The Research On Technology Of Prevention And Cure Design Of Soil Erosion Of Highway Building In Expansive Soil Regions

Soil erosion is the most serious ecological problem in the world, and it is more serious in the regions of expansive soils than other regions. The research on the soil erosion that the prevention and cure arouses in expansive soils regions is very little although the research on soil erosion is abundance in home and abroad. The serious soil erosion is brought by Nanning-Youyiguan freeway under construction in Guangxi province, and it brings out hidden troubles to the environment along the highway as the local government and people are all critical of it. In that, referring to the research of expansive soil tast of Communication Ministry West Item, this thesis studies the prevention countermeasures of the soil erosion caused by highway construction in expansive soil regions.First of all, in order to the first-hand information, the present situations of soil erosion of the region of expansive soil in Nanyou highway are investigated in details in the thesis. The results indicate the basic reasons of the soil erosion are plenty of discarding soil of cut slope and the increasing discarding soil by kinds of diseases of cut slope later not utilized by the embankment, moreover, the soil have to be borrowed to build the embankment, together with the ruleless of the places of borrowing soil and the fields of discarding soil. So the essential way of solving the problem is that take engineering measurements to utilize the discarding soil adequately under the precondition of subgrade stability, reduce the quantity of discarding and borrow soil.The major measure refer of utilizing expansive soil is soil improvement (lime improving mainly), but this method have shortcomings such as high cost, construction difficultly, and not suitable to be populary. Founded on the systematical research of the special features of expansive soil, the characteristic of the destroy of the expansive soil subgrade, and the research achievements before, the design principle of seal and cover to utilize discarding soil is established in the paper. A number of experiments and detects show that the design method of seal and cover can reduce the moisture transfer and expansive amount, weaken the action of weathering and the developing of cracks, steady the shear strength of subgrade, and the effect of preventing soil erosion is more notable.Based on the ideas of "the Design of Seal and Cover" and "Prevention Actively", four treatment methods of expansive soil embankment are applied Nanyou highway, which include Enclose side slope with non-expansive clay method, Reinforcing sideslope with geogrid method, Sandwich crushed stone solid and expansive soil and reinforcing the side slope with geogrid method, Sandwich with lime-treated soil and expansive soil and reinforcing the side slope with geogrid method, and three treatment methods of expansive soil cut slope are applied also, which include Flexible retaining wall, Sustain underdrain+Retaining wall in slope foundation, Root peg+DAH chemic solution+Retaining wall in slope foundation are utilized in the expansive subgrade of Nanyou highway, and the process of building the entity engineering are introduced in this thesis. The results of construction and experiments indicate that the expansive subgrade is stable. Moreover, the technology of preventing soil erosion of the places of borrowing soil and the fields of discarding soil which are the important source of soil erosion, but it were neglected before, then researched systematically in thesis.Finally, in order to probe the best synthesis benefit treat method of expansive subgrade, based on the technology, economy, environment protect and etc, Two methods of Set Pair Analysis and Value Engineering are applied to compare the treat methods of expansive soil subgrade for the first time in this thesis, and optimum models are made out. The analyse results of the two models show that the design schemes of Nanyou highway are feasible, practicable and have popularizing value. Furthermore, the best design projects are recommended in thesis, and this schemes may offer help and reference to the highway construction in the regions of expansive soil else.