Test Approach For Anchor-soil Interface And Nonlinear Loading-deformation Analysis Of Anchor

With the continuation of national large-scale infrastructure construction and the need of Chinese construction industry integrating to international market, the development of anchorage engineering changes with each passing day and the research of loading-deformation characteristics of anchors will carry out from beginning to end. However, theoretical research on anchor of the current stage is far from satisfaction, the corresponding analysis methods is not quite consistent with the actual situation which brings certain difficulty to the engineering design and construction. Therefore, with the support of the National Natural Science Foundation of the Water stability and time-varying reliability analysis of soil slope anchorage system of residual soil slope(50878082) this thesis conducted some systematic and in-depth research on anchor soil interface performance test method and the nonlinear loading-deformation characteristics of anchor in order to provide some guidance and help for the relevant theoretical analysis and engineering construction.Firstly, with the shortage of specialized anchor soil interface performance test device and the corresponding method, a whole series of anchorage interface shearing test equipment was designed based on infinitesimal element force analysis, including compaction, sample preparation and pulling out process etc. Four groups of pull-out tests were completed on this testing system. Test results indicate that the feasibility and reliability of the anchoring-soil interface performance for the equipment. The relationship between the interfacial peak shear strength and interfacial shear rate and that between the interfacial pear shear strength and the curing time for the anchoring body. Besides, three types of τ-s constitutive models were simulated based on test results.Secondly, considering the influence of different water content and different soaking time, tri-axial compression tests of colluvial soil were carried out, using the Kriging prediction model to interpolate the stress-strain curve of tri-axial compression and then the anchor soil interface shear tests under different water content were implemented. Accordingly, the regression analysis for the relationship between the interface peak shear strength and water content were carried out. Finally, based on the uniform experimental design method, considering the influence of these two factors the soil moisture content and dry density on the peak shear strength of the interface size, the relationship between the interfacial peak shear strength and water content as well as that of the interfacial peak shear strength and dry density were established respectively on the basis of Kriging prediction method and regression analysis method.Thirdly, the laboratory large scale model test were carried out, through pulling out under varied loading modes and different constraints on 3 model anchor bars. Thus, the corresponding loading-displacement curves were obtained, the similarities and differences among the load-displacement curves of the three bolts were discussed, and the in-depth analysis of different loading modes and different constraint conditions under the axial force of the bolt and shear stress along the length direction of the bolt distribution were carried out. Attention on declined pull-out load when isokinetic drawing the bolt in engineering application should be strengthened.Then, combined with the simple nonlinear interface model and considering the residual strength of nonlinear interface model, based on load transfer method and introduce the power series approach, this thesis concluded the semi analytical solution for the distribution of the displacement of the anchor along full-length, axial force and shear stress and the reliability and rationality of the theoretical derivation was verified through an example. Meanwhile, the influence of several influence factors such as the peak location of interface model, anchor solid modulus, the anchorage length and interfacial residual strength of anchor, etc. on loading-deformation characteristics of anchor rods was discussed.In the final place, this thesis introduced 4 different interface models. In the meantime, based on the load transfer method and transfer matrix method, the stress and deformation calculation of the bolt on the layered soil were analyzed and the expressions of the displacement, axial force and shear stress of the anchor in different soil layers under different stress stages were derived. Then, the feasibility of the methods was verified through engineering examples. On the basis of the shear displacement method, considering the reinforcement effect of grouting and other factors on the surrounding soil and the resulting increase of shear modulus, the improved shear modulus was assumed to decrease with the linear, parabolic and exponential distribution types to the shear modulus of soil under natural conditions. Consequentially, the shear moduli under different distribution of stress deformation changes along the radial direction were discussed. The results indicated that the displacement of anchor head decreased with the increase of the shear modulus increase.