Volume 34, Issue 6 (November 2011)
New Three-Way Split Mold Design and Experimental Procedure for Testing Soft, Grouted Soils
Soil grouting has become a popular method for soil improvement in recent years. Grouting is generally intended to increase a soil’s strength, increase its liquefaction resistance, or reduce its hydraulic conductivity. Soil grouting involves the injection, permeation, or mechanical mixing of cementitious, silica, or clay grout into a soil deposit. With the increase in popularity of these methods comes the issue of testing grouted soils to verify the expected soil improvement. While some of the methods and materials mentioned result in soils that are sufficiently cemented to produce trimmable specimens that can stand under their own weight, other methods produce softer materials that are very difficult to sample or even to recreate and test in the lab. Preparing such soft samples in the laboratory poses two challenges: 1) if the specimen is prepared in the triaxial cell directly, the grouting process might not be feasible because of the porous stones and small diameter tubing in the triaxial cell; and 2) if the specimens are prepared outside the triaxial cell, soft specimens might not be able to stand under their own weight without significant strains and damage to the soil structure. This paper will thoroughly describe a three-way split mold specifically designed to accommodate the permeation and testing of soils that are too soft or too weak to be easily sampled or tested in the lab. A simple procedure outlining the use of this three-way split mold will also be described. Finally, the results from a series of consolidated undrained, monotonically loaded triaxial tests will be presented as an example of the split mold application. These tests utilized the new three-way split mold for sample preparation of loose Ottawa sand permeated with a thixotropic bentonite suspension.