Abstract
The dam foundation rock mass, at the Baihetan hydropower station on the Jinsha River, is mainly columnar jointed basalt, with faults and fissures developed. Considering adverse factors such as the unloading relaxation or the opening of the fissures due to excavation blasting, consolidation grouting is needed to improve the integrity of the dam foundation rock mass. According to the physical and mechanical properties of columnar jointed basalt and the continuity of construction, the effectiveness of overburden consolidation grouting is experimentally studied. The results show that this grouting technology can obviously improve the integrity and uniformity of a dam foundation rock mass and reduce the permeability of the rock mass. After grouting, the average increase in the wave velocity of the rock mass is 7.3%. The average improvement in the deformation modulus after grouting is 13.5%. After grouting, the permeability of 99% of the inspection holes in the Lugeon test section had Lugeon values of no more than 3 LU. This improvement is considerable and provides a case to engineering application.
Highlights
The safe operation of arch dam depends on the safety of dam foundation, dam structure, hydraulic device, and reservoir water environment
The Lugeon test was not performed on the 5 m protective layer of overburden
The Lugeon test calculation formula is shown in q where q is the permeability of the test section, Lu; Q is the pressure inflow, L/min; P is the total pressure acting on the test section, MPa; and L is the length of test section, m
Summary
The safe operation of arch dam depends on the safety of dam foundation, dam structure, hydraulic device, and reservoir water environment. Columnar joints and microfissures in fresh columnar jointed basalts are rigid structural surfaces, closed under confining pressure, easy to open, and relax after releasing confining pressure [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. It cannot meet the requirement of sufficient bearing capacity and stability of dam foundation rock mass as arch dam. In order to increase the deformation resistance of the foundation, improve the shear and seepage resistance of the structure surface, avoid the foundation surface bedrock unloading relaxation, reduce the impact of excavation blasting crack surface opening, and improve the integrity of the dam foundation rock mass, it is necessary to carry out consolidation grouting test for dam foundation, study and prove the feasibility and reliability of rock mass as the foundation of arch dam after grouting, and provide reference for reasonable design and determination of construction parameters of rock mass consolidation
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