Experimental Study Of Constitutive Of Soil Anchor Based On Digital Speckle Correlation Method

In order to realize the visualization of the deformation of anchoring interface,the paper reveals the mechanism of stress transfer in the anchoring body of the soil layer,and develops a kind of experimental apparatus for the interfacial mechanics characteristics of the semicircular cylindrical anchor body,which can simulate the axial symmetry of the anchoring body of the soil. Using two-dimensional digital speckle correlation method, the distribution regularity of displacement field and strain field of anchorage body and surrounding soil is obtained,and the formation,penetration and evolution characteristics of shear bands around the Anchorage body are revealed with the increase of the displacement of anchoring body.The experimental results show that the displacement of the anchoring body leads to the deformation of the surrounding soils in a small thin layer near the anchoring body. The deformation of this layer of soil has a small range,continuous deformation, roughly linear distribution. With the increase of the displacement of anchoring body, the shear strain bands of the soil surrounding the anchoring body are the process of the local, scattered area to the mutual connection and through. In this shear strain belt,the maximum shear strain is large,symmetrical distribution along radial, and has remarkable shear-swell effect. This experiment provides a new method for visualization experiment of axisymmetric problem in geotechnical engineering. The displacement and strain characteristics of the soil surrounding the anchorage body obtained by the experiment provide the basis for the study of the mechanism of the anchoring load transfer, the establishment of interface constitutive relation of Anchorage body and the construction of interface element in numerical simulation. The main findings and innovations are as follows:(1) This experiment adopts the semi cylindrical anchoring body interface which is loaded by using the tester, the equipment is simple and easy to operate, which can not only reflect the axial symmetry characteristics of anchoring body and surrounding soil, but also realizes the visualization of the deformation of the anchor solid and soil interface in the experiment, and achieves the anticipated goal, which provides a method for the geotechnical mechanics experiment.(2) This experiment uses two-dimensional digital speckle correlation measurement system to carry on the experiment of the interfacial mechanics characteristic of the soil anchoring body, the displacement and strain image of the Earth body surrounding the anchoring body is obtained by the image processing software and the rendering software, which can satisfy the requirement of the analysis of the experiment results by the visual,flexible and full-field characteristics.(3) With the increase of the displacement of anchoring body, the anchoring body leads to the axial displacement of the surrounding soil. The displacement is continuously distributed along the radial direction, and there is no "slip" phenomenon.The axial displacement of the soil in the vicinity of anchoring body is a small part of the main anchoring body (< 10mm) and is linearly distributed, whereas the displacement of the outside part is negligible.(4) The load transfer and deformation process of the anchoring body of soil layer is actually the process of forming the shear strain zone around the anchoring body. With the increase of the displacement of the anchoring body, the shear strain area is enlarged by the initial local, dispersed, uneven and gradually along the anchoring body axial, interconnected and finally connected, forming a complete shear slip belt. The shear strain zone is located outside the surface of the anchorage body, with the characteristics of small width, large strain and large strain distribution.(5) The shear strain bands around the anchorage body have remarkable shear-swelling characteristics, which are verified by radial earth pressure sensors and radial displacements. The radial pressure generated by shear strain band is characterized by the linear growth of the displacement of anchoring body, and the constant, which can not continue to increase, is similar to the load displacement curve of anchoring body.The displacement and strain regularity of the soil surrounding the Anchorage body obtained in this paper is a reference for studying the load transfer regularity of the anchoring body, establishing the interface constitutive relation of anchoring body and constructing the interface element in numerical simulation.