A Comprehensive Classification Method for the Pore Permeability of Deep-Mine Sandstone Used to Guide Grouting

Abstract

One type of seepage water that is difficult to plug by grouting is the water exuding through the pores of sandstone in deep underground engineering. Aiming at this problem, this paper collected deep-mine sandstone samples from the Southwest Shandong coalfield, studied the sandstone pore structure and its influential factors by casting thin slices, scanning electron microscopy, mercury intrusion and physical property tests, and selected five representative permeability classification indicators: permeability, porosity, average pore throat radius, comprehensive diagenetic coefficient and sorting coefficient. According to these five indicators, the pore permeability of all the sandstone samples was divided into four subcategories (I1, I2, II1, and II2) from the perspective of grouting. I1 has medium pores and medium pore throats that can be filled with ultrafine cement-based slurries; I2 has medium-small pores and fine pore throats; II1 has medium-small pores and fine pore throats or small pores and microthroats; both I2 and II1 can be filled with chemical slurries; and II2 has micropores and microthroats that cannot be grouted. This case study provides a reference for the classification and evaluation of the pore permeability of sandstone for grouting and lays a foundation for classified permeation grouting and subsequent pore-expanding permeation grouting.