| The number and total mileage of tunnels in our country have been in the forefront of the world.However,with the increase of tunnel operating time,the problem of tunnel diseases is increasing day by day.Among them,the void behind the lining is the most common quality defect of the tunnel,which is the main cause of tunnel disease.The void behind the lining will deteriorate the surrounding rock-lining contact relationship,change the mechanical characteristics of the lining structure and the stress distribution law of the surrounding rock,which threatening the operational safety and service life of the tunnel.This paper is based on literature review,mathematical statistics,numerical simulation,on-site inspection and other methods to study the tunnel's mechanical properties and safety which influcenced by the void behind the lining.The main research results are as follows:(1)From the aspects of tunnel design concept,construction quality control and operation maintenance,the general causes of the void behind the tunnel lining are summarized in this paper.(2)Based on the nondestructive testing data of more than 100 highway tunnels,the general rule of void distribution is obtained.The statistical results show that:(1)The void behind the lining is mainly distributed in the arch,and the void behind the arch lining accounts for 95% of the total.(2)The length distribution of the void behind the lining is discrete,in which individual tunnels have the void along the tunnel.The height of void is mainly distributed in the range of 0~20cm,and the average length and height of the void of the lining basically follow the general law: vault > arch waist > side wall,V class surrounding rock > IV class surrounding rock > III class surrounding rock.(3)Through statistical model analysis,the heights of the vault,arch waist and side wall are all right-off and spike distribution.Finally,the distribution curve of the void height is fitted based on MATLAB software,and the probability distribution function of the height of each position is obtained.(3)Based on the stratum-structure model,the influence laws of the small-scale void behind the arch lining on the tunnel structure is studied,and the influence laws of the location of the void,the range of the ring direction of the void and the radial height of the void on the internal force of the lining,the safety coefficient of the lining,the contact pressure of the surrounding rock-lining and the stress distribution of the surrounding rock is obtained.The results of the study are as follows:(1)The stress concentration phenomenon of lining structure is produced on the edge of both sides of the void,and the safety factor of lining structure in the void range is obviously reduced,which reduces the overall safety of the lining structure.(2)Under the calculation condition in this paper,with the increase of the range of symmetrical void in the arch,the overall safety of the lining structure decreases,and the phenomenon of stress concentration at the edge of the void is more obvious,but the overall contact pressure tends to decrease.The stress relaxation zone of surrounding rock tends to increase with the increase of circumferential range of void,while the height of the symmetrical void in th arch has little effect on the overall safety of tunnel structure,but with the increase of void height,the phenomenon of contact stress concentration on the edge of void is more obvious.(3)The influence on the mechanical properties and safety of the lining under the condition of asymmetric void behind the lining of arch is similar to that under the condition of symmetrical void.However,the phenomenon of contact pressure concentration under the condition of asymmetric void is more significant than that under the condition of symmetrical void.The stress distribution of surrounding rock is greatly affected by the surrounding rock stress distribution.When the deflection angle range is 50% of the the ring direction of the void,the surrounding rock stress distribution is most affected by the void behind the lining.(4)This paper summarizes the common measures for controlling the void behind the lining,and focuses on the theoretical calculation of the measures of grouting treatment of void.The influence of different grouting pressures on the safety of lining structure and the stress of surrounding rock is obtained when the grouting pressure is used to control the void behind the lining,and some optimization suggestions are given for the grouting mode with different dimensions viod behind the lining.(5)This paper relies on the rectification(construction of civil engineering)of a provincial road tunnel to verify and apply the theoretical research results.The overall safety of the tunnel structure before and after treatment is compared and analyzed by numerical calculation.Furthermore,the effect of the void grouting behind the lining is verified by the method of non-destructive testing of the ground penetrating radar. |
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