Mechanical and Chemical Effects of Pore Water on the Shear Strength of the Weathered Mudstone in Lanzhou City

摘要

The reduction of shear strength of saturated rock (soil) is the result of a series of complicated mechanical,physical and chemical functions between pore water and rock (soil).In this research,soil samples were collected from weathered mudstone near Wenchangge and Xujiashan landslide,and were saturated in solution with different concentration of calcium chloride and different pH,then direct shear tests were preformed.Combined with the physical properties,chemical constituents and clay mineral of the samples,a preliminary analysis was made about the mechanical function and chemical interaction mechanism between pore water and weathered mudstone.The results showed that,in the condition of fast shear,mechanical and chemical effects coexisted while mechanical effect was much stronger.The internal friction angle ((Φ)) increased slightly with a higher concentration of Ca2 +,while decreased with a higher pH.The trending was related to the clay mineral and soluble salt of the soils.The cohesion (c) didn't change regularly with the concentration or pH,which could be explained as in the condition of consolidated quick shear,mechanical effect was much stronger than chemical effect.