Study On Expensive Soil Of Geogrid Reinforcement

Expensive soil is called disasterous soil by engineering field because of its shrink-swell, cracks and super solidated features, has caused huge loss for project development and production. Civil engineering of international and domestic has greatly appreciated the harm of the expansion. A great many methods are searched to constraint the movement of shape of the expansion, reinforcement is one of an effective way to strengthen soil. Geogrids are concerned widespread because of their big deformation modulus, good interaction with soil, construct easily and economy, now widely used in slope, retaining wall and other structures. The main test methods of geogrids reinforced are indoor triaxial test, direct shear test, pull-off test, field test and so on, has achieved great results in reinforcement effect and mechanism.Most of test and field using are horizontal reinforcement empirically at present, on basis of the research at present, vertical reinforcement is inducted in this paper, studying reinforcing effect of different reinforcement approach to expensive soil through indoor CD triaxial tests, using FLAC3D to analyze reinforcing effect of different reinforcement approach to expansive soil slope, the differences of reinforcement effect between vertical and horizontal reinforcement are studied primarily. The main conclusions are as follow:(1)During the process of triaxial shear, axial strain increases along with the increases of principle stress for all the expansive soil specimen and stabilizes finally. Stress-strain is hyperbolic form. Under different confining pressure, to achieve the same axial strain, greater the confining pressure, greater the principal stress.(2)The influence of confining pressure to drainage by consolidation is significant, higher the confining pressure is, the water displacement is bigger. Geogrids form drainage channel in the soil, can accelerate the drainage by consolidation, the best way of drainage effect is vertical reinforcement.(3) For all the reinforcement approaches, reinforcing effect from small to large is one layer level reinforcement, three layers level reinforcement and vertical reinforcement.(4)Geogrid reinforcement significantly increases the cohesion of expensive soil and has little effect on the friction angle. Improve level from small to large is one layer level reinforcement, three layers level reinforcement and vertical reinforcement.(5)In the numerical simulation, all reinforcement approach could improve the safety factor, and significantly reduced the horizontal displacement of the slope. The distribution of stress and strain of the slope is more uniform after reinforced, reducing the stress concentration of the slope. In the range of reinforcement, the stress and distribution of different reinforced ways were different. Considering all the conditions, the best reinforcement approach of this simulation is:horizontal reinforcement spacing 1.12m, longitudinal bar spacing 0.44m.(6)Considering the reinforcing effect, criss-cross reinforcement is better than single horizontal reinforcement and vertical reinforcement, because through the connection of geogrids of the criss-cross reinforced, the stability of the slope is better. But the reinforced geogrids are not the more the better, there also has the best reinforcement rate, if reinforcing more than the best reinforcement rate, reinforcement will undermine the integrity of soil and decrease the tensile strength.(7)The reinforced effect of single longitudinal reinforcement is worse than horizontal reinforcement, because if only has the vertical bas, reinforcement can hardly be fixed in the soil, and will easily slide and move with soil, otherwise in longitudinal reinforcement, scellement of grids and friction of reinforcement and soil reduce greatly, lead to the ability of limiting soil movement reduces significantly. Therefore, comparing with not reinforced slope, single longitudinal reinforcement has some effect, but is not the ideal reinforced way.