Test Study On The Mechanical Properties Of Lime-Treated Soils In Expansive Soils Roadbed

Study on the mechanical properties of lime-treated soils in expansive soils roadbed is carried on both laboratory and field tests. All kinds of impact factors on performance of lime-treated expansive soils are studied. It will provide scientific basis for study on long-term performance of lime-treated expansive soils roadbed.The main scope and achievements of this thesis include follows.(1) It shows that Naling expansive soils belong to weak and intermediate degree of swelling clay with Middling to high compressibility, compacted expansive clays has features of higher swell potential, bad water stability and lower intensity as base on study on general physical, mechanical and physicochemical characteristic of original and compacted expansive clays. It is put forward that Naling expansive soils cannot be directly used as fill. The distribution of the complete pore and the swelling-shrinkage mechanism are drawn out.(2) It shows that soil types, swell potential and standard absorption features are changed after expansive soils are treated by lime as base on testing study on moisture content of standard absorption for lime-treated expansive soils. It is proved that the index of moisture content of standard absorption lime-treated expansive soils is invalid to represent swell potential of lime-treated expansive soils.(3) The best lime content, the maximal dry density, the best moisture content, the shear strength and change rule with curing time of lime-treated expansive soils intensity are obtained from testing study on expansive soils treated by lime. It is verified that the strength of lime-treated expansive soils increase with curing time, and remain steady in 60 day.(4) The variation laws of the dynamic elastic modulus and damping of expansive soils and lime-treated expansive soils with dynamic strain, vibration frequency, confining pressure, consolidation ratio, lime content and so on are obtained from dynamic triaxial test. Dynamic strength of 6% lime-treated expansive soils roadbed can meet a demand for the long-term traffic load.(5) Based on test study on the strength of lime-treated expansive soils with climate change, the strength degradation rule of lime-treated expansive soils are put forward under cyclic wetting and drying, freezing and thawing, and leaching. It is remarkable that the strength of lime-treated expansive soils vary with climate change. For the long-term stability of lime-treated expansive soils roadbed,the measures must be adopted to reduce the impact on the strength of roadbed with climate change in design and construction.(6) Based on field tests study on roadbed of lime-treated expansive soils, controls parameters of rolling compa-ction are obtained, it is drawn out that bearing behavior, water stability, and strength characteristics of lime-treated expansive soils roadbed, as the main protective measures of lime-treated expansive soils roadbed are put forward. it is described that surface cracks of road-bed spread with climate change, the cover measure can be useful to avoid surface cracks of roadbed,(7) For the long-term stability of lime-treated expansive soils roadbed, Border soil and composite two geotextile one geomembrane are adopted, and its design and construction are discussed.