Advance and review on grouting critical problems in fractured rock mass

A geotechnical engineering is prone to instability and failure under excavation unloading. The main reason is related to the expansion and transfixion of internal joints and fracture in rock mass. Grouting is the important means to repair fractured rock mass and improve surrounding rock stability according to the engineering practice. Systematic summary was made regarding the state of fractured rock mass grouting according to the available data，and the key conclusions were obtained：slurry transportation and diffusion law in fracture network have been obtained remarkable achievements during the last several decades，discrete fracture network theory has become the mainstream of research，and the essence of slurry flow in the fracture is the process of stress-seepage coupling dynamic response and feedback under multiphase flow；grouting achieve the purpose of cementation and strengthening through the induration formed by the slurry and the fractured rock mass, which significantly improve the physical and mechanical properties of the fractured rock mass, increase the overall strength；numerical simulation of grouting of fractured rock mass by discrete element method can better reflect the essence of slurry flow diffusion in the fracture. Research on grouting problem in fractured mass at present is far from mature at the same time. The existing theory lags behind the engineering practice, and a large number of scientific research achievements are difficult to turn into practical grouting engineering applications. Combined with the existing grouting theory in fractured rock mass，it is of great significance to use a reasonable numerical simulation method and simulation test to investigate the grouting critical problems in fractured rock mass and to guide the field grouting technology. The future studies are considered to be in the following four directions：① establishment of stress-seepage coupling control equation and numerical simulation realization of the dynamic process；② establishment of anchoring-grouting theory of fractured rock mass engineering；③ establishment of a theoretical system for grouting in deep fractured rock mass.