| This paper takes the tunnel under construction in Lu Jiazhai as the object,and deduces the theoretical formula of seepage field under the condition of homogeneous surrounding rock,karst cave and permeable interlayer combined with the groundwater seepage theory.In order to explore the influence of displacement on the distribution law of water pressure around the tunnel,the model test was carried out according to the similarity principle.Due to the diversity of underground water types in the tunnel in the water-rich area,the sources of water inrush were identified by the combination of gray correlation method and time series method,and the numerical simulation calculation was carried out on the background of Lu Jiazhai tunnel to further explore the influence form of displacement on the water pressure distribution around the tunnel.By monitoring the water surface height of wells around the tunnel area,the effect of the intelligent drainage valve on groundwater control is reflected.The main research contents of this paper are as follows:(1)Based on the engineering groundwater calculation theory,the relationship between the tunnel displacement and the water pressure behind the lining under the condition of homogeneous surrounding rock is deduced.Considering the conditions of karst cave geology and permeable interlayer,the calculation formulas of underground water potential field and flow field under karst cave condition and the calculation formulas of flow field under permeable interlayer condition are derived.According to the model test based on the actual situation of the project,it is found that when the displacement is 2.5m~3/d·m(0.75m~3/d),the distribution law of water pressure on the outer surface of the grouting ring and behind the lining is basically consistent with that without drainage.When the displacement is 1.5m~3/d·m(0.45m~3/d),the water pressure value behind the grouting ring and lining is greater than that without drainage.The water pressure value behind the lining increases first and then decreases with the increase of displacement.When there is a weak permeable interlayer,the distribution of seepage pressure behind the lining is similar to the theoretical calculation results,with an average error of 1.44%.When the displacement increased from 2.5m~3/d·m to4.0m~3/d·m,the water pressure behind the lining in the condition without interlayer decreased by 11.91%and the outer surface of the grouting ring decreased by 0.74%.In the case of interlayer,the water pressure behind the lining is 12.02%,and the outer surface of the grouting ring decreases by 0.67%.It indicates that the increase of displacement has obvious effect on the reduction of water pressure behind the lining,but not on the external surface of the grouting ring.It is feasible to control the water pressure behind the lining by controlling the displacement.(2)The relationship between the content of ions in gushing water and the source of gushing water,rainfall and gushing water were discussed.The grey correlation analysis and time series method are combined to identify the water inrush source.The method can identify the water inrush source of five water inrush points well,and obtain the approximate time when the rainfall signal arrives at each water inrush point,including 5days at point B,5 days at point D and 8 days at point E.The intelligent control device of groundwater is developed.Based on Mohr-Coulomb constitutive relation,the typical watershed rich mountain tunnel numerical model,the seepage calculation of different drain permeability coefficient under different grouting circle of permeability coefficient,water pressure distribution rules of surrounding rock and lining on the sensitivity analysis,reveals the different factors on the impact water pressure distribution regularity of grouting circle and lining inside,found by changing the scupper permeability coefficient,the more effectively change the displacement control of grouting circle water pressure value.(3)Through the water level observation of the surrounding Wells,it was found that after the use of the intelligent drainage valve,the water pressure drop rate at point B decreased from 22.84%to 15.98%,point E decreased from 11.05%to 9.99%,the water level reduction rate of the Wells reduced to 10%when no drainage valve was used,indicating that the drainage valve has a good effect on the control of the groundwater level;After setting the drainage valve as an intelligent treatment,it was found that the fluctuation range of the water pressure value of B and E points became smaller,indicating that the drainage valve had a good effect on the water pressure control in the surrounding rock.After the use of the new technology,the probability of water inrush accident is reduced from 1 time/month to 0.2 time/month,which improves the safety factor of the construction process. |
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