| Check dam is an effective form of integrated river basin management which should be implemented according to specific local conditions. It generally contributes to the extension of arable land, the improvement of agricultural productivity, as well as the soil erosion prevention.But in Northern Shaanxi Jingbian, Dingbian area, a considerable part of warping dam due to the special geographical location, coupled with the majority of warping dam is not set filter equipment, resulting in warping dams produce seepage failure caused by dams, the problem early in the 1980 s have been found, but has not been resolved. To local warping dam posed a serious security risk, how to control the warping dam after seepage failure has become an important problem of Warping Dam Construction in the local control. Taking Jingbian County of Yulin City, Shaanxi Province sand whorl ditch of Warping Dam silt loam and sandy soil of two kinds of dam soil as the research object, through the penetration of raw soil material destruction test, filter the filter test and a series of tests as the use of new materials after the destruction of penetration test, new solid material. Using the Malvin laser particle size analyzer, scanning electron microscope and mercury analyzer before and after the inquiry from the micro perspective and contrast soil filter layers structure changes, explore the high strength, good effect of anti seepage curing material filter, and quantify the reasonable gradation for the North Shaanxi Jing region produced by dam seepage failure reinforcement to provide theoretical basis and technical support, has important practical significance of the study.(1) seepage dam soil damage test conclusion1) As indicated by the results of tests, seepage damage process with two different kinds of earth material included four stages. For the observation of silty loam, firstly the boiling bubbles appeared, then surface soil mildly upheaved, after fissures fully developed, the critical surface finally muddied. For aeolian sandy soil, on the other hand, the third stage would be a specific phenomenon named sand boiling, while others were totally alike.2) With the improvement of water head, the seepage flow with two different kinds of earth material both showed an approximate linear growth before the seepage failure; but after the first specific soil particle moved, with the increasing of the head, seepage flow increased rapidly. The seepage failure happened in silty loam soil lasted far longer than the aeolian sandy soil; the seepage damage critical gradient also showed a same tendency.3) For all the soil samples with different types of earth material, SEM observation and mercury porosimeter test has been carried out and concluded thatafter the seepage failure, characteristic parameters of both soil pore(i.e. the porosity, the mean diameter) and soil particles(i.e. the mean diameter of soil particles) varied with the height of soil column(the top layer < the middle layer < the bottom layer), and their geometric parameters illustrated no definite changing regularity.(2)The conclusion of seepage failure test with different stabilized soil.According to the seepage damage tests on both two kinds of soil sample mixed with different kinds of stabilizers, there are several conclusions:1) The lime stabilizer(116.28%) tend to improve the critical gradient of medium silty loam most, followed by the cement curing agent(68.53%) and the polypropylene fiber stabilizer(42.13%); for the aeolian sandy soil, by contrast, the polypropylene fiber curing agent(293.59%) turned out to be the highest improver, while the cement(93.93%) and lime(68.63%) ones provided a much lower potential.2) When it comes to the ability of optimizing the seepage flow, the polypropylene fiber stabilizer(308.60%) performed far more better than the cement curing agent(211.83%) as well as the lime ones(-24.73%) for the medium silty loam, and showed a similar trend for aeolian sandy soil(36.76%), followed by the cement curing agent(-26.47%) and the lime stabilizer(-47.06%).In conclusion, mixt soil stabilizer(with lime and polypropylene fiber) should be the best fit of anti-filter material.(3)The conclusion of anti-filter material test.The optimum proportion(mass percent) of anti-filter material is: 98.04% dry soil + 0.73% cement + 1.22% polypropylene fiber. As can be seen from the SEM analysis, the pore ratio of best fitted anti-filter material is 13.67%, and the average pore diameter is 0.755μm. |
