Strengthening effect of sulphoaluminate cementitious grouting material for water-bearing broken rocky stratum

Abstract

A rapid-hardening sulphoaluminate cementitious grouting material (SCGM) is improved for water-bearing broken rocky stratum. Hydroxy propyl methyl cellulose (HPMC) and polycarboxylate-based superplasticizer (PCE) are used to improve fresh-state performance. Main diffusion ability, fresh-state properties, basic mechanical strengths, microstructure, etc., are investigated. A novel grouting simulation apparatus is designed to assess grouting effectiveness, the holistic reinforcement effect, compressive strength and anti-permeability of grouted specimen, typical failure mode, influence of key parameter and bonding characteristic of grout-rock interface are studied. The combination of 0.4 % PCE and 0.02 % HPMC can be applied at water-binder ratio (w/b) of 0.65–1.0. The maximal 3 d and 28 d unconfined compressive strength (UCS) of SCGM are 15.87 and 18.60 MPa, its 28 d UCS of grouted specimen can attain 14.98 MPa. The SCGM is eligible for rapid water blocking and effective reinforcement especially in water-rich and broken rocky strata. Based on the Coulomb failure criterion, relationships among UCS, internal friction coefficient and cohesion of reinforced rock were derived. Based on the linear relationship between internal friction angle (φ) or cohesion (C) and volumetric block proportion (VBP), the quantitative expression with UCS and VBP was established. In comparision with experimental data, feasibility of the quantitative formula in predicting UCS of reinforced rock is proved.