Study On The Influence Factors Of Unsaturated Purple Soil Shear Strength

The shear strength of soil is an important reference index in engineering design, but also the soil precision farming, a basic design parameters of large agricultural appliances. Along with the agricultural foundation engineering construction in southwest hilly area increasing, research for the mechanical properties of purple soil engineering has brought new opportunities. Purple soil as a soil type is widely distributed in Southwest China, its mechanical properties will show obvious difference with other types of soil, not simply with the study of other types of soil results to set for the study of soil mechanics properties of purple. As the land consolidation project demonstration area, countries will have a larger scale agriculture engineering construction investment of every year in Chongqing city. In the land consolidation project, irrigation and water conservancy engineering and design in the field of road engineering and construction process must involve to the study and calculation on soil mechanics properties of the construction area, so it is very necessary to study on soil areas of purple soil shear strength, the agricultural industry in the area of engineering design and construction has important know significance. Although the soil anti shear strength is affected by many factors, but the moisture content and particle composition is the main factor affecting the strength properties of purple soil. This thesis chooses Suining group, Feixianguan group and Shaxi Temple group three red brown purple soil, different geological formation of dark purple and grey brown purple soil as the research object, the moisture content and particle size as a variable, studied the shear strength characteristics of these three kinds of soil using TSZ automatic three axis instrument, and combining with the test results, the suggestions on agricultural engineering design and construction within the region is proposed. The main results are as follows:1water content of unsaturated soil shear strength effectEffect of water content on three kinds of purple soil development in different geological time in case of different. The cohesion (c) showed significant difference with the change of water content, with the increase of moisture content in the red brown purple soil and grey brown purple soil cohesion (c) showed a decreasing trend after the first increase, the maximum cohesive force red brown purple mud (c) appeared in the water content was11%, Ash Brown Purple mud of the most high cohesion (c) occurs when the moisture content is13%, and the cohesion of dark purple mud with water content of two peak change process, moisture content of11%and17%respectively; three kinds of purple soil development in different geologic time internal friction angle ((p) change with law of water content is the same, are showing increased gradually becomes smaller with increasing water content.Three kinds of different developmental ages of purple soil in aqueous default rate the same dry density and the state of its shear strength value differences, three kinds of purple soil internal friction angle and cohesion values, show more obvious differences, specific performance for the cohesion of grey brown purple soil was higher than that of red brown purple and dark Purple mud, so its anti shearing ability, road use is more good, in the engineering construction, type exchange filling should be preferred mechanical properties of gray brown purple soil, and in the dark purple soil distribution area due to the bearing capacity of the foundation soil is not stable enough, to deal with material in engineering construction strict screening, the higher the bearing capacity of the foundation stone and other materials should not be used as a construction material.2particle size gradation on strength of non shear saturated purple soilParticle size gradation of three different developmental ages of purple soil shear strength have different effects, mainly influence the particle size gradation of three kinds of purple soil shear strength for its internal friction angle (φ) influence, the cohesion (c) has less effect. The red brown purple soil and grey brown purple soil shear strength is influenced by the particle size gradation were graded soil sample grain size of soil with higher content of the cohesion and internal friction angle increases, the shear capacity is higher; and the particle size gradation of purple dark influence the shear strength of the clay is different from the first two, D graded soil sample shear soil the highest strength evenly mixed into three size of soil grey brown purple soil, the mechanical properties of fine grain content of more than a grade distribution samples, the rest three graded soil shear strength along with the fine grain size of soil content is proportional to the size ofComparison of three different development geological age of purple soil in different particle size gradation of shear strength parameter values can be found, dark purple clay inner friction angle (cp) is higher than the same grade red brown purple soil and grey brown purple soil, the grey brown purple soil cohesion (c) is higher than that of the red brown purple mud and dark purple mud. The purple soil mechanical properties after the remodeling due to particle composition change by a certain degree of change, and grey brown purple soil affected and changed the minimum level, so that the mechanical properties of the most stableAccording to the above conclusion to the engineering design and construction puts forward the recommendations are as follows:The engineering layout in different purple soil area should use the default program different in order to ensure the engineering stability, and section design in road design, the hydraulic erosion serious regional using stone and gravel subgrade bearing capacity strengthening, in different soil types area should be planning and design different, dark purple soil distribution area if the construction, you should not use stone such as high bearing capacity of foundation materials as raw materials; and as far as possible the use of mixed a variety of different thickness of the material in the reinforcement treatment on road engineering road base is strengthened when spread foundation bearing capacity.To sum up, many factors that affect the shear strength of soil, and the same factors on different soil shear strength have different effects, this paper only selects the moisture content more extensive research and particle size distribution of two kinds of factors are studied, the effect of different types of purple soil shear strength the situation. The effect of soil shear strength of many factors, such as plant roots, with effect of compaction as well as the size of the long-term effect of artificial disturbance on soil properties. And the Chongqing area of purple soil has many kinds, the research further, in order to further improve the basic theory research of mechanical property of soil in Chongqing area.