Reinforcement Effects Of Root For Liquefiable Sandy Soil And Research On Influence Factors

Sand static liquefaction problem has always been a hot point of geotechnicalengineering research, because it is the major cause of leading landslide,mud-rock flow and other natural disasters. As a result, the researches onpreventing sand static liquefaction have vital significance. With the deepresearch on the prevention of slope liquefaction, people become more and morerealized the superiority of plant protection slope compared to other engineeringprotection methods. Vegetation protection slope technology is widely used togovern slope. It could not only reduce the cost of engineering reinforcement, butalso prevent soil erosion, protect ecological and beautify the environment, whichhas important significance to our country’s energy conservation and theharmonious development of man and nature.The paper explores the preparation methods of original root soil in thelaboratory, and three different types of mould have been designed. Theycorrespond to three different root samples: the root direction of samples inhorizontal,45°direction and vertical direction. Through cultivating vegetationdirectly in the mould, we could get minimum disturbed samples. Staticliquefaction data of original root soil could be obtained by triaxial shear test. Sixseries of triaxial shear test have been conducted, corresponding to plant density,root direction, soil initial relative density, root length and plant species. On thesame time, constant water-head saturated permeability test method is used tostudy the influence of different root distribution for soil permeability. The resultsprove that:First of all, with the plant density in a certain range, sand liquefactionpotential is decreasing when plant number increases. When the plant densityexceeds this range, the liquefaction potential settles out with the increasing ofplant number.Secondly, under lower consolidation cell pressure, root direction has littleimpact on soil liquefaction. The impact is obvious under high er consolidation cell pressure. In the meantime, liquefaction potential index of vertical rootsample is the largest and horizontal root sample is the minimum.Thirdly, when the initial relative density of soil is more than40%, theliquefaction potential index goes to zero, as a result, the liquefaction of sa nd ishard to occur. From the above results, we can get that the influence of Dr is verysignificant on sand liquefaction potential.Fourthly, under three different kinds of effective consolidation pressure, soilstatic liquefaction potential is decreasing with the root length changing from0to100mm.Fifthly, tall fescue and perennial ryegrass are two different types ofvegetation that are used to make different samples. The test results of the twokind samples are different because of the difference of root diameter anddistribution, etc.At last, the penetration test results show that the maximum value ofpermeability coefficient appears in loose sand sample group, whose plant numberis75and root vertical distribution. The minimum value appears in the samplewith70%soil relative compactness. And according to the change of permeabilitycoefficient in the table, we can get that the influence degree of initial relativecompactness is more than that of the root on soil permeability.On the basis of experimental study, three slope numerical simulations withdifferent root distribution are carried on. The results show as follows: withoutroot soil slope occurs sliding failure, and the soil slope with total root lengthdistribution has not happened. Those results show that the root length has a greatinfluence on the prevention of slope liquefaction.