Optimization Study of Surface Precipitation Parameters for Water-rich Weakly Cemented Sandstone Tunnel
Water-rich and weakly cemented sandstone strata have poor rock formation and very sensitive water stability characteristics,which are easy to destabilize into flow plasticity and cause disasters.In order to ensure the safety of tunnel construction,a tunnel project is relied on to carry out the optimization study of surface precipitation parameters.Through the combination of numerical model and field test,the influence of surface deep well precipitation time,spacing and pipe diameter on the groundwater level around the tunnel was analyzed.The numerical results show that:when surface ultra-deep wells are used for precipitation,the groundwater level in the sandstone formation first drops significantly and then gradually stabilizes.As the spacing of the descending wells decreases and the diameter of the descending wells increases,the groundwater level after stabilization of the descending water gradually decreases.From the effect of precipitation,the spacing of precipitation wells is the main factor affecting the groundwater level,and the experimental results are in good agreement with the numerical results.Taking multiple factors into consideration,the parameters of the ultra-deep well precipitation wells in sandstone formation are recommended to be:spacing of 16 m,diameter of 600 mm,and 90 d of pre-precipitation time.The research results can provide reference for the safe construction of water-rich sandstone tunnel.
water-rich sandstone tunnelsurface precipitation optimizationnumerical simulationspacing of precipitation wellsdiameter of precipitation wells
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