Soil Mechanics Characteristics Of Red Clay In Middle Region Of Guangxi

Based on the red clay of in Middle Region of Guangxi province(including Liuzhou city, the road of Tiebei and Lailiang in Laibin city) as a main research object, combined with the existing test data of red clay in Guilin and Wuming, systematically analyzing the mechanical properties of red clay in middle of Guangxi region, and by means of the X-ray diffraction experiment, scanning electron microscopy (SEM) and Energy Dispersive Spectrometer,mercury injection test and nitrogen adsorption test to explain macro mechanical characteristics and the cause of red clay in some micro aspects,such as mineral composition, microstructure and pore distribution. The main results were as follows:(1) From the surface to the bedrock of the red clay section in middle Region of Guangxi, void ratio and the moisture content increased gradually, density, dry density decreased gradually; Liquid limit, plasticity index, the free expansion rate and contractility increased gradually, and the stratification has been displayed; The content of illite, Vermiculites and clay show positive correlations to the red clay’s liquid limit, plastic limit, plasticity index and swell-shrink(2) In Liuzhou and Laibin city of Guangxi province, the mainly component of red clay minerals are quartz, kaolinite, illite and goethite. The main component of mother rocks is calcite. One guest iron north road contains a small amount of vermiculite and organic matter, organic matter holds water and reducing impact mechanical properties of red clay;The cation exchange capacity from the surface to the bedrock increases gradually, the space of cation exchange activity became smaller, the agglomeration of granule gradually increased and stabilized.(3) Red clay area in Middle Region of Guangxi special "aggregate" structure model, with the growing of laterization, free iron oxide red clay in the aging effect between aggregate porosity change, so as to make the red clay section presents different structural. The aging effect of free iron oxide in red clay make the soil to has its own structural features, namely it shows the developing trend from the structure of turbulent and enclosed flocculation structure to lamellar stacking structure, thus to influence the strength of the soil.(4) Red clay with high void ratio in Middle Region of Guangxi in compressibility and strong shear strength. Red clay section from the surface to the bedrock, over-consolidation property, cohesion and internal friction Angle became smaller, and showed obvious stratification phenomenon; This is the opposite of the change trend of normally consolidated soils, red clay on "under the hard soft" characteristics. Mechanical properties and red clay section gather pore body assumes the inverse correlation between the content and goethite content was positively correlation; Namely along with the increasing of goethite, effective strengthen cementation of red clay, which gathered the body pore reduced, consolidation performance surplus characteristic gradually enhanced; Verify the change regularity of red clay section laterization degree;(5) The CIA index is suitable for the degree of weathering of red clay in Middle Region of Guangxi. Deduce the formation of red clay in Guangxi need three steps:the first step, the mother rock dissolution, leaching, metasomatism and other physical and chemical weathering. The second step, entered the laterization process. The third stage, entered the red clay consolidation process.(6) Disturbance and compaction of CBR peak goethite, clay content was positively correlation, bubble water4days strike the optimal moisture content significantly larger sample; Compaction sample after bubble water4days to process, soil water absorption expansion so that the specimen strength sharply reduce, expand the greater the amount of the CBR lower amplitude. Adopt the most unfavorable condition (bubble water4days), control of dry density as filled soil quality index is more suitable for engineering practice.