Tunnel Seismic Prediction Method Research Articles

Enhancing the safety management of NATM using the tunnel seismic prediction method: a case study

Although NATM is widely applied in modern tunnel design and construction, tunnel construction is still deemed highly risky due to the unknown ground condition ahead of the excavation face. Faults, massive groundwater, fracture zones, and other factors might easily cause great danger to the excavation work. To enhance the safety management of NATM, the tunnel seismic prediction (TSP) method is introduced to help detect unstable ground conditions to prevent the happening of collapses or disasters during tunnel excavation. With the reflected seismic waves collected from several explosions, TSP could produce high-resolution simulated images that, with careful interpretation, will reveal the ground conditions ahead. In this paper, how TSP is incorporated with NATM for better construction safety is presented.

A New Advance Classification Method for Surrounding Rock in Tunnels Based on the Set-Pair Analysis and Tunnel Seismic Prediction System

An advance optimized classification method is proposed to accurately predict the surrounding rock classification based on set pair analysis (SPA) and tunnel seismic prediction (TSP). Several factors that greatly affect rock mass classification are selected as evaluation indices of SPA based on analysis of TSP data. Evaluation indices are divided into five grades according to its response characteristics of seismic wave field, and their membership functions are proposed by using frequency statistical method. Entropy weight method is adopted to determine the weights of evaluation indices, and a SPA model is established for optimized classification of surrounding rock. Engineering application of Shimenya Tunnel of Yi-Ba Highway is taken as a case study, and proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable. The SPA–TSP method can be further used for other tunnel engineering.

Application of comprehensive prediction method of water inrush hazards induced by unfavourable geological body in high risk karst tunnel: a case study

ABSTRACTWhile 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.

Forecast Geological Prediction for Fault and Water Gushing in Deep-Buried Super Long Tunnel

A kind of geological disasters such as fault and water gushing often occurs during the informational construction of deep super long tunnel, which brings momentous disaster and economic loss to construction safety, so the precise and immediate advance forecast to the situation of fault and water gushing has an important theoretical significance and practical value. The theory of geological survey method, TSP(tunnel seismic prediction) method and GPR(ground penetrating radar) method are summarized and analyzed, forecast geological prediction process for fault and water gushing in deep-buried super long tunnel is formulated with the combination of the three methods. Then a deep super long road tunnel named Da Xiang Ling is detected by using the process synthetically, which gains good prediction results. It has a certain guiding significance to similar projects.

Theoretical and Applied Case Studies of Seismic Imaging in Tunnelling

AbstractSeismic measurements during tunnel operations aim at images of maximum spatial resolution. However, there are still principal limitations of the method applied in the tunnel with regard to spatial resolution by the signal frequency and attenuation and by the small angular illumination coverage. A finite‐difference simulation of elastic wave propagation had been performed to compute a synthetic tunnel seismic reflection survey. Synthetic data are used optimizing the best practice tunnel data processing sequence for both P‐ and S‐waves because every step between the acquisition of the seismic data and the derivation of the final image influences the final seismic resolution. Here, especially the use of attenuation models compensate amplitude loss as well as dispersion by an inverse Q‐filtering and the use of a spatially variable velocity model yielding the right image position of a reflecting geological element in space. The transfer and capability of this practice to real tunnel application is finally demonstrated by the case study of the tunnel seismic prediction method in the Koralm tunnel project in Austria.

Finite‐difference modelling for tunnel seismology

ABSTRACTThe diagonal differencing algorithm, which takes spatial derivatives along the diagonals of the finite‐difference grid, is well suited to solve the elastodynamic equations for tunnel seismic modelling because it is accurate and stable at strong low‐order discontinuities of the elastic medium. Spatial high‐order finite‐difference operators increase the accuracy and efficiency of the algorithm except at steps in the elastic properties, where these operators fail. A solution is to use high‐order finite differences in most of the grid but to employ two‐point second‐order operators at low‐order discontinuities. This keeps memory requirements and computational effort on a level that allows 3D simulations on moderately priced PC hardware. Measurements with the commercial tunnel seismic prediction method yield complex seismic common‐receiver gathers with long direct‐wave pulses. Finite‐difference simulations in two and three dimensions reveal that these long pulses are due to P‐wave reverberations in and around the water‐filled shothole. Direct S‐waves originate close to the detonation point by conversion at the shothole–rock boundary. A dispersive, low‐frequency guided wave reverberates with the average S‐wave velocity inside the excavation damaged zone around the tunnel. The guided wave creates multiple body waves inside the undisturbed rock as it reverberates. It carries useful information about the degree and depth of the rock excavation damage but the guided wave often overlaps tunnel surface‐wave modes and may be difficult to extract from seismograms. Receivers should be buried deeper than the extent of the excavation damaged zone so that the guided waves and tunnel surface waves, which circulate around the tunnel, do not dominate seismic records and hide direct S‐waves, reflections or other late arrivals.