Distribution Of Stresses On Bonded Length Of Rock-Socketed Anchoring Rods Under Pile Tip And Its Application

With the rapid development of our country's Civil Engineering, the requirements of the superstructure such as Long-span bridges to settlement and bearing capacity of the foundation are higher and higher, pile foundation has extensive application in engineering practices because of its much merit. The use of economic and reliable method to test the vertical bearing capacity of pile, is not only the requirement of existing criterions, but also the topic of important theoretical and practical significance in the area of pile foundation. Since the self-anchored loading test technology of pile foundation as a new application technology, there is a deficiency of systematic and thorough research on the distribution of stresses along the anchorage length of the anchoring bolt under pile toe. By integrating with the Construction Technology Projects of Hunan Province(NO.200403), this paper discussed the uplift mechanism of bolt, the distribution of stresses along the anchorage and its application. Mainly research and investigation are done as the following:Firstly, Through comprehensive analyses of the domestic and world related references and experimental data, an in-depth study and summarization of the anchor-soil load transfer behavior and the uplift mechanism of bolt is obtained, also, the influence of the form of anchorage section on anchoring force is discussed.Secondly, According to the structure and the mechanical characteristics of tension anchor, an analysis method can effectively reflect the working condition of rock-socketed anchoring bolt under pile toe in the system of vertical load-bearing capacity test of pile foundation by the self-anchored technique is proposed, and a new load transferring function suitable for anchoring bolt under pile toe are set up, on the basis of this new load transferring function, an analytical solution of the distribution of stresses along the anchorage length of tension anchor is obtained. Then, the distribution of stresses and the influencing factors are discussed in detail.Thirdly, According to the structure and the mechanical characteristics of the Pressure-type anchor, An analytical solution of the distribution of stresses along the anchorage length is obtained based on the Kelvin's elastic displacement solution and the dilatancy effect between anchorage-body and surrounding rock. Then, the distribution of stresses along the anchorage length and the influencing factors of the Pressure-type anchor are discussed in detail. Finally, Based on the analyses of linear deformation and the behaviors of anchorage body, the estimated formulas for critical anchorage length and ultimate bearing capacity of normal bolt are both derived. Moreover, Through comparing the theoretic calculated values with the experimental test results and specific examples of projects to verify rationality of the calculation formulas about critical anchorage length and ultimate bearing capacity of normal bolt.