科创中国

© 2016, Science Press. All right reserved. The transient electromagnetic method is widely used in prediction of water-bearing structures in front of a tunnel face. But its decay curves are easily polluted in the environment with strong interferences, which can cause false abnormal bodies in determination. We take the Tunnel Boring Machine (TBM) as an example to analyze the influence and response characteristics of such a large metal body in tunneling to TEM detection. We obtain the TBM influences on the TEM decay curves. In addition, we establish a method to remove these influences. We use a three-dimensional finite difference time domain modeling algorithm to simulate the complex environment in tunnels. A vertical water-filled fault is designed in front of a tunnel face as the basic model. Models considering different distances between the fault and tunnel face, different resistivity values between the fault and the background, different fault sizes or thicknesses, etc. are calculated and compared with the normal model without the fault and TBM. By analyzing the simulated results, we propose a method to remove the influences from TBM according to superposition principle. The response of TBM is obtained by subtracting an only tunnel model response from a model containing tunnel and TBM responses. We consider this as the TBM influence background. In modeling or potential future field surveys, the TBM influence background can be subtracted from the total decay curves. Then, the TBM influence is removed. We design 8 groups of numerical models to test the efficiency of our method. The method is tested by comparing the decay curves and apparent resistivity between the removed data and the modeling data without TBM inside. By analyzing the modeling results of TBM, we find the following two significant results: (1) The response of TBM in a decay curve is likely a low resistivity target which will of course be a false abnormal body if not corrected in the result. Its influence is mainly in the early time. And (2) the response from the fault is focusing at relatively late time. By this, the responses of the fault and the TBM can be identified for some models with enough size or resistivity differences. We simulate the TEM responses of TBM in tunneling and analyze its characteristics in tunneling. Although the TBM responses pollute the decay curves, the abnormal body responses have different characteristics and can be distinguished from the receiver data. We show a simple method to remove the TBM influences from the total curves by subtracting the simulated responses. The method can be used to remove strong interferences of TEM detection not only in tunneling but also in other application environments including ground, airborne, semi-airborne and marine TEM.

Sun Huai-Feng;Li Shu-Cai;Li Xiu;Lu Xu-Shan;Ren Bao-Hong

Acta Geophysica Sinica

2016

© 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Detecting, real-time monitoring and early warning of underground water-bearing structures are critically important issues in prevention and mitigation of water inrush hazards in underground engineering. Direct current (DC) resistivity method is a widely used method for routine detection, advanced detection and real-time monitoring of water-bearing structures, due to its high sensitivity to groundwater. In this study, the DC resistivity method applied to underground engineering is reviewed and discussed, including the observation mode, multiple inversions, and real-time monitoring. It is shown that a priori information constrained inversion is desirable to reduce the non-uniqueness of inversion, with which the accuracy of detection can be significantly improved. The focused resistivity method is prospective for advanced detection; with this method, the flanking interference can be reduced and the detection distance is increased subsequently. The time-lapse resistivity inversion method is suitable for the regions with continuous conductivity changes, and it can be used to monitor water inrush in those regions. Based on above-mentioned features of various methods in terms of benefits and limitations, we propose a three-dimensional (3D) induced polarization method characterized with multi-electrode array, and introduce it into tunnels and mines combining with real-time monitoring with time-lapse inversion and cross-hole resistivity method. At last, the prospective applications of DC resistivity method are discussed as follows: (1) available advanced detection technology and instrument in tunnel excavated by tunnel boring machine (TBM), (2) high-resolution detection method in holes, (3) four-dimensional (4D) monitoring technology for water inrush sources, and (4) estimation of water volume in water-bearing structures.

Li Shucai;Liu Bin;Nie Lichao;Liu Zhengyu;Tian Mingzhen;Wang Shirui;Su Maoxin;Guo Qian

Journal of Rock Mechanics and Geotechnical Engineering

2015

© 2017, The Association of Korean Geoscience Societies and Springer-Verlag Berlin Heidelberg. One of the most important issues in the construction of underground water-sealed oil storage caverns is the assessment of their containment properties. These properties depend on the hydrogeological condition and also engineering characteristics of the caverns. Conceptual hydrogeological model for assessing the containment properties of underground water-sealed oil storage caverns was developed. Empirical, numerical and experimental methods for assessing the containment properties were summarized. A principle for the selection of assessment methods was proposed for engineering application. It was proposed that the selected assessment method should be appropriate for the investigation stages, the research objectives and the parameters which have been determined. A five-stage flowchart for the assessment of containment properties of underground water-sealed oil storage caverns was developed. The set of assessment methods was applied to a pilot underground water-sealed oil storage facility in China. Empirical methods, fracture network method and field test methods were presented for the assessment of the containment properties of the cavern, while the other methods were introduced in previous studies.

Qiao Liping;Wang Zhechao;Li Shucai;Bi Liping;Xu Zhenhao

Geosciences Journal

2017

Li Shucai;Shi Shaoshuai;Bu Lin

Nature

2017

© 2017, Springer-Verlag GmbH Germany. While tunneling in karst terrains, engineers may encounter unpredictable well-developed karst conduits, which frequently lead to water inrush accidents. Geological processes significantly affect the varieties and characteristics of water-bearing structures. Therefore, a comprehensive system for water-bearing structure prediction is first put forward, and then the geological and hydrogeological engineering conditions of the Yuelongmen tunnel in Southwest China are analyzed. To accurately predict the geometric characteristics of water-bearing structures and their spatial relationship with the tunnel face, the transient electromagnetic method (TEM) and ground-penetrating radar (GPR) were comprehensively applied. Then, the induced polarization method (IP) was utilized separately to detect the three-dimensional position and spatial distribution pattern of the water-rich area. According to the comprehensive forecast conclusion, targeted boreholes were drilled, which were selected to verify the water-bearing structure in the survey area. The drilling and detection results matched. Furthermore, the curtain grouting method was adopted for the treatment of the water-rich area. By establishing a comprehensive prediction technology system with the principle of “from qualitative analysis to quantitative identification, from structure locating to the water-bearing structure discrimination, as well as from far and near,” this comprehensive prediction system was successfully put into practice in the karst tunnel in Sichuan; it can play a guiding role in similar projects.

Bu Lin;Li Shucai;Shi Shaoshuai;Li Lipin;Zhou Zongqing;Nie Lichao;Sun Huaifeng;Zhao Yong

Bulletin of Engineering Geology and the Environment

2019

© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. While tunnelling in karst terrains, karst fissure water may endanger the safety of tunnel engineering and cause geological disasters such as water inrush. To ensure the safety of tunnel construction, in investigation stage, engineering geological and hydrogeological conditions of Jigongling Tunnel was analysed firstly. In design stage, a reasonable prediction method combining with optimization principle was selected to calculate the water inflow according to the geological and hydrogeological conditions analysed in the investigation stage. Then the advanced geological prediction was divided into different classes based on the water inflow. To make an accurate prediction, tunnel seismic prediction method, transient electromagnetic method, induced polarization method and advanced geological drilling were comprehensively applied in construction stage. This method combined with geology analysis, water inflow calculation and classification of advanced geological prediction is successfully applied in the Jigongling Tunnel of Fanba Expressway, and has provided a reference for the similar engineering constructions.

Shi Shaoshuai;Bu Lin;Li Shucai;Xie Xiaokun;Li Liping;Zhou Zongqing;Xu Zhenhao;Ma Dan;Xiong Ziming

Geomatics Natural Hazards and Risk

2017

© 2017 Elsevier B.V. Due to the special properties of loess, the deformation of tunnels constructed in loess is generally large and easily induced. To control deformation during construction, the degree of influence of multiple factors on tunnel deformation is analyzed by data mining and a deformation prediction model is established, based on tunnels along the Menghua railway of China. Both objective environment and manual operation are considered. The surrounding rock level, groundwater condition, burial depth, excavation method and support close time are selected as the main factors influencing tunnel deformation. The influence degree of each factor is calculated through mining statistical data collected from the project. Finally, using influencing factors as evaluation indices, a Rough set-extension model for predicting loess tunnel deformation is established and tested. Results obtained via the prediction model are in good agreement with field observations. The study quantifies the influence degree of each selected factor on deformation of the loess tunnel, which in turn can help in deformation control efforts. Moreover, the Rough set-extension model realizes a multi-criteria prediction of the loess tunnel's deformation and provides a practical guide for construction of similar projects.

Xue Yiguo;Zhang Xueliang;Li Shucai;Qiu Daohong;Su Maoxin;Li Liping;Li Zhiqiang;Tao Yufan

Engineering Geology

2018

© 2018 An increasing number of tunnels are being constructed with tunnel-boring machines (TBMs) due to the increased efficiency and shorter completion time resulting from their use. However, when a TBM encounters adverse geological conditions in the course of tunnel construction (e.g., karst caves, faults, or fractured zones), disasters such as water and mud inrush, collapse, or machine blockage may result, and may severely imperil construction safety. Therefore, the advance detection of adverse geology and water-bearing conditions in front of the tunnel face is of great importance. This paper uses the TBM tunneling of the water conveyance project from Songhua River as a case study in order to propose a comprehensive forward geological prospecting technical system that is suitable for TBM tunnel construction under complicated geological conditions. By combining geological analysis with forward geological prospecting using a three-dimensional (3D) induced polarization method and a 3D seismic method, a comprehensive forward geological prospecting technical system can accurately forecast water inrush geo-hazards or faults in front of the TBM tunnel face. In this way, disasters such as water and mud inrush, collapse, or machine blockage can be avoided. This prospecting technical system also has reference value for carrying out the forward prospecting of adverse geology for potential TBM tunneling and for ensuring that a TBM can work efficiently.

Li Shucai;Nie Lichao;Liu Bin

Engineering

2018

© 2018 by the authors. In order to assess a concealed karst cave's influence on karst tunnel stability, an assessment model is proposed based on the analytic hierarchy process and a statistical analysis of relevant engineering projects. Major factors are studied and selected as impact factors of the assessment model based on a statistical analysis on a karst cave' s development conditions (karst hydrogeological and engineering geological conditions), construction conditions, and controlling measures. A weight analysis of factors shows that the surrounding rock grade, supporting measurement, formation lithology, unfavorable geology, construction methods, blasting techniques, advanced geological forecast, and groundwater level are the main controlling factors of the tunnel stability when there is a concealed karst cave in the tunnel. Topography and geomorphology, attitude of rocks, monitoring measurement, strata combination, and interlayer fissures are the minor influence factors. Tunnel section shapes, in situ stress, and geological logging are the least important factors. The proposed method is successfully applied to the assessment of a concealed karst cave's influence on the stability of the Huaguoshan Tunnel on the Enshi-Laifeng and Enshi-Qianjiang Expressways. The evaluation result agrees well with the construction site situation. In addition, the result provides good guidance with respect to the implementation of the treatment scheme and effectively avoids accidents in real-time.

Huang Xin;Li Shucai;Xu Zhenhao;Guo Ming;Chen Yucheng

Sustainability Switzerland

2018

© 2018, Canadian Science Publishing. All rights reserved. Due to their high permeability and high strength, pervious concrete piles (PCPs) can improve ground bearing capacity. However, clogging of pervious concrete in practice is a potential disadvantage. To investigate the clogging mechanism of PCPs due to sand piping, a series of laboratory simulation tests is conducted on a developed hydraulic conductivity test system. This testing demonstrates the effects of pervious concrete porosity, grading of fine movable particles, mix ratio of skeleton particles to movable particles, relative density of soil, and distance between PCPs on PCP clogging. The experimental test results show that the hydraulic conductivity of PCP decreases for approximately 70 min and then becomes relatively stable. In addition, it is observed that PCP clogging rarely occurs in cases of low pervious concrete porosity, small movable sand particle size, high sand relative density, and large pile distance. The results also show that measurement of electrical conductivity can be an alternative method of hydraulic conductivity measurement. Based on the test results, preliminary clogging models are proposed.

Cui Xinzhuang;Zhang Jiong;Li Shucai;Jin Qing;Zheng Yingjie;Cui Sheqiang;Chen Darhao

Canadian Geotechnical Journal

2018