Experimental Research On Shear Interfacia Friction Of Fine Grained Soil

Sediment motion may cause the siltation of the watercourses and reservoirs, and not only it brings many problems to the construction of water conservancy and hydropower engineering, but also the sediment problems of the estuarine and coastal refer to the siltation of the harbor and sea-route, coastal protection, the stability of the pile foundation, the integrity of the submarine cable, the loss of landscape sand, the remediation of coastline and other issues. So the studys of the sediment motion have important implications.The problem of sediment incipient motion is a foundational topic in sediment dynamics research, and it is also the key to understanding the sediment motion. Currently the established formulas of sediment incipient motion can be attributed to three basic types, namely, the formulas of the flow rate, power, shear stress at the bottom. But many formulas derive from the incipient motion of single sediment, and derivation processes usually contain some postulated conditions in order to simplify the problem. At least two or more characteristic coefficients are included in the formulas and these coefficients are mostly reckoned by laboratory results. So these formulas have the nature of semi-theoretical and semi-empirical and they are different to be determined in the actual use. So it is necessary to design a new experimental method which does not need to determine these coefficients.In this paper, the designed measuring device of soil interfacial shear stress overcome the shortage of the direct shear apparatus of which soil is damaged along the fixed shear surface. In this apparatus, the upper shear box is not fixed, and soil is damaged along weak surface. At the same time the upper and lower shear box can install different soil which measures shear stress between the laminar soil, and it provides a research method for the incipient motion of non-homogeneous sediment layer.The shear interfacial friction of soil is mainly introduced in this paper. Compare the test data of the apparatus with the test data of the direct shear apparatus under the same condition, and analysis of the data credibility. Study the influence of clay content to interfacial shear stress using the designed measuring apparatus and analysis of the experimental results combined with the soil microstructure. The results show that the interfacial shear stress between the soil is closely related to the clay content of the soil, but the relationship is not monotonically increasing or monotonically decreasing. The interfacial shear stress gets maxima at some clay content and descends to the two sides. The interfacial shear stress and frictional force between the soil descend with the increasing of the moisture content of the soil in the upper shear box when the clay content of soil in the lower shear box is15%and the moisture content is30%. To the same soil, the faster the shear rate is, the greater the shear strength of the soil is, but the frictional force between the soil is nearly equal.According to bed shear stress formula proposed by Jonson, using the measured shear stress data, analyze the sediment incipient motion under some sea conditions. This paper s provides an experimental study method for further research on the sediment incipient motion.Although the device has been improved, there are still shortcomings. So further study on the sediment problems should be enhanced, and obtain more applicable formulas and experimental methods of sediment motion.