锯齿状结构面力学效应实验研究

结构面在三度空间展布的形状称结构面形态。结构面形态是地质体发生变形和破坏后遗留下来的产物。在原位大型岩体力学实验中,结构面形态常常引起实验数据分散和产生不同的破坏机制;在岩体稳定性分析中,结构面形态又是影响结构面整体强度的重要方面,并涉及到工程岩体稳定性分析合理与否。因此有必要对结构面形态的力学效应进行研究。本文以锯齿状结构面为例,采用力学模型实验和理论相结合来讨论结构面的形态效应。

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF SERRATE STRUCTURE SURFACE

The experimental models are made from plaster of Paris. There are eight sets of models with sizes of (25 × 15 × 15) × 2 cm3. The up-slipping angles chosen for every model are 0°, 4°, 9°, 13°, 19°, 22.5°, 28°, 38° respectively, while the depression angles 0°, 15°, 45°, 40°, 18°, 20,° 34°, 15°.The model material (Rc) has a uniaxial compressive strength of 42kg/cm2, shear strength of φb = 45° and Cb = 6 kg/cm2, an elasticity constant (E) of 1.7× 104 kg/ cm2, and Poisson’s ratio of 0.225. According to the shear tests of serrate structure surface and the theoretical study, the following conclusions can be obtained :1. There are three types of shear resistance-displacement curves in the shear of serrate structure surface: (1) the curve of snip-off; (2) the curve both of up-slip and of snip-off after up-slipping; (3) the curve of up-slip.2. There are three failure mechanisms in shearing of serrate structure surface: (1) the up-slipping failure; (2) the snip-off failure after up-slipping; (3) the snip-off failure without up-slipping.3. The whole process of shearing from beginning of shear deformation to yielding residual strength has gone through three stages: (1) the shear deformation stage; (2) the shear fracture stage and (3) the stage of transformation of shear zone.4. The shear tests of serrate structure surface show that the frictional angle of serrate structure surface may be considered as φa = φj + a, where φj is frictional angle of straight structure surface, and a is up-slipping angle.5. The normal stress of critical snip-off (zzm) on experiments is in coincidence with the results of theoretical analysis. Thus,zzm=(Cb - Cj since (ctgα + ctgβ) (cosα -sinαtgφj)]-1)/(tg(φj+2)-tgφb)can be used as a criterion to correct the up-slipping angle in analysing the mechanical action on serrate structure surface. In the formula β is the depression angle, φb and Cb are parameters of shear strength of rock block.