Experimental Study On Mechanical Properties Of Lining Concrete In Urban Drainage Deep Tunnel

Due to the continuous development of urbanization and the influence of extreme climate,the problem of urban waterlogging and drainage is becoming more and more serious.The deep tunnel of urban drainage has become a means to solve the problem of urban drainage in developed areas at home and abroad.For the urban deep drainage tunnel in operation,the lining structure of the main tunnel not only bears the pressure of surrounding rock for a long time,but also bears the action of the static and dynamic water pressure in the tunnel,which usually has the characteristic of periodicity,and is subjected to the periodic dynamic water load of many rainy seasons in a stress cycle.Under the long-term action of dynamic and static load,it will cause some damage and deterioration of concrete material properties,thus affecting the durability and usability of tunnel structure.This dissertation takes concrete lining as the research object,and takes the rainfall characteristics and tunnel buried depth of 30-110 meters in Jinan as the research background.The lining concrete is subjected to cyclic loading and unloading tests and rheological disturbance tests to analyze the deformation characteristics of segment lining under long-term load.To provide a certain theoretical basis for improving the long-term stability of lining,the main conclusions are as follows:(1)Conventional compression test of concrete specimens.Using YUMT-1000microcomputer-controlled electrical servo rock mechanics universal testing machine to perform conventional compression experiments on concrete specimens,it is found that the failure of concrete specimens under triaxial compression is slower than that under uniaxial compression,and the brittleness changes are not obvious."Binding" slowed down the brittle failure of concrete specimens.(2)Concrete specimen cyclic loading and unloading test.Cyclic loading and unloading tests were carried out on YUMT-1000 microcomputer controlled electric-servo universal rock mechanics testing machine.The results show that the hysteretic loop "migrates" forward with the increase of the number of cycles.When the upper limit stress is constant,the loading deformation modulus of the specimen increases with the number of cycles.When the upper limit stress is low,the unloading deformation modulus slowly increases with the number of cycles.When the upper limit stress is high,the unloading deformation modulus first increases and then decreases with the number of cycles.When the number of test cycles is constant,the deformation modulus of concrete specimen under loading and unloading first increases and then decreases with the increase of the upper limit stress.With the increase of the upper limit stress(number of cycles),the residual plastic strain of concrete generally increases.The acoustic wave velocity of concrete specimen decreases with the increase of the upper limit stress(number of cycles),while the damage variable increases with the increase of the upper limit stress(number of cycles).The viscoelastoplastic analysis of the creep deformation of concrete is carried out to provide the basis for establishing the rheological disturbance mechanics model.(3)Rheological disturbance test of concrete specimen.The rheological disturbance test of concrete is carried out by TAW-1000 D rock rheological disturbance test instrument.The results show that the creep curve will produce a sudden strain increase after the disturbance load is applied.Under the same perturbation amplitude,the cumulative perturbation deformation of the specimen generally increases with the increase of prestatic load.At lower disturbance amplitude,the cumulative disturbance deformation increases with the increase of disturbance number,while at higher disturbance amplitude,the cumulative disturbance deformation decreases first and then increases slowly with the increase of disturbance number,resulting in hardening phenomenon.In the triaxial rheological disturbance test,the cumulative disturbance deformation of the first disturbance increases with the increase of the prestatic load,and the radial deformation of the specimen is more sensitive to the disturbance load than the axial deformation.By analyzing the disturbance deformation characteristics of concrete specimen,the relation equation between cumulative disturbance deformation and disturbance number is obtained in accordance with attenuation exponential function.(4)Establish a concrete rheological disturbance dynamics model.Combining the analysis of experimental data,a nonlinear perturbation creep element with damage factor D is proposed,which is connected in series with the Burgers model to construct a concrete rheological perturbation dynamics model.The mechanical model parameters are identified,and the experimental values are compared with The comparison of the fitted curves verifies the rationality of the established mechanical model.