Abstract: In-situ deformation test is an effective means of evaluating the grouting effect of rock mass as it acquires the deformation modulus of rock mass accurately. In the southwestern region of China where the mountains are high and steep and the terrain is dangerous, the complicated terrain and climatic conditions make it difficult to carry out in-situ deformation tests on slope surface. In view of this, we present a method of in-situ deformation test and measurement for high and steep slopes. We analyzed the influence of stress transmission depth on deformation test results, and proposed a calculation formula of deformation measurement error caused by changes in temperature. Take the high slope of a hydropower project as an example, we selected different rock masses with parallel structural planes and tested their deformation moduli before grouting, after grouting and after enhanced grouting. Our findings revealed that 1) consolidation grouting had no significant improving effect on the deformation modulus of high-quality rock mass, while the deformation modulus of low-quality rock mass increased by 22% and 38% after grouting and enhanced grouting, respectively; 2) filling and cementing the structural plane played a restraining role on the deformation of the rock mass on both sides, similar to the effect of increasing the intermediate principal stress on the deformation modulus; the deformation modulus of the rock mass along the direction of the structural plane will also be significantly improved.

Key words: rock mass, structural plane, grouting, deformation modulus, sonic velocity, high and steep slope