Study Of Moistening And Wetting-drying Experiment Of Coarse-grained Weak Rock

In order to investigate the deformation characteristics and microscopic mechanism of coarse-grained weak rock under different moistened water content condition and the wetting-drying test, this thesis puts forward a test method using iron wire mesh as outer boundary and a humidification way by steaming, which solves the problem that the conventional cylindrical rubber pockets can't carry on dehumidification and realize the process that the moisture content of the test sample gets from dry to wet and then to saturate.Main tests carried for coarse-grained weak rock in this paper are organized as follows: dampening tests under different stress state , wetting-drying tests under different stress state, wetting-drying tests with various moistened water content under certain stress state and a second time wetting-drying test when samples'deformation are stable after several wetting and drying cycles.The microscopic mechanisms of the humidification deformation and structure characteristics for coarse-grained soil are discussed by analyzing the sample's deformation property under different moistened water condition. Three existence states of water in coarse-grained soil and their individual action and affection on humidification deformation are presented. A viewpoint is expressed that humidification deformation is not certainly caused by increase of water level from the upstream and downstream, while the rainfall influent, temperature variation and condensation of water vapor could possibly cause the humidification deformation of the rockfill material in many cases.The wetting-drying test is realized first by improving the test equipment and a series tests are carried out. The test results show that it produces large deformation in coarse-grained weak rocks on first humidification but the deformation gets smaller after several wetting and drying circles. Things are different in the dehumidification process that the deformation develops continuously during the repeated wetting and drying circles besides its first clear dehumidification deformation and forms the chief part of the long-period deformation. If the stress state is changed when deformation gets stable under certain stress state, new apparent deformation in the second wetting-drying cycle occurs only when new yield deformation occurs.Unessential materials (generally weak rock) used to be put in absorption field for the rockfill dams designed in the past especially face rock-fill dams. However, it is necessary to alternate the idea considering the above tests results and the weak rocks should be applied in insensitive deformation zone and made compacted by mixing water during construction.An idea about wetting-drying test using iron wire mesh as outer boundary and combined with moistening test for coarse-grained weak rocks under different moistened water content condition has been realized in the paper. The microscopic mechanism of the humidification and dehumidification of the samples has been researched and meanwhile the practical engineering meanings are suggested which supply a reference for later research work.