| Grab is the most widely used method for diaphragm walls (cut-off wall) construction. Grab devices include two parts: grab and grab machines. As the device directly into the land form slot, the structure performance of grab directly determines the construction cost, quality and efficiency of diaphragm wall. The direct work object of grab is soil. Study of the soil resistance to grab during the digging process is the foundation to optimize the design of grab structure. Dam cut-off wall has higher requirement on verticality, systematic study on the guide methods and effect of grab provides the basis for selection and design of guide system.In this paper, the research of grab consists of three aspects: resistance, guide methods and design. Details as follows:(1) Based on the existing calculation model of grab grasp resistance, the author utilized plastic limit theory created the analysis model of grab push resistance, and deduced the formula for calculating the push resistance. The formula was proved by cited test data. And then, the author analyzed the influence of the cut depth, cut angle, soil cohesion, internal friction angle and density on pushing resistance by the formula.(2) Using finite element analysis software ANSYS / LS-DYNA simulated the force in the contact process of teeth with soil. The contact force is the cut resistance. The author analyzed the relationship of cut angle, cut depth and teeth contact force. The conclusion of analysis soft is similar to the results of experiment. So, it is feasible to research cut resistance by experiment.(3)The author analyse the reasons of deviation in the process of digging and carry a systematic research on the guide methods.(4)The author introduce the design-ideas of DSG-800 hydrulic grab and expound the design-process form three aspects, including mechanism,fluid drive and electric controls.(5)The author concludes the zero-point of deviation measurement and estimate the function of the grab by the example project.
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