Tunnel engineering is inherently concealed, often susceptible to various adverse geological conditions. In the absence of accurate forecasts or predictions of potential adverse geological conditions before or during tunnel construction, it could impact project progress and even lead to catastrophic accidents. Through advanced forecasting, timely identification of anomalies becomes possible, enabling forecasts of the location, characteristics, surrounding rock structure integrity, and potential water content of adverse geological formations ahead of the tunnel face. This information forms the basis for proper excavation section selection, support design parameters, and optimized construction strategies. Additionally, it facilitates timely information for preventing disaster-prone accidents like tunnel water inundation and sudden mud inflows. Adequate preparation for construction safety is ensured, while substantial cost savings are also achievable. This approach bears immense significance in tunnel construction.
Tunnel advanced geological forecasting encompasses methods such as geological survey, advanced drilling, geophysical prospecting, and pre-excavation forecasting methods. Each forecasting approach comprises the following aspects:
Geological Survey: This involves supplementary surface geological surveys for tunnels, in-tunnel face geological sketches, tunnel bore geological sketches, underground and surface correlation analysis of stratigraphic and structural lines, geological mapping, and more.
Advanced Drilling: This includes advanced geological drilling, deep borehole detection, and in-hole photography.
Geophysical Prospecting: Methods encompass elastic wave reflection techniques (seismic wave reflection, horizontal acoustic profiling, negative velocity method, and minimal-offset high-frequency continuous reflection profiling, among others), electromagnetic wave reflection methods (ground-penetrating radar detection), high-resolution direct current method, infrared detection, and more. Elastic wave reflection techniques encompass TSP, TST, TRT, HSP, among others. Among them, seismic wave reflection method (TSP) and ground-penetrating radar method (electromagnetic wave reflection) yield notable outcomes.
Pre-Excavation Forecasting via Pre-Excavation Shafts: This involves methods like parallel pre-excavation shafts and straight tunnel pre-excavation shafts.
Each method contributes to comprehensive tunnel advanced geological forecasting, ensuring proactive measures for construction safety and efficiency.