Study On Mechanical Responses Of Tunnel-type Anchorage And The Related Slope Of Suspension Bridge Under Static And Traffic Load

Tunnel-type anchorage is a kind of anchor structure which can make good use of the geological conditions in the anchor area,the relatively small amount of engineering,the high of cost-effective and the small disturbance to the surrounding environment.It is widely used in the suspension bridge of mountainous expressway.This thesis bases on the tunnel anchor project of Yaan to Kangding expressway in Dadu River,Sichuan Province,China.On the basis of static analysis,this paper mainly discusses the bearing characteristics of the tunnel anchorage and the stability of the slope under the traffic load.The main results of the specific research are as follows:1)The elastic theory and limit analysis method are carried out to deduce the approximate calculation formula of characteristics of pullout capacity to tunnel-type anchorage.The bearing characteristics and response rules of tunnel anchorage under static conditions(1,3.5,7,10.5 times of designed load of anchor cables)and dynamic conditions(full load,overload,over speed)are revealed.It is concluded that the surrounding rock of anchorage is destroyed locally under the action of 10.5 times of designed load of anchor cables,the surrounding rock of anchorage is destroyed locally,and the stress of the surrounding rock of anchorage will redistribute,and the stress redistribution curve of the surrounding rock is given.2)Base on the theoretical analysis method,the anchor gravity has a great influence on the side friction of the anchorage under the action of 1 time of designed load of anchor cables,the results of the distribution pattern of side friction are obviously different from that of 3.5 times,7 times and 10.5 times.In state of the anchorage was applied with different load,The results of theoretical calculation and numerical simulation are compared and analyzed,according to analyze the comparison error,the error size is in the range of 10%?30%.3)FLAC3D numerical simulation and theoretical analysis method are used to calculate the dynamic response of tunnel-type anchorage under traffic load,the speed of the vehicle is the main factor to the fluctuation period of the anchor bearing characteristics,and the overload and the full load are the main factors influencing the size of characteristics of pullout capacity to the anchorage,which is not the main influencing factor of the response period.4)According to the numerical simulation of FLAC3D,the stability of tunnel-type anchor slope is analyzed in different engineering conditions,the conditions contain with the natural state,designed load of anchor cables,over-pulling load of anchor cables,full load?overload?low speed?normal speed?high speed?overspeed of traffic load and so on.The model of potential instability happened on shallow surface in the natural state and the tunnel excavation condition,the corresponding factor of safety is 1.52,under other engineering conditions the potential sliding surface of the slope is supported and the stability is improved,the factor of safety of slope is about 1.64.In the case of over speed and 10 times of overloading,traffic load has little effect on the stability of the slope,but it has a certain influence on the anchor characteristics of pullout capacity and it is equavilent to loading effect of 88.9%design pull force of the cable.The mechanical responses of tunnel-type anchorage and their slopes under static and traffic loads are sufficiently given,which can provide theoretical guidance and reference for engineering design of tunnel-type anchorage and the related slope.