Study On Deformation Law Of Surrounding Rock Of Shallow-buried Bias Tunnels With Small Interval

In the construction process of the mountain tunnel,due to the constraints of tunnel selection,engineering geology and other factors,as well as consideration of construction technology,engineering cost and other factors,the small clearance tunnel has been widely used in the construction process.Compared with the traditional small-pitch tunnel,the deformation and stress characteristics of the surrounding rock of the shallow-buried biased small-space tunnel are more complicated,especially the shallow buried side of the tunnel.It is easy to cause engineering accidents such as collapse and roof collapse during tunnel construction.It is important to study the deformation law of surrounding rock during construction of shallow-buried bias tunnels with small interval to ensure the safe construction of the tunnel.This paper takes the Huangjiakuang Tunnel of the Tianhezhi Hot Spring Section reconstruction project of Weihai S201 Weidong Line as the engineering background,and uses MIDAS GTS NX finite element software to analyze the surrounding rock forces and deformation during the actual construction process of shallow-buried bias tunnels with small interval step method.Regularity,plastic zone of surrounding rock and surface subsidence law were studied.Combined with the field measured data,the surface settlement,arch settlement and surrounding convergence of shallow buried bias small clearance tunnel are summarized and compared with the simulation results.The BP neural network model is used to realize the tunnel dome.The real-time prediction of rock deformation is carried out.Finally,the influence law of tunnel surrounding rock deformation with different depths,different clearances and different bias angles is systematically studied.The specific research contents are as follows:1.By reading a large number of domestic and foreign literatures,the methods for determining shallow tunnels,bias tunnels and small clear tunnels are summarized.The calculation method of surrounding rock pressure of s shallow-buried bias tunnels with small interval and the deformation law of tunnel surrounding rock and BP neural network related theoretical methods are summarized and summarized,which lays a theoretical foundation for the surrounding rock deformation analysis and settlement prediction.2.Based on the actual conditions of the shallow buried and biased small-clearance tunnel at the entrance of Huangjiakuang Tunnel,a three-dimensional numerical analysis model was established.The displacement and stress fields during the tunnel construction process and the dynamic evolution process of the plastic zone were analyzed and obtained.The ground settlement law and vault settlement law during the tunnel construction process,that is,the final horizontal lateral settlement tank of the tunnel is a "W" type with a large settlement on the left and a small settlement on the right.The surface settlement in the center of the left settlement tank is about right.The settlement value of the center of the side settlement tank is 1.41 times;the surface settlement of the tunnel can be divided into 4 stages,namely the micro-settling stage,the subsidence-enhancing stage,the subsidence-stabilizing stage,and the subsidence-basic-stabilizing stage.Before excavation,the subsidence intensification stage is mainly the excavation of the upper steps of the tunnel;the law of settlement of the arches on the left and right lines of the tunnel is basically the same,that is,it has experienced three stages of rapid growth,slow growth,and basically stability.The stage of rapid increase in tunnel deformation is mainly the tunnel.The excavation of the upper steps,so in the tunnel excavation stage,attention should be paid to strengthening the monitoring and measurement of the steps on the tunnel For;The results show that strain and stress are within the surrounding rock tunnel rock construction safety range,so step method can be used to construction of IL home bias of the shallow Neighborhood Tunnel.3.Based on the field measured data,the deformation rules of the surrounding rock of the shallow-buried and biased small-clearance tunnel are summarized.The research results show that the ground surface settlement law and vault settlement law of the tunnel are basically consistent with the simulation results.It mainly occurs in the excavation of the upper step;it can be obtained from the measured peripheral convergence data that the peripheral convergence value has gradually increased to a stable process.The typical sections of the left line tunnels ZK5 + 550,ZK5 + 560,and right line tunnels YK5 + 546,YK5 + 556 were selected as the research objects.The traditional regression functions,namely the exponential function,the logarithmic function,and the hyperbolic function were used for the four sections.Regression analysis of the arch settlement data showed that the arch settlement of the Huangjiakuang Tunnel was the fastest stage of deformation rate development in the range of 0 ? 15 days,the deformation rate of the surrounding rocks slowed down in 16 ? 45 days,and the state of the surrounding rocks was basically stable in about 50 days.Finally,the BP neural network was used to predict the surrounding rock deformation of the tunnel.The analysis results show that the relative error of the regression function is higher than the neural network prediction in the early stage of tunnel construction,and the prediction accuracy of the two prediction methods in the later stage of construction is basically the same.The deformation law of the surrounding rock in the early stage of the tunnel can be predicted by the BP neural network method.For the deformation law of the surrounding rock in the later stage of the tunnel,the two methods can be combined to comprehensively predict.4.Based on the actual conditions of the project,combined with numerical simulation methods,the effects of tunnel burial depth,clearance and bias angle on the deformation of the surrounding rock of a shallow buried bias small clearance tunnel are studied.As the buried depth of the right-line tunnel increased from 5m to 20 m,the settlement of the vault of the left-line tunnel increased from 24.7mm to 46.5mm,and the settlement of the vault of the right-line tunnel increased from 6.6mm to 28.7mm.The settlement of the tunnel vault increases with the increase of the tunnel burial depth;under the same burial depth and bias angle,the tunnel's settlement on the right line is 13.1 when the clear distance B = 6m,12 m,18m,and 24 m,respectively.mm,11.5m,11.5mm,and 11.2mm,indicating that the change of tunnel clear distance has little effect on the dome settlement.Under the same burial depth and clear distance conditions,when the bias angle is 0 °,15 °,30 °,45 °,the settlement values of the right-line tunnel vault are 12.3mm,10.9mm,11.5mm,and 16.5mm,respectively.The 7-8 convergence values of the step line are 1.96 mm,3.26 mm,3.6mm,and 7.44 mm,respectively.When the bias angle is 45 °,it has the most significant effect on the settlement of the right-line tunnel vault and the convergence around the upper step.Under all conditions,the settlement value of the vault on the deep-buried side and the surrounding convergence value are greater than those on the shallow-buried side,and the settlement value of the vault on the tunnel excavation on the steps accounts for more than 80% of the total settlement value.