A Finite Element Approach For The Contact Problem Of Anchor Bolts And Its Application

So far, though the anchor bolts are widely used in tunnel, slope and deep excavation engineering for their convenience in construction and good effect, the theory on the calculating and design method of anchor bolts studies are not so perfect and remain to be developed. Presently, though finite element method is still an ideal tool for the calculation of anchor-bolt retaining structures and many research results concerning these problems are available, there exist some problems on these methods in simulating the anchor bolt's mechanical behavior. The main intention of this paper is to develop a reasonable, simple, applicable computational model and corresponding finite element approach about anchor bolts, and to apply it to geotechnical problems of anchor-bolt retaining.By the analysis of the present computational models and methods on anchor bolts, the author deems that there are some disadvantages in these methods, such as: (1) the models can't reflect the relative slide between the bolts and geotechnical mass; (2) the division of FEM mesh is too complicated; (3) some computational parameters of the bolts are difficult to determine. Thus, the author attempt to develop a new model of anchor bolts so as to avoid the disadvantages. In the model, the interaction between the bolt and the geotechnical mass is taken as contact problem, in which if the tangential force at the interface has reached the limit resistance, the relative slide in the interface will occur along the tangential direction. Also, the computational parameters in the model have tangible physical meanings and have less difficulty to obtain. Otherwise, the existence of the bolt element adds no trouble on the division of the mesh.Based on the aforementioned theory, the relevant formulae and program of FEM are developed. Two examples concerning pullout test of rock bolt and an anchor bolts reinforcing slope are calculated and analyzed. The ideal results have verified the validity of the method and its ability to solve the problems in engineering.In conclusion, compared with the existing methods, the model developed by the author can simulate the mechanical behaviors of anchor bolt more perfectly and the relevant parameters can be gained more easily. Furthermore, the program is easy in implement and convenient in use. Thought it is not so perfect asexpected up to now, the author believes that the method should have a brightfuture.