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为了观测土工格栅加筋影响带的范围,采用特制的一侧透明的拉拔盒,共对6种不同级配的粗粒土分别完成了4种法向压力下的拉拔试验。通过预埋于土中用大头针尖制作并包裹于导线皮中的位移观测点,直接观测了土工格栅在粗粒土中拉拔引起的土粒位移,发现格栅的拉拔会带动其上一定厚度范围内的土体发生移动,这个范围称之为加筋影响带。试验发现平均粒径d_(50)>0.83 mm的粗粒土中,土工格栅加筋影响带的厚度δ与试样的法向压力没有关联,主要与土粒级配有关,当d_(50)<1.05 mm时,δ随d_(50)的增大有较显著的增加;而当d_(50)>1.05 mm后,这种趋势明显减缓;特别是当d_(50)>1.65 mm后,二者呈良好的线性递增关系。基于这一试验结果,提出了考虑加筋影响带的加筋土坡稳定性分析方法,简称影响带法。在这一方法中,认为土工格栅的加筋作用相当于增加了加筋影响带内土的黏聚力,而内摩擦角不变。从而将加筋土坡简化为成层土坡,使计算大为简化。而计算得到的加筋土坡稳定安全系数在加筋层距不大于0.6 m,且格栅抗拉强度大于20 k N/m时,与有限元强度折减法的计算结果符合良好。
In order to observe the scope of the influence zone of geogrid reinforcement, a special drawing box with a transparent side was used. Four kinds of coarse grained soil with different grading were completed four kinds of drawing tests under normal pressure respectively. The displacement of soil particles caused by the drawing of the geogrid in the coarse grained soil is directly observed by the displacement observation point embedded in the soil and made by the pin tip and wrapped in the conductive wire skin. Soil within a certain thickness range of movement, this range is called reinforcement belt. It is found that the thicknessδ of the influence zone of the geogrid reinforcement is not related to the normal pressure of the sample in the coarse grained soil with the average particle size d 50 (50)> 0.83 mm, which is mainly related to the grading of soil particles. When d 50 ) <1.05 mm, δ significantly increases with the increase of d_ (50), while when d_ (50)> 1.05 mm, the trend slows down significantly. Especially when d_ (50)> 1.65 mm, The two showed a good linear relationship. Based on the results of this experiment, a method of stability analysis of reinforced soil slopes considering reinforcement zone is proposed. In this method, the geogrid reinforcement is considered to be equivalent to increasing the cohesion of soil in the belt with reinforcement, while the internal friction angle remains unchanged. So the reinforced soil slope is simplified as stratified soil slope, so the calculation is greatly simplified. However, the calculated safety factor of reinforced slope is in good agreement with the strength reduction method of finite element method when the distance between stiffened layers is not more than 0.6 m and the tensile strength of grid is more than 20 kN / m.