Study on quantitative evaluation of grouting effect by water pressure test

The permeability and mechanical strength of rock mass after grouting is an important parameter to reflect the grouting effect of rock mass. In order to quantitatively evaluate the effect of grouting water plugging project,taking the water plugging project of special large water inrush from Ordovician limestone of a mine in Anhui province as an exam- ple,this paper puts forward a method of high pressure borehole water pressure test to quantitatively evaluate the bloc- king source grouting effect of the Taiyuan formation limestone C53 . In view of the drastic change of rock mass permea- bility during high pressure water pressure test,the permeability coefficient of rock mass is calculated by the turbulent seepage law. The results show that the Taiyuan formation limestone C53 after grouting exhibits a good water resistance performance and the behavior of high water anti-pressure and low permeability. It means that the blocking source grou- ting has a good effect. The mechanical strength of rock mass to resist hydraulic fracturing can be judged by its critical impermeability strength. The calculated critical impermeability strength of the Taiyuan formation limestone C53 after grouting is 1. 83 MPa per meter. Based on the test principle of the energy dissipation test of water resistance coeffi- cient,the Taiyuan formation limestone C53 after grouting is enough to resist the splitting failure of Ordovician limestone water with 5. 64 MPa pressure,and it can eliminate the threat of water inrush from Ordovician limestone in the coal seam floor,as well as it can achieve the purpose of the blocking source grouting project.