Study On Grouting Technique For Directional (Guided) Drilling In Sand Gravel Stratum

Sand gravel, which is very wide distribution in our country. Because of the shallow burial depth, it is a more complex stratum in construction. That improving engineering mechanical properties of sand gravel is a important manner to solve the difficulty in the stratum. Being the porosity of the granular and less cohensive force between particles, sand gravel is a typical mechanical unstable sratum. The hole wall is easy to collapse in the process or reaming in this sratum. Hole wall collapsing causes that the drilling and reaming construction is difficult, which is a problem of trenchless construction long. Therefore that solving the unstability of hole wall is the key to slove the difficulty of trenchless construction in sand gravel.Through the literature inspection, that the characteristics of sand gravel and difficult in directional(guided) drilling are summarized. Based on the laboratory test, that the rheological properties of cement and physical properties of slurry are studied. The permeability formula and hole wall stability are studied. Engineering example is simulation analyzed.In the base of analysis of characteristics of gravel stratum and engineering experience summary, the reasons of difficulties of directional drilling and unstability mode are obtained; strengthening methods are proposed. Fitting analysis of the test data through origin, the results show that the viscosity of cement grout changes with time. By testing the physical properties of the slurry, that the gel time and compressive strength of grout will be growth and decrease with increasing amounts of sodium silicate are obtained when the incorporation of Sodium silicate above a certain value. A permeability formula of cement slurry is deduced, in which the viscosity changes with time. According to analysis of the diffusion form of horizontal grouting, that the diffusion form of the horizontal grouting is obtained. Through the hole wall stability analysis, that the damaged location of hole wall, failure modes and requirements of grouting to ensure the stability of hole wall in different conditions are getted. Based on the analysis of the actual project, that the pre-reinforcement of grouting is possible to solve unstability of the drilling hole wall is proved.