The Research On Simulating Of Soft Rock Layer To Aim At A Large Diameter Drilling With Similar Materials

With rapid development of the socialist modernization, the large-diameter drilling has been applicated in soft rock layer more and more,but often in the poor drilling efficiency in high intensity and brittleness of soft rock layer. Therefore, it is urgent to do some simulation test of drilling in soft rock layer to study and optimiz the suitable drilling equipment and drilling parameters, to enhance drilling efficiency and reduce the construction cost. But sample the natural soft rock is too difficult, and the drilling simulation experiment results in soft rock will be great impacted by the inhomogeneity and anisotropy of natural rock.The thesis analyzes the crushing mechanism of the soft rock layer, using the Qingdao bay bridge pile foundation engineering geological data and the physical and mechanical properties of soft rock as the prototype, and adopts the similar materials such as cement, gypsum, sand and clay etc. to simulate the mudstone formation(include shale and silt mudstone), siltstone(include spelitic siltstone) and fine sandstone(include slity fine sandstone) the three typical models of soft rock by using similar principle and Orthogonal Design. The thesis also uses of Excel software to analyze the test results, summarizes the relationship of the indoor small models and outdoor large models, and analyzes all kinds of main materials and the influential factors of the maintenance conditions on the module performance. This test has overcome the above difficult problems of sampling the natural soft rock, provided better foundation for the research on the large-diameter drilling parameters in soft rock layer and filled the gaps of the research on materials simulation aiming at large-diameter drilling parameters in soft rock layer.The thesis also studies the character of soft rock with water such as swelling, disintegration and easy to carry out, and analyzes the soften of single axle compression strength and the recovery of shear strength with water. Ultimately this study has determined the issue of the simulating of soft rock layer accord with the actual project and also filled the gaps of the research on simulating of soft rock aiming at it's character at home.