LAOLUE CHERXIONG

Experimental Observation of Tensile Failure Characteristics of Cement-Treated Sand

Hirofumi TOYOTA 

In this study, a new tensile stress intensity testing method was established to evaluate the propagation of tensile cracks in sandy ground, using cement-treated sand that simulates undisturbed in-situ samples. First, tensile stress intensity tests were conducted using three types of specimens with different end conditions to examine test stability and the feasibility of evaluating tensile crack propagation. The results revealed that specimens without end treatment and those treated with silicone rubber were unsuitable for stable tensile testing due to air leakage and insufficient adhesion at the boundaries. In contrast, specimens treated with clay at the ends successfully suppressed air leakage and enabled continuous measurement of stress intensity up to just before the onset of tensile cracking, confirming the applicability of the proposed method for sandy ground.

Next, the effect of cement content was examined. At low contents (0.7–0.8%), the tensile stress intensity was too small to evaluate crack propagation. At 1.6% or higher, failure occurred at the sand–clay interface, preventing measurement at the specimen center. Therefore, under the conditions of this study, a cement content of 1.0–1.5% was found to enable stable tensile stress intensity testing.

Furthermore, compression strength tests were conducted to evaluate the mechanical properties of cement-treated sand. The compressive strength was about 3.7 times higher than the tensile stress intensity, indicating relative weakness in tension. Compared with clay specimens of similar tensile stress intensity, clay showed ductile failure, whereas cement-treated sand exhibited elastic behavior followed by sudden brittle failure. These results emphasize the need to consider both tensile stress intensity and failure characteristics when assessing tensile crack propagation.