Experimental study of compressibility of red clay affected by acid-base and soluble salt solutions

Guilin is located in the southwest of NE-SW trend Xiang-Gui lowland corridor with coordinates of longitude 110°17′and latitude 25°14′. It has a subtropical monsoon climate with abundant annual rainfall, and is hot, humid and rainy. Guilin is in the Lijiang River valley plain, which has well-developed karst and large areas of red clay. The engineering properties of red clay in Guilin are very complex, making the water stability poor. The chemical activity is closely related with the chemical composition of groundwater. To study the effects of the water environment on engineering geological properties, the red clay was taken from a typical karst area in Guilin. The samples were soaked in different concentration solutions of HCl, NaOH, Fe(NO3)3 and Al(NO3)3. Experimental results showed that:(1) The compression modulus of the red clay decreased and the compression coefficient increased when it was soaked in different concentration of HCl and NaOH solution, and that the greater the solution concentration was, the larger the decrease in range would be; (2) The compression modulus of the red clay was greater when the red clay was soaked in a solution of NaOH than that soaked in a solution of HCl, and the compression modulus value decreased with the increase of solution concentration, the opposite of the compression coefficient; (3) The compression modulus of the red clay increased and the compression coefficient decreased with the increase of solution concentration when the red clay was soaked in solutions of Fe(NO3)3 and Al(NO3)3,and the effect of the Fe(NO3)3 solution was greater than that of the Al(NO3)3 solution.