| ABSTRACT:With the increasing of the number of operational tunnel and the tunnels’ operation time, tunnel disease has appeared in different degree in many tunnels, such as the lining deformation, crack damage, damage to the track bed, and water leakage, which threatens the driving safety severely. Many things cause the appearance of the tunnel disease, among which, the voids behind the lining is one of the main reasons. The existence of voids behind the lining changes the interaction between the lining and the surrounding rock, deteriorates the stress state of the lining, and causes the production of the lining disease. Accurately determination of the stress state of the lining has important significance for the tunnel disease prevention and treatment of tunnel disease. For clearing the stress state of the lining in the state of the existing of void behind the lining, the distribution of rock pressure of this state, the influence of tunnel depth, surrounding rock grade and other factors on the distribution of rock pressure, and the safety factor calculation model of this state are studied by the method of numerical simulation. Main research work and research results are as follows:(1) The existence of voids behind the lining, changes the transfer path of the load, changes the distribution of rock pressure, and causes the formation of two region on both sides of cavity, in one rock pressure increases and in another rock pressure decreases.(2) The average stress-increasing factors and the stress-increasing region is used to characterize the stress-increasing region. And the average stress-increasing factors will decreases with increasing rock grade, increasing tunnel depth, and increasing linging thickness, and will increase with the size of the voids and releasing factor; the stress-increasing region will increase with the size of the voids, the rock grade, tunnel depth and linging thickness will decreases with increasing releasing factor.(3) For the combination of the cavity, when the cavity is small, or is far away each other, Superposition effect is weak between the voids, and the rock pressure distribution and deformation of lining is the same as which only one void exists; when the cavity is large, or is close each other, the effect region of the voids will overlap, in which the rock pressure distribution will change, and the safety of the linging will decrease.(4) Based on the above conclusions, a loading model of the load-structure model is put forward where the influence of the increasing rock pressure zone is considered. At last, an example is provided to analyze the difference of lining safety of the two load models, one takes the influence of the increasing rock pressure zone into consideration and the other does not. The results show that the safety factor of the lining decreases and the most dangerous position changes from the center of the void to the two sides. |
PDF Full Text Request