Influence Of Grain Size Distribution On Bearing Capacity Of Moraine Soil

Moraine soils generated in Quaternary period are distributed commonly in high altitude areas,researchers home and aboard have taken a series of researches to study basic mechanical and engineering properties with indoor & outdoor experiments method successively.However,little research achievements about engineering properties of gigantic moraine soil level are found as reference,especially research of particle distribution size's effect.Firstly,latest research conclusions are reviewed,including distribution areas,shear strength,seep properties,hydraulic geologic property.etc.Then,this paper's purpose is aimed to study the the influence of particle distribution size on moraine soils bearing capacity.Huge moraine soil level of Luding station in western Sichuan is set as research goal to conduct outdoor experiments and numerical simulation method analysis.Some conclusions are made as follows :1.Grain size distribution varies badly with its location.7 group particle size analysis test in same moraine soil layer shows moraine soil's uniformity coefficient and curvature coefficient valve overlap 50 and belongs to uneven and poor grading engineering.It is a little less while moraine soil lies near to surface,and uniformity coefficient valve undulates widely far away from earth surface,while the distance is over 15 m,its value will decrease obviously.2.Shear strength has positive correlation with the content of giant group.In-situ test of huge direct shear experiment with 1m*1m size shows its that giant group content counts 60%~70%,shear strength reaches its extreme condition and internal friction angle is 37°,cohesive strength is 64.2kPa.Thus,moraine soil is a special kind of coarse-grained soil.3.Moraine soil has great creep behavior.Direct shear creep experiment shows moraine soil long term strength versus creep strength is about 0.58~0.73,4 empirical parameter calculated with 0.205,109.65,0.51 and 7.26 respectively.Experiment results are used to get creep strength parameters while internal friction angle is 36.2 °,cohesive strength is 56.2kPa,it is near to direct shear experiment result that indicts moraine soil has great creep behavior.4.Plate load test shows bearing capacity has huge difference with gravel coarse soil.Its press & deformation curve show upward concave character,and extreme valve is 3000kPa~3700kPa differs from gravel coarse soil and clay soil.5.Grain size distribution directly effect the force contact of moraine soil.Particle Flow Code(PFC2D)test shows giant group content is easily has contact stressconcentration and closed skeleton chain reflects to point-point force contact,it will block the force contact among fine particles deeply.it shows obvious stress concentration phenomenon.6.Giant group(diameter than 60mm)soil is key factor to influence press and stress character.Giant rock mass has large elastic modulus and difficultly to deform,While giant group content is over 50%,normal load has little influence to fine particles.7.Bearing capacity has correlation with its grain size distribution.While uneven coefficient is 38~45,carvature coefficient value is 1~2,which makes moraine soils get its highest bearing capacity,if not,bearing capacity decrease.At the same time,bearing capacity has positive correlation with the content of giant group(size over60mm),the more giant content is,the higher resist deformation ability shows.In contrast,boulders effect to bearing capacity are much more deeply than that of pebbles.