Experimental study on expansion mechanism and characteristics of expansive grout

Abstract

Aiming to address the problem of traditional grouting reinforcement of jointed rock mass only providing bonding force to the joint surface, the grouting reinforcement technology of expansive grout was proposed. This technology generates compression force through the volume expansion of the grout itself, leading to a reinforcement idea of “first squeezing and then bonding” to increase the overall strength of the jointed rock mass. To solve the problem of the preparation of expansive grout materials, an expansive grout proportion test using high efficiency soundless crush agent (HSCA) as the expansion source and cement as the cementing material was performed. Considering the single free surface expansion rate (SFSER) and lateral expansion pressure (LEP) of expansive grout specimens as the investigated indices, the expansion evolution law of expansive grout and the effect of cement content and expansion agent content on its expansion characteristics were explored from both macro and micro level. The experimental results show that: (1) The expansion evolution processes of expansive grout after final setting can be divided into four phases viz. rapid expansion period, slow expansion period, residual expansion period and stable period. After 120 h of final setting, the grout expansion basically ended. (2) the expansive grout with different cement contents could produce SFSER between 0.83% and 18.54% and LEP between 0.08 MPa and 1.83 MPa when the content of the expansion agent was 3–12%. (3) The effects of the expansion agent content on the SFSER and LEP of the expansion agent were similar, and they all showed an S-shaped curve with increase in the expansion agent content. The experimental results provide a significant understanding of the expansion mechanism and characteristics of expansive grout.