Laboratory Study on Shear Strength of Loess Joint

The internal friction angle of loess joint is measured by means of direct shear test. The results show that the relationship between internal friction angle and moisture content is revealed to be a parabola one. The internal friction angle has an extremum when the moisture content reaches a certain value. This moisture content is called the limit moisture content. The internal friction angle is also related to the dry density of loess, but it is not remarkable. The matric suction of the tested loess is tested as well. Analysis bases on tested data shows that, when the moisture content is greater than the limit moisture content, the matric suction and shear strength decrease with the increase in moisture content of loess. However, when the moisture content is lower than the limit moisture content, the current understanding on the relationship between water content and matrix suction is not appropriate, and results show that the matric suction and shear strength increase with the increase in loess moisture content.