The Experiment-Study Of High-pressure Grouting On Carst Region

The rock mass is made up with rock and cracks, however, in the Carst region' s the rock mass also include the hole and cave develop for corrosion. Generally, the rock is impermeable, and the permeability of the rock mass depends on the permeability of cracks. Boring, grouting and finally forming an impervious curtain in the rock mass with cracks, that is one of the most popular methods of the foundation seepage control at hydraulic and hydroelectric engineering.Since first used in the WuJiangDu Hydraulic power station with success, high-pressure grouting (orifice-closed grouting method) spreads rapidly in the Carst region and lots of experience are accumulated. However, the geologic structure of the Carstic formation is complicated and the design, construction, quality testing method of the high-pressure grouting is developing rapidly. We have engaged lots of experiments and studies in XiangShuiRiver Reservoir on this subject. One of the purposes subject is to guide the design, construction of the curtain grouting in the XiangShuiRiver Reservoir and optimize the grouting Design, the other is to be a reference example for other similar engineering. The main points of this topic as follows:1. Review the changing at home and abroad of the reservoir' s seepage control on the Carst region.2. Adopt varied exploration method to check up on geologic structure of the all demonstration area.3. The Carstic formation is permeable layer and has quite good placeability, its relations of the water permeabitity and placeability have three types as follows:High unit-absorption rate with big grout consumption, the grouting is necessary; low unit-absorption rate with little grout consumption, the grouting is no need; Low unit-absorption rate with big grout consumption, grouting is no need combining with control the grouting pressure and grout consumption.4. Bring forward a improved orifice-closed grouting method (depths orifice-closed grouting method) due to broken rock on theearth' s surface.5. There are 979.32 meter long to the curtain of the XiangShuiRiver Reservoir include 879.32 meter' s long double row curtain (about 92 percent) in the original design. By optimizing the design according to the grouting test, the double row curtain was cut down to 245.66 meter length (25 per cent of them), The density of the bore hole have from 0.81m/m2 reduced to 0.64m/m2.Total save 4.47 million RMB cost of the project.6. The distance of the single-row curtain grout hole is between 1.4 to 1.8 meter, and 2.0 meter is suitable for the double-row curtain; the grouting pressure generally is 1.0 to 1.5 MPa at the first three grout compartment, then grouting pressure of under the fourth controlin 4 to 5 MPa; For mast grout compartments, a water-cement ratio of 2 or 1 may used in the first grouting.7. There obvious dependency relation between the unit-absorption rate and grout consumption, general there are bearing relation, but no obvious dependency relation between the index of the rock mass integrity and grout consumption.8. When using the index of the rock mass integrity, the index of the grouted rock mass integrity has raised one rank according to the theory and stand raised by this article.9. When grouting gallery of depth-curtain, lining and consolidation grouting to full-face of the gallery is necessary to meet the needs of the grouting pressure. But in the condition that the gallery base plate is the head of the curtain, and bare rock mass was stable enough then only lining to the gallery' s base plate is necessary. And the needs of the high-pressure grouting are satisfied. Thus large cost of the lining and consolidation grouting can be saved.