ABSTRACT:

Micro fissure grouting is often applied to improve the quality of the surrounding rockmass in underground engineering. While it usually does not work in field because the cement is difficult to be injected into the rock fissure and the cement particles cannot consolidate quickly, therefore it cannot effectively strengthen the rockmass. A new grouting method DGT (Derive Grouting Technology) was presented in this paper to solve these problems. In this method, special cement with high flowability and strength in early age was developed and used as grouting material, and expelling holes were drilled around the grouting hole according to the fissures distribution to derive water out of the micro fissure and leave the cement particles inside. By controlling certain grouting pressure, the cement particles in the micro fissure accumulated and solidified quickly and the quality of rockmass could be improved in a short time, which was very important for deformation controlling of the surrounding rockmass in excavation process. In addition, acoustic testing proved the validity of the technology in an underground project.

1 INTRODUCTION

Grouting is also called injection grout (Kuang, 2001), which is used for enhancing the impermeability and anti-seismicity of the grouting area. The purpose of the grouting with pressure is to fill the joints, discontinuities, void distance and cavities in the rock masses to consolidate and caulk the rock masses for reducing seepage and uplift pressure in dam foundation and related structures (Zadhesh 2014). By applying an appropriate pressure, grouting material which is of flowability in early age and adhesion before solidification was injected into the necessary position, thus the stability and safety of the structure could be improved. The grouting area are mainly soil mass and rock mass (Hao 2001). Grouting materials often include dissolvable materials and suspended materials. Dissolvable materials are mainly made up of chemical materials while suspended materials are mainly cement materials. Grouting projects often use clay, pozzolans and calces as grouting materials formerly. When Portland cement appeared in 1826, cement materials were widely used in projects (Wang 2000). When admixtures like clay, bentonite, water glass, fly ash and pozzolans were added in the Portland cement, some characters were improved (Luo 2006). By now cement grouting is usually used as one of the most important techniques for soil and rock stabilization structures (Camberfort 1967).

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