Research On The Force Transmission Mechanism And Uplift Performance Of The Fully Grouted Anchorage System Under Pullout Load

In recent years,geotechnical anchoring technology has developed rapidly and is widely used in reinforcement engineering such as civil engineering and mining.Three main types of anchoring technology are widely used at present: mechanical anchoring,grouting,and friction anchoring.Among these,grouting anchoring is the most popular in practice due to its ease of installation,relatively low cost,and versatility in applications.Among the various types of anchors,fully grouted anchors are the most common in practical applications.In order to fully reveal the bearing characteristics of the fully grouted anchorage system and provide a basis for the optimal design and construction of geotechnical anchorage projects,this thesis conducts a systematic study on the force transmission mechanism and uplift performance of the fully grouted anchorage system under pullout load by comprehensive use of on-site experiments,numerical simulations,theoretical analysis,and mathematical statistics.The research work is carried out from six aspects: on-site large-scale full-scale experimental research,simulation of progressive failure process and analysis of influencing factors,research on the transmission law of pullout load,back analysis of force transfer mechanism based on load-displacement curve,impact analysis of mechanical properties of rock and soil,and impact analysis of loading process.The main research works and innovation achievements of this thesis are as follows:(1)A large-scale comprehensive on-site full-scale testing platform for grouted anchorage systems has been established,which can simultaneously complete on-site tests of multiple methods,purposes,and types of grouted anchorage systems.The results of different pullout tests can be compared and analyzed horizontally and vertically.Based on the pullout test data of the testing platform,the load-displacement curve characteristics,bearing performance,and failure mode of the fully grouted test anchor cable were analyzed,and some beneficial insights were obtained from the macro research perspective,providing a data foundation and guidance for the research work in other chapters of this article.(2)From the perspective of microscopic research,a calculation and analysis model for the fully grouted anchorage system was established using PFC5.0 software.The progressive failure process under tensile load was analyzed from five aspects:displacement,stress,crack propagation,structural changes,and energy analysis.Based on the purpose of economy and energy conservation,the concepts of ultimate pullout force per unit volume and optimal slenderness ratio were proposed,and the impact of slenderness ratio on the fully grouted anchorage system was innovatively studied.A numerical model for the local void at the anchorage interface was established,and the impact of the local void at the anchorage interface on the load-bearing performance of the fully grouted anchorage system was systematically studied.(3)Based on the idea of discretization,the spring element method is introduced into the mechanical analysis of the anchorage system,and the relationship between the displacement distribution function,the axial force distribution function and the lateral resistance distribution function is established.Through the analysis of the mechanical behaviour of the anchorage interface,five linear load transfer models were created: the slider model,the spring model,the modified spring model,the spring-pulled slider model and the spring-slider model.After considering the interface softening characteristics,two softening models were established,namely the linear softening model and the exponential curve softening model.The applicability of each model and the impact of key parameters were analyzed and discussed,providing reference and guidance for the diversified analysis of load transfer in anchorage systems and the selection of load transfer models.(4)Considering the nonlinear characteristics of the shear slip at the anchorage interface,a double exponential curve load transfer model is established based on the exponential function of the anchor load and displacement.Based on this model,the pullout load transfer solution of the anchor is established,and the characteristics of the shear slip interface,the load transfer process of the pullout load,the load-displacement curve characteristics of the tension end and the influence of the key parameters are analyzed and discussed with examples,and some important conclusions are drawn from the perspective of theoretical analysis.Through on-site pullout tests,it has been verified that this model can effectively simulate the entire load transfer process of the fully grouted anchorage system under pullout loads.(5)From the two aspects of " Mechanical Behavior Analysis of Anchor in Soft and Hard Alternate Strata" and "Mechanical Behavior Analysis of Anchor Considering the Change of Mechanical Characteristics of Anchorage Interface with Depth",the influence of the mechanical properties of rock and soil on the pullout mechanical behaviour of the vertical grouted anchorage system was systematically studied,and some important conclusions were drawn.In terms of "Mechanical Behavior Analysis of Anchor in Soft and Hard Alternate Strata",the pullout load transfer solution of the anchorage system in the upper and lower parallel strata and the interlayer foundation was constructed,and the influence of changes of parameters such as stratum shear modulus and stratum interface depth on the pullout mechanical behaviour of the anchorage system was discussed by the numerical example.In terms of "Mechanical Behavior Analysis of Anchor Considering the Change of Mechanical Characteristics of Anchorage Interface with Depth",assuming that the mechanical properties of anchorage interface change with depth by exponential function and by linear function respectively,the pullout load transfer solution of the anchorage system in the two cases is constructed,and the test cases are used for verification and discussion respectively.(6)Based on the results of on-site large-scale full-scale tests,a horizontal and vertical comparative analysis was conducted on the test results of different pullout tests,and the relationship between the loading history parameters such as number of tests,test duration,and number cycles and the uplift performance of the fully grouted anchorage system was explored.Analyzed the changes in the pullout stiffness,shear modulus of the grout,and internal energy of the fully grouted anchorage system during the pullout process.The relationship between the pullout stiffness of the anchorage system and the shear stiffness of the anchorage interface was established.Based on the inference of the continuous deterioration of the shear stiffness of the anchorage interface,the cyclic loading and unloading process of the fully grouted anchorage system was simulated.There are 177 figures,20 tables and 200 references.