Parameter Inversion And Stability Analysis Of Surrounding Rock Of Expansive Rock Tunnel

The article takes south Lvliang mountain expansive rock railway tunnel as the engineering background.Expansive rock tunnel region stability problems are studied.The disease evolution law and disease mechanism in this area are expounded by sorting out and analyzing geological data and disease situation.Based on the experimental data of the expansive rock in this area,the expansion and softening characteristics of the gypsum-bearing marl around the tunnel were studied and discussed.Due to disease treatment scheme and checking calculation of tunnel,but the expansion of the tunnel surrounding parameters can't clear,so based on the above study and put forward by inversion expansion parameters of surrounding rock of tunnel disease characteristics to get ideas,and then according to the monitoring data,the stress and deformation of retaining structure,the inversion results verified the corresponding expansion parameters of surrounding rock.According to this parameter,the safety of three different treatment schemes for tunnel diseases was checked and compared,and the optimal treatment scheme for tunnel diseases was obtained.Since the tunnel diameter of the optimal treatment scheme is larger than the original support scheme,it is necessary to dismantle the lining and excavate the surrounding rock of the original tunnel,so the 3d modeling analysis of the measure is carried out,and the effect of the excavation expansion is studied and some Suggestions are put forward.Finally,by analyzing the parameter sensitivity of the softening coefficient,expansion coefficient and water content increment of the surrounding rock under the original support scheme and the optimal treatment scheme,the leading factors leading to the expansion failure of the lining and the effect of the treatment scheme are obtained.The research results provide reference for support design optimization of expansive rock tunnel in practical engineering.Specific research results are as follows:(1)the disease situation of south Lvliang mountain tunnel is characterized by long cycle,many disease types and large scale.Its geological structure and adverse geological conditions provide objective conditions for the development of diseases.Finally,under the coupling action of high in-situ stress,expansion and softening of tunnel surrounding rock and sulfate erosion,the tunnel support structure is destroyed.(2)when gypsum containing marl expands,its expansion rate and expansion water absorption will increase with the increase of time and eventually become stable,while its expansion coefficient will gradually decrease with the increase of water absorption and finally become stable.For the softening property,only poisson's ratio increases with the increase of time after the rock absorbs water,while other parameters decrease.(3)after disease simulation of the characteristic section,it is found that the maximum expansion range of the characteristic section is 13m,the expansion coefficient is 0.139,and the water content increment is 0.6%.Then this parameter is used to check the three treatment schemes,and it is found that the supporting combination of circular tunnel and relief and backfill holes is the optimal treatment scheme.(4)after the lining demolition and surrounding rock excavation analysis of the tunnel,it is found that a small footage should be used,and the footage should not be more than 4m,the grouting reinforcement radius of the expansion section should not be less than 9m,and at least the adjacent tunnel within 4m of the expansion end face should be protected.(5)The results of sensitivity analysis of dilatation-softening parameters show that,under the original support scheme,the sensitivity of each parameter is as follows:expansion coefficient>moisture content increment>softening coefficient;Under the treatment scheme,the sensitivity degree of each parameter is successively:expansion coefficient=water content increment>softening coefficient.Comparing the two schemes,it can be found that the treatment scheme can effectively reduce the sensitivity of each parameter and make the sensitivity of each position of the tunnel to the expansion softening parameter in a similar range,so as to enhance its structural stability.