Simulative Analysis Of Loess Cave Static Force Characteristics In East-Central Gansu Province

The numerous people live in a large number of caves in the east-central of Gansu province.The cave is a kind of green ecological architecture,it not only saves energy but also building material and land.The utilizing of loss caves can let local inhabitants to put a lot of money into education and production for the undeveloped east-central of Gansu province,it can let this region overall development to get better balance and assurance,so the cave still has its value of existence and research.The accidents of loess cave engineering happen repeatedly. It is necessary to study the regularities and its influence factors of loess cave.The home and abroad experts achieve many research results. To the strength and rigidity of caves,some scholars simplify it as plane strain problem and analyze it with finite element method, finally they draw some results. The author uses the three-dimensional model to process this problem for having more real solutions. According to range of loess parameters and cave sizes in the east-central of Gansu province the author makes more than 1,000 calculations and serves as the project's reference.Utilizing the east-central Gansu loess region as the background , on the elastic-plastic theory the three dimensional finite element models were built in the article,the calculation is finished with MIDAS / GTS. Through calculating a lot of cave models and discussing the loess parameters,the width of cave and the height of straight wall,the curve forms of the cave vault,the cave lining,the buried depth of caves to influence the strength and rigidity of soil body around the cave some basic regularities are obtained:1. The maximum and minimum displacement algebraicvalue of soil body around the cave respectively appeared at the midpoint of bottom edge and the vertex of arch in all of calculation models.2. The plastic zone appeared at the join point of straight wall and arch first and the range of plastic zone changed with the calculated parameters change in all of calculation models, but the position of maximum equivalent plastic strain was unchangeable on the whole.3. The influence of loess physical parameters was linear to the displacement of soil body around the cave,the soil gravity was the most sensitive to the displacement of soil body around the cave;the influence level of loess physical parameters wasγ,c,φin turn;The influence of cave sizes was linear to the displacement of soil body around the cave,the absolute value of displacement changed modestly with increasing of the height of straight wall,so it was almost negligible.4. The influence of soil gravity was the most sensitive to the value of maximum equivalent plastic strain in 3 loess physical parameters,soil cohesion was more sensitive to the expanded cave plastic zone than soil angle of internal friction;Cave width was more sensitive to the expanded cave plastic zone than height of straight wall. 5. The displacement of soil body around the cave and the value of maximum equivalent plastic strain were the smallest for the parabolic vault curve,the influence level of the curve forms of the cave vault were the parabolic vault curve,the circle vault curve,the dual-core circle vault curve in turn.6. The vertical displacement of cave and the maximum equivalent plastic strain value of cave were decreased after lining,so the lining was the necessary means to improve the caves of rigidity and safety.7. The minimum safety distance between in caves was 5.6 meters.