scholarly journals Compound Karst Cave Treatment and Waterproofing Strategy for EPB Shield Tunnelling in Karst Areas: A Case Study

2021 ◽  
Vol 9 ◽  
Author(s):  
Yongshui Kang ◽  
Zhi Geng ◽  
Linhai Lu ◽  
Lei Chen ◽  
Xuewei Liu ◽  
...  
Keyword(s):  
Water Inrush ◽  
Earth Pressure ◽  
Karst Area ◽  
Karst Cave ◽  
Karst Caves ◽  
Ground Collapse ◽  
Karst Areas ◽  
Shield Tunnelling ◽  
Epb Shield

There is high risk of water inrush and ground collapse accidents when tunnelling in karst areas. Based on the case study of an urban metro tunnel, this paper focuses on karst cave treatment and waterproofing strategies for earth pressure balancing (EPB) shield tunnelling in karst areas containing large amounts of karst caves and fissures. When the shield machine enters the karst area, water gush easily occurs, posing serious threats to tunnelling safety. The distribution characteristic of limestone fractures, karst caves, and fissures in the karst area were analyzed according to the geological survey results. Further, water inrush risk and engineering difficulties were analyzed. Subsequently, a compound karst cave treatment and waterproofing strategy for EPB shield tunnelling was proposed and implemented. Water inflow is successfully reduced and ground collapse accident is avoided using the compound karst cave treatment and waterproofing strategy.

Study of the Effects of Karst Area Beneath the Tunnel on the Stability of Surrounding Rock

2014 ◽  
Vol 711 ◽  
pp. 402-405
Author(s):  
Li Wei Dong ◽  
Ping Cao ◽  
Jie Liu
Keyword(s):  
Large Scale ◽  
Surrounding Rock ◽  
Vertical Stress ◽  
Karst Area ◽  
Karst Cave ◽  
Karst Caves ◽  
Tunnel Floor ◽  
Stability Of Surrounding Rock ◽  
Karst Areas ◽  
The Stability

Geotechnical engineering in large scale is endangered by the karst areas which are close to the engineering. The stability of the tunnels is greatly affected by the sizes and locations of the karst caves. Based on a engineering example, a study of the effects of karst area beneath the tunnel on the stability of surrounding rock is conducted. It can be concluded that the displacement release of surrounding rocks and the distribution of the vertical stress in surrounding rocks are greatly affected by the sizes of the karst caves and the distance between the tunnel floor and the karst cave.

scholarly journals Characteristics of Karst Cave Development in Urban Karst Area and Its Effect on the Stability of Subway Tunnel Construction

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Fei Xue ◽  
Minjun Cai ◽  
Tianzuo Wang ◽  
Tongyang Zhao
Keyword(s):  
Numerical Models ◽  
Karst Area ◽  
Risk Level ◽  
Tunnel Construction ◽  
Karst Cave ◽  
Subway Tunnel ◽  
Karst Caves ◽  
Metro Tunnel ◽  
The Stability

The existence of karst caves poses a large threat to safe tunnel construction in a karst area. This paper presents a synthetic method to evaluate the collapse risk before subway tunnel construction with Yang-Jian interval tunnel as a case study. The crosshole seismic Computed Tomography (CT) integrated with Geological Drilling (Geo-D) was first applied to accurately delineate the karst location and its scale. Then, 483 groups of seismic wave CT images were recorded, and 524 karst cave anomalies were found. The height of karst caves in the study area is 1–20 m and mainly concentrated at approximately 5 m. The vertical distance between the karst cave and the tunnel is mainly within 15 m. According to the detection results, a series of numerical models were built and calculated using FLAC3D to investigate the effect of different sizes and locations of karst caves on the displacement and stability of the surrounding rock in tunnels. Afterwards, based on the simulation results, the disturbance degree evaluation index was established to quantitatively evaluate the risk level of karst caves. The evaluation results indicate that the buried depth of the karst cave greatly affects the disturbance degree. No treatment is required for the deeply buried karst cave that is more than 7 m from the tunnel. When the distance between the cave and the tunnel is less than 7 m, there is a critical size of the cave. Karst caves that are larger than that critical value must be filled with a single slurry or binary slurry before tunnel construction to eliminate the risk of tunnel collapse. This study can be used to provide a more efficient and economical program for metro tunnel construction above a karst cave.

scholarly journals Influence of Karst Caves at Pile Side on the Bearing Capacity of Super-Long Pile Foundation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Peisen Wang ◽  
Hongyan Ding ◽  
Puyang Zhang
Keyword(s):  
Bearing Capacity ◽  
Pile Foundation ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Horizontal Load ◽  
Karst Cave ◽  
Karst Caves ◽  
Karst Areas ◽  
Vertical Bearing ◽  
Vertical Bearing Capacity

The differences in development and situation of karst caves lead to two kinds of karst caves, and the karst cave may be on the pile side or at the pile bottom, which has a different influence on the bearing capacity of pile foundation. The paper presents a numerical analysis of the influence of karst caves at pile side on the bearing capacity of super-long pile foundation in karst areas. According to the size of pile foundation of a real bridge project, this paper modelized karst caves and investigated the karst cave from the effect of length, height, and thickness of roof on horizontal and vertical bearing capacity of pile foundation. The main conclusions can be drawn as: when the horizontal displacement at the top of pile foundation is greater than 0.05 m, the horizontal load is correlated positively with the length of karst cave; when the vertical displacement is greater than 0.07 m, the vertical load is correlated negatively with the thickness of the roof of karst cave. However, the height of karst cave has little effect on the bearing capacity; also the existence of karst cave has little influence on the dynamic response of pile foundation. The results of this study can be important with reference to the design and construction of pile foundations in karst areas.

scholarly journals Deformation Characteristics of Existing Twin Tunnels Induced by Double Shield Undercrossing with Prereinforcement: A Case Study in Hangzhou

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinjiang Wei ◽  
Mobao Zhang ◽  
Shaojun Ma ◽  
Chang Xia ◽  
Xingwang Liu ◽  
...  
Keyword(s):  
Soft Soil ◽  
Earth Pressure ◽  
Plain Concrete ◽  
Horizontal Displacement ◽  
Shield Tunnel ◽  
Deformation Characteristics ◽  
Pressure Balance ◽  
Concrete Wall ◽  
Shield Tunnelling ◽  
Epb Shield

This paper is based on the case of the earth pressure balance (EPB) shield tunnelling project of the new Metro Line 2 undercrossing the existing Metro Line 1 in the soft soil urban area of Hangzhou. Because the EPB shield must break through a plain concrete wall before undercrossing the existing tunnels, the pipe roof prereinforcement was adopted to stabilize the soil between the existing tunnels and the new shield tunnel. The deformation characteristics of the existing tunnels in the process of double shield undercrossing were discussed. According to the variation of shield position, the settlement development could be divided into three stages: shield approaching subsidence, shield crossing heave, and shield leaving subsidence. The horizontal displacement shows a back and forth variation characteristic consistent with the direction of shield tunnelling. At the junction of tunnel and station, the shield undercrossing caused considerable differential settlement between the existing tunnel and the station. The construction of pipe roof prereinforcement will lead to the presettlement of the existing tunnels. The settlement of the existing tunnels caused by the attitude deviation of pipe roof and grouting disturbance should be reduced in reasonable ranges. In addition, the maximum longitudinal settlement of the existing tunnel during the shield second undercrossing was also discussed. It was considered that the influence of wall breaking is greater than the sequence of shield undercrossing. The driving parameters of shield tunnelling should be optimized before the second crossing.

scholarly journals Optimized Adaptive Neuro-Fuzzy Inference System Using Metaheuristic Algorithms: Application of Shield Tunnelling Ground Surface Settlement Prediction

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinni Liu ◽  
Sadaam Hadee Hussein ◽  
Kamarul Hawari Ghazali ◽  
Tran Minh Tung ◽  
Zaher Mundher Yaseen
Keyword(s):  
Fuzzy Inference System ◽  
Fuzzy Inference ◽  
Earth Pressure ◽  
Ground Settlement ◽  
Pressure Balance ◽  
Inference System ◽  
Neuro Fuzzy ◽  
Shield Tunnelling ◽  
Earth Pressure Balance ◽  
Epb Shield

Deformation of ground during tunnelling projects is one of the complex issues that is required to be monitored carefully to avoid the unexpected damages and human losses. Accurate prediction of ground settlement (GS) is a crucial concern for tunnelling problems, and the adequate predictive model can be a vital tool for tunnel designers to simulate the ground settlement accurately. This study proposes relatively new hybrid artificial intelligence (AI) models to predict the ground settlement of earth pressure balance (EPB) shield tunnelling in the Bangkok MRTA project. The predictive models were various nature-inspired frameworks, such as differential evolution (DE), particle swarm optimization (PSO), genetic algorithm (GA), and ant colony optimizer (ACO) to tune the adaptive neuro-fuzzy inference system (ANFIS). To obtain the accurate and reliable results, the modeling procedure is established based on four different dataset scenarios including (i) preprocessed and normalized (PPN), (ii) preprocessed and nonnormalized (PPNN), (iii) non-preprocessed and normalized (NPN), and (iv) non-preprocessed and nonnormalized (NPNN) datasets. Results indicated that PPN dataset scenario significantly affected the prediction models in terms of their perdition accuracy. Among all the developed hybrid models, ANOFS-PSO model achieved the best predictability performance. In quantitative terms, PPN-ANFIS-PSO model attained the least root mean square error value (RMSE) of 7.98 and a correlation coefficient value (CC) of 0.83. Overall, the attained results confirmed the superiority of the explored hybrid AI models as robust predictive model for ground settlement of earth pressure balance (EPB) shield tunnelling.

Investigation of a large ground collapse, water inrush and mud outburst, and countermeasures during subway excavation in Qingdao: A case study

2021 ◽  
Vol 117 ◽  
pp. 104127
Author(s):  
Feiyue Yan ◽  
Wenge Qiu ◽  
Keguo Sun ◽  
Shuhua Jiang ◽  
Haiyun Huang ◽  
...  
Keyword(s):  
Water Inrush ◽  
Ground Collapse

scholarly journals Hydromechanical Simulation of Tunnel Excavation in Rock Considering a Nearby Karst Cave

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Huiling Zhao ◽  
Fan Zhang ◽  
Xupeng Yao
Keyword(s):  
Surrounding Rock ◽  
Tunnel Lining ◽  
Karst Cave ◽  
Tunnel Engineering ◽  
Tunnel Excavation ◽  
Safety Issues ◽  
Karst Caves ◽  
Karst Areas ◽  
Rock Tunnel ◽  
Design And Construction

Tunnel excavation tends to be affected by karst cavities in karst areas. Some cavities that are at low risk of causing safety issues without treatment tend to be ignored in the design and construction of tunnels to reduce costs. It is necessary to gain a better understanding of the effect of such a cavity on the seepage around a tunnel, the deformation of the surrounding rock, and the stress of the tunnel lining. In this paper, a two-dimensional rock-tunnel hydromechanical model with a karst cave was established with FLAC3D finite difference software to simulate the tunnel excavation with the consideration of seepage. Numerical simulations were performed to analyze the deformation of the surrounding rock, the seepage field of the surrounding rock, and the stress of the tunnel lining, and the results were compared for scenarios when the karst cave is at different locations relative to the tunnel. These results can provide a reference for the design and construction of tunnel engineering in rock with karst caves.

scholarly journals 2D numerical analysis of the seismic response of a karst rock mass: importance of underground caves and geostructural details

2020 ◽  
Vol 42 (1) ◽  
pp. 61-73
Author(s):  
Bruno Giovanni ◽  
Carucci Fabrizio
Keyword(s):  
Rock Mass ◽  
Seismic Response ◽  
Distinct Element ◽  
Seismic Energy ◽  
Karst Cave ◽  
Karst Caves ◽  
Local Seismic Response ◽  
Distinct Element Code ◽  
Static Conditions

AbstractThe present study shows the results of a 2D local seismic response (LSR) analysis, simulated for a geomechanical model consisting of a layered carbonate rock mass with hypogean karst caves and a structural–lithostratigraphic complex setting, in an area within the Municipality of Turi (Apulia, Italy). In this case study a Distinct Element Code (DEM) code (UDEC) was used for the LSR simulations conducted on a model both in the absence and in the presence of two overlapping karst caves. The preliminary stress–strain model analysis show some tensile yielding points clustered on the roof of the upper karst cave, already in static conditions, and the phenomenon becomes even more noticeable in dynamic conditions. This is perfectly in agreement with the real occurrence of a sinkhole that brought to the light the underlying karst cave, in the case study area, in the recent past.The amplification/deamplification factor (FA) was calculated as the ratio of the top value to the bottom value in the model, both of the max X-acceleration and of the spectral Fourier amplitude in three different ranges of frequencies, in order to estimate the effects of LSR on the X-component of the seismic input. According to the previous studies, the results obtained show a generalised deamplification of the seismic ground motion at the top of the model, both without and with underground karst caves, caused by the presence of the upper karst cave and by the seismic energy absorption because of layers’ discontinuity.

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