Design Of Anchor And Its Application Based On Mindlin Displacement Solution

Anchor was widely applied in the field of excavation,slope and underground engineering.Whether the bolt design reasonable can directly affects the quality,safety and economy,of the project.Since the geotechnical conditions for anchor application in recent years have "keep deepening" and "extremely complicated surrounding" main features,the accident caused by the failure of the anchor bolt has an increasing tendency.The dissertation mainly studies the design method on the four kinds of anchor from aspects of anti-pull force,anchorage length and anchor head displacement.And combined with engineering examples,the application was compared with the design results of standard recommendation methods.The dissertation mainly chooses the anchors such as tensile anchorage,tensile-dispersed anchorage,compression anchorage,compression-dispersed anchorage as the research object,the design method of anchor was studied as follows based on the Mindlin's displacement solution.(1)The anti-pull force of anchor was deduced from the condition that the peak of shear stress on the surface of the anchor meets the coulomb resistance.(2)According to the axial force distribution of anchor,two types of length of anchor were defined,and two types of length were deduced.(3)From the deformation of anchors proceed to derive anchorage displacement,and analysis of the anchorage stiffness coefficient.(4)From the perspective of elasticity and functional principle,the dilatancy of soil was discussed and the coefficient of dilatancy effect was obtained.(5)Through the application of engineering examples,the theoretical results were compared with the normative design to analyze,evaluate and discuss the rationality and reliability of the theoretical results.Through the research of the paper,the main results were summarized as follows:(1)From the calculation formula of anchor resistance,the anti-pull force was proportional to the shear strength and the square of anchorage diameter,but the ratio of elastic modulus to soil-anchor was inverse proportion,and the influence of anchor solid diameter on anti-pull force was the most significant.(2)From the calculation formula of anchorage length,the anchorage length was proportional to the diameter of anchor solid,and was inverse proportional to the ratio of elastic modulus of soil-anchor.(3)From the calculation formula of anchor head displacement,the greater the diameter of anchorage and the greater the product of elastic modulus of soil-anchor,the greater the stiffness of anchor.(4)From the formula of shear dilatancy effect coefficient,we can get that the influence of soil dilatancy on anchorage was related to dilatancy angle.The coefficient of dilatancy effect was smaller in the range of 5 degrees of dilatancy angle.Generally speaking,the influence of dilatancy effect on anti-pull force can be ignored.(5)Through comparison with examples,the calculated results of anchor pulling resistance in different soil layers were different from those calculated by standard method.The calculation results in cohesive soil were ideal,the results in sand layer were small,and the calculated results in weathered rock were large.The theoretical formula was in good agreement with the calculation of the anchorage length and stiffness coefficient.