Abstract
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.
Highlights
In recent years, the construction of tunnels in China is developing rapidly, which is the largest number and widest scale in the world
Due to the complex hydrogeological conditions in the tunnel area, there are a variety of geological hazards, especially water inrush and mud gushing caused by large water-bearing structures and unfavourable geologic bodies (Wang 2004; Li et al 2007; Li et al 2010; Li et al 2016; Chen et al 2011; Shi et al 2011; Shi et al 2013)
Some water inrush accidents occurred in Huayingshan Tunnel, the maximum inflow reached up to 14,400 m3/d and the amount of sand discharge was over 1 million m3; at K30+900 of Wuzhishan Tunnel, the maximum inflow was about 4.3 £ 104 m3/d and the spurt distance of water column was over 10 m(Liu et al 2006; Li et al 2008; Li et al 2009)
Summary
Water inrush were observed in ’DK124 + 602’ karst tunnels on 5 August 2007, and the peak flow rate reached 1.5 £ 105m3/h, causing the equipment and machinery in the tunnel to be seriously deformed and/or damaged, flooded about 500 m away from their positions. The damage caused by water inrush with high pressure and large capacity is obvious, accurate prediction and effective governance of water-bearing structures are important problems to be solved (Zhao et al 2013; Shi et al 2014). With the increasing tunnel engineering build in geological complex karst zone, the accurate and timely forecast of the fissure water is the key to study and solve problems in tunnel engineering design and construction. Based on a large number of engineering experiences, this paper presents a prediction method of fissure water inrush in high-risk karst region, verified by engineering application
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