Experimental Research On Compound Grouting To Diabase Dikes Of The Arch Dam Foundation Treatment Works In Dagangshan Hydropower Station

Dagangshan hydropower station is a 210.0m concrete hyperbolic arch dam, there are more diabase dikes of poor distribution in the dam foundation and two sides that is the force transfer part, and affect the stability of the building. In order to effectively solve the problem of geological defects in diabase dikes, base on the pre-test results and the dikes characteristics, and select representative test area, taking the techniques of high-press cement and chemical grouting, and by the experiment studying the grouting plan,technological process,reinforcement effect,reinforcement mechanism and so on. During the experiment, in the rock-mass of test area, the high pressure cement grouting has been adopted firstly and then the chemical compound grouting is carried out. The material of cement slurry is ordinary portland cement,and the material of chemical grouting is epoxy resin with super consolidation performance,which belongs to the CW series. After the compound grouting, the entirety,continuity and sturdiness of rock mass in the test area are improved significantly, and the grouting effects are good.The main conclusions of the paper are as follows:(1) The technique of high-pressure cement and chemical compound grouting is necessary. Diabase overall was steep, which micro-cracks are developed and fracture aperture is small relatively, cement grout poured into the crack width of 0.2mm and it's below is difficult in the normal condition. In order to make full use of the true solution of chemical grout fill and cement grout the rock-mass part which the cement grout can't fill, taking the compound grouting plan that the high pressure cement grouting has been adopted firstly and then the chemical compound grouting is carried out, and study the reinforcement effect after the compound grouting.(2) Taking compound grouting reinforced the diabase is economical and feasible. Viewed from the different lithologies, the unit slug size of cement grout in diabase dikes is about 1/6 than in the granite, when the uniformity of rock-mass is relatively superior, taking chemical grouting not only ensure quality but also save materials, and epoxy grout can fill to the very fine cracks which is 0.01mm, and dense cementation. When the unit slug size is large difference between the diabase and granite which around the diabase, it is difficult to determine grouting effect for depending on the amount, should be combined with other means of detection of grouting effect, such as sonic testing or borehole elastic modulus testing methods.(3) The construction technology and the parameters of compound grouting are reasonable, which can directly guide the foundation treatment construction. In test, the distance between holes of cement grouting is 2.0m, and the distance between holes of chemical grouting is 1.4m, both constructions of them are divided into three sequences. The maximum target pressure of cement grouting is 5.0MPa, and the" hole-top-enclosed, top-down, sub-cycle" grouting technology is mainly used. For practical engineering application, should be increased both 5:1and 3:1 water-cement ratio and the effective injection of micro-cracks will be improved.The maximum target pressure of chemical grouting is 4.4MPa, and the" piecewise- obstruction, pure-compression style" grouting technology is mainly used, meanwhile, both "end under pressure" and " end of the quantitative perfusion " are used for grouting end standard .(4)The entirety,continuity and sturdiness of rock mass in the test area are improved significantly. After the compound grouting, sonic wave in diabase can reach 5184m/s, which increase 40.9%, in the granite can reach 5153m/s, which increase 13.4%, their cross-hole sonic can reach 4876m/s, which increase 14.4%, and the average pervious rate less than 1Lu, the rock-mass entirety is improved. The deformation modulus is in the range of 15.35–16.60GPa, and grout can fill to the very fine cracks which is 0.01mm, and dense cementation, the rock-mass continuity is improved. The average dry tensile strength of core is 5MPa, the average dry compressive strength is up to 75~90MPa or even higher, and the anti-shear is increased, the rock-mass sturdiness is improved.(5)The essence of the cement-chemical compound grouting for reinforcing the rock mass can be summarized as follows: after consolidation grouting, It is the fine filling and cementation of micro-cracks that reduce or eliminate the stress concentration on their ends intensively,and after force the failure mode from the compression - shear mode into pure-shear mode and its strength are enhanced. Meanwhile, the structural plane of rock mass and its disadvantage combination are improved, and form continuous and uniform structural body, and then partially restored stress and the anti deformation capacity is improved, so the strength and stiffness of rock-mass are increased after compound grouting, achieve the desired results.