Search

Aiming at the problem that the swelling force of the red-bed mudstone is smaller than the theoretical value according to the code, this paper develops a triaxial swelling force device for the swelling rock. By placing the sample first and then restraining it, the deformation gap between the rock and the container’s wall is overcome. Through the experimental research of the triaxial expansion force of expansive soil and red-bed mudstone, the rationality and effectiveness of the triaxial expansion force device are verified. According to the experimental test results of the typical red-bed mudstone samples in Sichuan, the changes of the swelling force of the muddy swelling rock is preliminarily summarized. The research results show that the triaxial expansion force device and its test method can overcome the limitations of the existing method of consolidation instrument test. It is simple to operate, is of good practicability, and can be applied to the triaxial expansion force test of expansive soil and expansive rock. The experimental results of comparison of triaxial expansion force and uniaxial expansion force show that the triaxial expansion force of the red-bed mudstone is mostly in the magnitude of MPa, and the expansion force tested by the consolidation instrument is mostly in the magnitude of kPa. Through the analysis of the test results and the observation of the sample after expansion, it is found that the expansion mechanism of the red-bed mudstone is different from that of the expansive soil. The red-bed mudstone is mainly the surface layer of fresh rock that absorbs water and swells and disintegrates. After the surface layer is denuded, the fresh surface absorbs water again to swell and disintegrate. This is a cyclic expansion process layer by layer.

The thickness of hydration film of clay particles is the theoretical basis of swelling mechanism of argillaceous expansive rock and soil. There are abundant data on the measurement of clay particle hydration film thickness, but the study of the measurement of clay particle hydration film thickness by atomic force microscopy is relatively rare, and the test method is not perfect. Based on the three-layer hydration membrane structure model and atomic force microscope test technology, through the test and research on montmorillonite powder, mudstone powder and mudstone rock slice, this paper puts forward the measurement method of the thickness of the hydration film, the preparation method of powder sample and rock sample, and the statistical processing method of the test data. The variation rules of the free water section, weakly bound water section, strong bound water section and clay particle section of the hydration film thickness test curve are summarized. Through comparative analyses with the existing research results, the rationality and feasibility of the testing the thickness of the hydration film of clay particles by the atomic force microscope is demonstrated. Combined with engineering practice, the engineering significance and theoretical value of the quantitatively obtaining the hydration film thickness in understanding the swelling mechanism of the argillaceous expansive rock and soil are discussed.