Experimental Study On Laboratory Surface Vibrating Compaction Parameters And Soil Structure Type Analysis Of Coarse-Grained Soils

Surface vibrating compaction is an important method to test the maximum dry density of coarse grained soil which has been chosen in test code for road and railway. The surface vibration compaction comes from the idea — "it’s closer to the actual situation of vibratory roller ", as for laboratory test,which mainly study on the parameters influencing the test result. Having surface vibration compaction on coarse grained soil to measure the bration parameters and discussed the control of parameters of surface vibratory compaction, compared with the heavy compaction test combined with test results and compaction effectiveness; based on void-filling principle of coarse-grained materials, have a study on the soil body structure of two typical natural coarse grained soil filler at alpine region.Main contents and conclusions:(1)Having test surface vibration compaction on gravel filler of test section of high-speed railway sub-grade, installed vibration sensors at the same time.discussed the problems about the control of parameters of surface vibratory compaction based on the industry norms and the study results. the maximum dry density values is influenced by the exciting force, vibration frequency, amplitude, the time of vibration and so on. exciting force belongs to the inherent properties of compaction machinery. Action force relates to the nstrument parameters and soil characteristics, measured action force is greater than the instrument force, the specification for road, railway regulates that setting value range 10-80 of "exciting force" as the peak action force when steel tamping contact with the soil surface is more reasonable. Vibration compaction significant effect time is about lmin and reasonable time is 3min. For same kind of gravel soils sample, the maximum dry density of surface vibration compaction test is smaller than the Z3 heavy compaction test,the former accounted for 96% of the latter. Compared with the vibration compaction, the compaction impact load will be easier to make coarse grained soils dense.There are two kinds of reference ideas for choosing suitable parameters of lab vibrating compaction test. Firstly, setting fixed parameters,to develop a unified parameter standard. Secondly, optimizing reasonable range,setting parameters that can be adjusted, according to different types of coarse grain soils, select the appropriate parameters.(2) Making the two types of natural coarse grained soils filler in the alpine area as test samples. Based on the void-filling principle, after removing the minimum particle size group of soil samples, the surface vibration compaction test was carried out to test the dry density. According to the change of the law of dry density,analysis the soil structure types and identify demarcation particle size between skeleton granule and filler particles. All the research findings provide reference for the improvement of coarse aggregate gradation.With the removal of the upper primary particle size group, The variation regularity of dry density show that the dry density of dense suspension structure coarse grained soil increase first and then decrease and change is significant, The demarcation particle size is obvious, and the two-component structural characteristics are significant.For the coarse grained soils of pore skeleton structure, the dry density increase or decrease,there is no big change, and the demarcation particle size is not obvious. For the coarse grained soils of dense skeleton structure, dry density curve is relatively smooth. The increase of pore volume is relatively small, after removing the minimum particle size, the remaining particle size particles also show a good filling relationship with each other, the soil structure assumes multiple.Coarse grain content controled in 30%～70% is a necessary condition for the formation of soil skeleton structure, fine grain (d<0.075mm) content of the boundary value li mitedat 5%～10% is relatively reasonable. For coarse grained soil, the boundary diameter ca n be used as the boundary,analyze the composition of soil aggregate gradation and the type of soil structure by stages. When the uneven coefficient of coarse grain is very large, the curv ature coefficient is not the strict control condition of the grade.