Liu Zhengyu

Bio: Liu Zhengyu is an academic researcher from Shandong University. The author has contributed to research in topics: Radar & Drill bit. The author has an hindex of 12, co-authored 109 publications receiving 692 citations. Previous affiliations of Liu Zhengyu include Structural Engineering Research Centre.

Detecting and monitoring of water inrush in tunnels and coal mines using direct current resistivity method: A review

Abstract: 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.

A rapid four-dimensional resistivity data inversion method using temporal segmentation

Abstract: 4-D electrical resistivity tomography (ERT), an important geophysical method, is widely used to observe dynamic processes within static subsurface structures. However, because data acquisition and inversion consume large amounts of time, rapid changes that occur in the medium during a single acquisition cycle are difficult to detect in a timely manner via 4-D inversion. To address this issue, a scheme is proposed in this paper for restructuring continuously measured data sets and performing GPU-parallelized inversion. In this scheme, multiple reference time points are selected in an acquisition cycle, which allows all of the acquired data to be sequentially utilized in a 4-D inversion. In addition, the response of the 4-D inversion to changes in the medium has been enhanced by increasing the weight of new data being added dynamically to the inversion process. To improve the reliability of the inversion, our scheme uses actively varied time-regularization coefficients, which are adjusted according to the range of the changes in model resistivity; this range is predicted by taking the ratio between the independent inversion of the current data set and historical 4-D inversion model. Numerical simulations and experiments show that this new 4-D inversion method is able to locate and depict rapid changes in medium resistivity with a high level of accuracy.

Tunnel construction large-scale integrated geophysical advanced detection model test device

Abstract: The present invention discloses a tunnel construction large-scale integrated geophysical advanced detection model test device. The model test device includes a tunnel surrounding rock, a main tunnel model, a model test case, a water-containing geological structure device, a numerical control automated construction device and a main control chamber. The model test device is a large-scale integrated geophysical advanced detection model test device meeting the detection using a seismic wave method, an electromagnetic method and a direct-current electric method. By using the geophysical advanced detection model test device, the geophysical response features of the water-containing geological structure device in front of a tunnel face may be studied, multiple geophysical advanced detection forward and inversion methods for the water-containing geological structure device are verified, and the relationship between some geophysical detection method results and water burst quantity is studied, so as to lay a test foundation for the advanced prediction and water burst quantity prediction of the water-containing geological construction device in actual engineering.

Comprehensive advanced geological detection system carried by tunnel boring machine

Abstract: The utility model discloses a comprehensive advanced geological detection system carried by a tunnel boring machine. The comprehensive advanced geological detection system comprises a multifunctional combination host, an induced polarization detection device, a seismic wave detection device, an integration wiring device and a drilling geological radar detection device. The multifunctional combination host comprises an excitation source control module and a parallel data collection module. Output trigger signals are sent to the three detection devices through the excitation source control module and the three detection devices output measured data and feedback signals through the parallel data collection module. The comprehensive advanced geological detection system has the advantages that the degree of automation and detection speed of detection apparatuses on the tunnel boring machine are greatly increased and it is possible for the tunnel boring machine to carry multiple detection apparatuses.

Method for assessing coal-floor water-inrush risk based on the variable-weight model and unascertained measure theory

Abstract: Water inrush from coal-seam floors greatly threatens mining safety in North China and is a complex process controlled by multiple factors. This study presents a mathematical assessment system for coal-floor water-inrush risk based on the variable-weight model (VWM) and unascertained measure theory (UMT). In contrast to the traditional constant-weight model (CWM), which assigns a fixed weight to each factor, the VWM varies with the factor-state value. The UMT employs the confidence principle, which is more effective in ordered partition problems than the maximum membership principle adopted in the former mathematical theory. The method is applied to the Datang Tashan Coal Mine in North China. First, eight main controlling factors are selected to construct the comprehensive evaluation index system. Subsequently, an incentive-penalty variable-weight model is built to calculate the variable weights of each factor. Then, the VWM-UMT model is established using the quantitative risk-grade divide of each factor according to the UMT. On this basis, the risk of coal-floor water inrush in Tashan Mine No. 8 is divided into five grades. For comparison, the CWM is also adopted for the risk assessment, and a differences distribution map is obtained between the two methods. Finally, the verification of water-inrush points indicates that the VWM-UMT model is powerful and more feasible and reasonable. The model has great potential and practical significance in future engineering applications.