Influence of Gelling Time on Permeability and Strength of Ground Improved by Chemical Grouting Method

摘要

Since the 1995 Hyogoken-Nanbu earthquake caused serious damage,countermeasures against liquefaction for revetments have beenexecuted rapidly in Japan. A chemical grouting method has beenselected as one of them. One reason for this is that the method can beapplied without ceasing operation of improved facilities during theimprovement work because a set of grouting machines equipped forconducting the method is quite compact. Furthermore, this methodhas advantages of low vibration, low noise as well as less groundheaving during the construction.However, in case that an appropriate gelling time of the grout is notset, it is pointed out that construction defects such as poorly-lithifiedgrouting and fractured grouting may happen. It is, therefore,important to decide a proper gelling time for a type of soil at aconstruction site. Moreover, it is important to grasp how groutmaterial behaves in ground in order to improve the ground properly.In this paper, the effectiveness of the chemical grouting methodagainst liquefaction is proved from survey results on the Tohokuearthquake damages. And a series of grouting experiments, usingone-dimensional and two-dimensional containers, was conducted onmodel sand grounds grouted with various gelling times of groutmaterials. In the experiments, in order to examine the dilution ofgrout material, stereometry and strength test of the grouted specimen,measurement of distributions of silica concentration and pH in thegrouted material were conducted. As a result, it was confirmed thatthe infiltration behavior of the grout material could be visualizedusing the two-dimensional container, and the dilution of the groutmaterial was observed. In addition, the appropriate gelling time of asand specimen for the chemical grouting method was discussed.