, with a deformation rate that ranged from 6-12 mm/year. Subsidence inventory maps were prepared using deformation time-series data from Sentinel-1. Additionally, 10 potential subsidence-related factors were selected and subjected to Geographic Information System analysis. The relationship between each factor and subsidence occurrence was analyzed by using the frequency ratio. Land subsidence susceptibility maps were generated using Bagging, Multiclass Classifier, and LogitBoost models, and map validation was carried out using the area under the curve (AUC) method. Of the three models, Bagging produced the largest AUC (0.883), with LogitBoost and Multiclass Classifier producing AUCs of 0.871 and 0.856, respectively.
