Research On Stress Effect And Size Effect Of Shear Strength Based On Natural Three-dimensional Irregular Rock Structure Surface

A large number of practical projects have shown that the failure of rock mass is mainly caused by the failure of the rock mass structural plane.The shear behavior of rock mass structural plane,especially the stress effect and size effect of the structural plane shear strength,has a decisive influence on the physical and mechanical properties of the rock mass.In this regard,many scholars have also carried out a lot of research at home and abroad,but there are relatively few studies on three-dimensional irregular structural planes.Therefore,this paper focuses on the stress effect and size effect of the natural three-dimensional irregular rock mass structural plane.This paper combines three-dimensional scanning technology and 3D printing technology to produce structural plane panels that are consistent with the original rock structural plane.46 sets of structural plane model samples were made by the self-made integrated molds.The indoor direct shear test was carried out by the multi-functional geotechnical contact damage test system.The influence of normal stress,structural plane roughness and size on the peak shear strength and residual shear strength of the structural plane was analyzed.The main work and conclusions of this paper are as follows:1.Scanning the original rock surface with a MetraSCAN? handheld 3D laser scanner to obtain its surface morphology,and the structural plane panel was printed by a 3D printer.Three kinds of structural plane model samples of different sizes and roughness were produced by the self-developed integrated mold.2.It can be known from the structural plane failure mode test under different normal stresses: the climbing and the climbing and gnawing failure of the structural plane mainly occurs under the low normal stress,while the gnawing and the completely gnawing failure may occurs under the medium and high normal stress.3.By conducting direct shear tests on the three different roughness structural planes in the full stress range,it can be seen that the peak value and residual shear strength of structural plane with the same roughness increase with the increase of normal stress.In the low normal stress range,the peak and residual shear strength of the structural plane under the same normal stress increase with the increase of JRC value,but there is no obvious law within the high normal stress range.The peak shear displacement of structural plane increases with the increase of normal stress.4.Through the indoor direct shear test,combined with Photoshop software,the variationlaw of the shear surface area of the structural plane under different normal stresses is obtained,according to test results,shearing area of hanging wall of three structural planes is generally smaller than the shearing area of footwall,and proportion of shearing area increases with the increase of the normal stress.5.It can be seen that the size effect of shear strength of structural planes is not obvious by direct shear tests on three different sizes of structural planes with the same roughness under three different normal stress levels.