Mechanism And Experiment Research On The Interaction Of Anchor And Expansive Soil

The rock-soil anchoring technique is widely used and the load transfermechanism of anchor in expansive soil becomes complicated due to the swellingcharacteristics of expansive soil. The swelling-characteristic of expansive soil, thedeformation properties of anchor rod-expansive soil interface and the mechanicalcharacteristics of anchor after completion of expansion were researched based on tests.A theoretical calculation method for the load transfer mechanism of anchorconsidering expansion and tension action has been developed. This thesis isconcerned with the following aspects:(1) According to the test scheme arranged by orthogonal experimental design, theinfluence factors of swelling ratio, swelling force and the swelling deformationproperties were researched by laboratory soil tests. The change law of swelling ratiowith initial dry density, initial moisture content and overburden pressure, as well asswelling force with initial dry density, initial moisture content and allowabledisplacement, and the time curve of expansion were obtained. Then the empiricalformula of the no-load swelling ratio regarding initial dry density and initial moisturecontent, the loaded swelling ratio regarding initial dry density, initial moisture contentand overburden pressure, and the swelling force regarding initial dry density, initialmoisture content and allowable displacement are proposed.(2) The deformation properties of anchor rod-expansive soil interface wasstudied by the anchor-expansive soil interface model test based on the tester for thefriction properties of anchor rod-soil interface, which developed independently by theresearch team. Hence the shear stress displacement curve and the relationship betweenthe peak strength and saturation were obtained. Then it is put forward that the shearstress displacement curve of anchor-expansive soil interface accords with the tri linearsoftening model.(3) In order to study the properties of swelling deformation and the anchor’smechanical characteristics, the model device for anchor-expansive immersion anddrawing was designed and made. The curve of swelling capacity and depth, swellingcapacity and time, and the P-s curve of anchor after completion of expansion wereattained. Then the fitting formula describing the expansive deformation process ofexpansive soil and a method for calculating the swelling deformation of different depth are presented.(4) Based on load transfer method, the load transfer model of anchor consideringthe interaction of swelling of expansive soil and the pull-out load applied wereestablished. The load transfer governing differential equations of anchor were derived.Finally the analytical solution during elastic stage and the numerical solution duringelastic-plastic stage for calculating the displacement, the anxial force and shear on theanchor-expansive soil interface are obtained. The results of the model test verify thatthe theoretical calculation method is fessible. Meanwhile, the following influentialfactors on the load transfer characteristic of the anchor were studied, which inclu desthe heave of the ground surface, active depth, diameter and elastic modulus of anchor.