Effect Of Impact Load Of Pile On Adjacent Tunnel By Using Numerical Simulation

With the rapid development of modern urban construction and urban rail transit, subway and building construction is often carried out at the same time, accompanied by a living.The impact load generated by the piling can produce vibration and deformation, stress damage to the tunnel, and that causes a security risk to the normal operation of the subway and the personnel travel.In order to analyze the effect of piling on the whole structure of the tunnel, and to put forward the feasible suggestions of the project construction and metro operation, numerical code RFPA-dynamic is mainly used to set up the numerical model for the actual project to study and to discuss the stress and vibration effect of tunnel due to the pile under impact load from single homogeneous soil layer model to the actual soil model. The propagation of stress wave in medium and the process of stress and failure of tunnel lining are also directly demonstrated.The main contents are as follows:1.In order to verify the reliability of the model established in this paper to study the influence of piling on the tunnel, reference the same parameters to simulate the physical experiment that has been finished, and analyse the law of crack propagation of the beam containing unilateral pre-existing cracks under drop impact load to verify the feasibility of the numerical model by comparison.2.Establish the soil-structure interacted model with a single homogeneous medium according to the actual geological conditions. Simulate the influence of piling on tunnel lining structure under different impact loads (peak value of stress wave), different depth and different distance, and compare the influence of impact load on tunnel in different deformation modulus soil medium. Analyse the stress response of each position, distinguish the adverse effect area,and discuss the failure mode of the lining structure through the numerical test results.3.Establish the numerical model according to the actual geological condition. Analyse the dynamic response of tunnel lining structure under different impact loads, different depth and different distance when the reflex action at the junction of different rock layers and the scattering effect due to heterogeneous soil is considered. Compare with the model of single homogeneous soil layer and put forward suggestions for the actual project through the stress, vibration velocity and other results.Combined with the numerical simulation of the homogeneous soil model and the actual project, the following research law is obtained:The upper 1/4 arc section of the lining structure near the side of the pile is most obviously affected by the impact;The stress response of the lining is more obvious, the vibration velocity and displacement are more greater, and the tunnel is more easier to be damaged when the higher the pile energy or the stress wave peak is. It is the most unfavorable to the lining structure when the relative distance between the pile bottom and the tunnel center is relatively close. When the pile bottom is more than the tunnel depth, the effect of pile driving on the lining of the tunnel is gradually weakened; When the distance between pile and tunnel is farther, the stress wave attenuation is greater, and the influence of the stress wave is smaller. But when the tunnel isn't buried deep and the piling depth is shallow, and there are many kinds of soil layer interface, stress wave reflex in the interface between soil and air and the interface of different soil layers, that will superposite with the stress wave of direct transmission to cause more adverse impact on the tunnel lining; When the deformation modulus of soil layer is greater, stress wave propagation is faster and the energy loss is smaller, so the impact of the adjacent tunnel is more obvious.Through the research on the construction process of piling on adjacent tunnel effects analysis, it has very important application value to the design and construction of the subway tunnel, operation of Metro Transit, subway daily monitoring and maintenance, engineering construction safety management.