Shear strengths of fissures in ledge rock before and after grouting

Abstract

In many hydraulic structures it is necessary to improve the physicomechanical properties of fissured ledge rock in the foundation. In practice, this is usually carried out by cement grouting, which aims at making the rock monolithic, strengthening it, and increasing its modulus of deformation [1]. The way in which cementation by grouting of ledge rock affects its deformability under compressive loads has been widely investigated in the USSR [2, 3] and abroad; however, the effect on the shear strength along fissures has so far been studied only in a few papers.At the Laboratory of Soil Mechanics of the Siberian Branch of the B. E. Vedeneev All-Union Scientific-Research Institute of Hydrotechnology (VNIIG), experiments in 1964(VNIIG), experiments in -1965 showed that cementation of cracks in ledge rocks markedly reduces the shear deformation; increase in the resistance to shear forces was not so marked. Thus shear deformations of a cemented fissured granite pillar, 8 x 12 m in plan, at the Krasnoyarsk hydroelectric station (experiments by D. D. Sapegin) were lower by a factor of 4.5-6 than the corresponding deformations of a noncemented pillar, but the increase in shear breaking strength was only 7 -1 0 % ( i n limiting equilibrium). Experiments on gneisses atthe Naglu hydroelectric station (experiments by R. A. Shiryaev) gave similar results: the increase in the limiting shear loads was only 3-10fie. On the other hand, there are indications in the literature [4] that cement grou ti~g of markedly fissured rocks increases the shear strength-however, no numetical values are given for this increase. "

Study on the settlement of large-span metro station’s baseplate caused by the tunnels newly built beneath it

“…Considering the influences caused by the excavation of the left and right tunnels, the following two reinforcement measures are suggested so as to lower the maximum settlement of station's baseplate: [28][29][30][31][32][33] 1. Before the excavation of the newly built tunnels, the outward soil surrounding the contour line of the tunnels within 2 m is pre-reinforced through deep-hole grouting.…”

Analysis of failure characteristics of grouting concretion body under the action of water-force coupling

“…As early as the 1980s, P. D. Evdokimov et al studied the influence of grouting on shear properties of fractured rock mass (Evdokimov et al, 1970). In the 1990s, Zhou et al (1993) strengthened and grouted the weakly weathered rock mass near the base surface during the construction of Ertan Arch Dam, and theoretically analyzed the mechanism of rock mass mechanical changes by fracture-damage mechanics method.…”