Study On The Characteristics Of Reinforced Expansive Soil And The Dry-wet Circulation Test Of The Slope

The rainfall and evaporation repeatedly makes the swelling-shrinking deformation of theexpansive soil slope.This drying-wetting cycles result the phenomenon of crack evolution,which may lead to the landslide and collapse, etc. Geogrid reinforcement technology on theone hand to solve the probelm of serious fissures zone, on the other hand limits the expansiondeformation of the expansive soil. The thesis focuses on the use of the basalt fibers geogrid inthe expansive soil slope and a series of studies was carried out to investigate of thedrying-wetting cycles characteristics of expansive soil slope.This thesis introduces the reinforcement theory and the application research of the opticalfiber sensing technology, and the research status of triaxial test and the drying-wetting cyclestest were introduced then. It was proved that the self perception geogrid which the intelligentFBG sensor compounds in basalt fiber geogrid be used for the monitoring early warningsystem. This intellisense materials will protect the slope, and at the same time achieve thelong-term health monitoring.The conventional triaxial test was carried out to explore the strength and deformationcharacteristics of expansive soil samples with the new reinforced materials—basalt fibergeogrid.The results show that saturated soils performanced for the plastic damage andunsaturated soil samples produced partial brittle failure. With same type of reinforcement,unsaturated soil was far greater than the cohesion of saturated soil, whereas the internalfriction angle changes slightly. Compared with the unreinforced soil, the initial yield stress andthe peak strength of reinforced soil increased. The internal friction angle and the cohesionincreases gradually with the increasing layers of geogrid.The model test of drying-wetting cycles was carried out to explore drying-wetting cyclescharacteristics and reinforcement characteristic by monitoring water content, soil pressure,expansion and contraction deformation, strain characteristics and crack development duringthe cycles. The test results show that, the drying-wetting cycles intensified the crackdevelopment, destroying the structure integrity and stability of the slope. Drying-wettingcycles function mainly influenced on shallow soil, and the expansion potential of the slopegradually decreased with the increasing cycles. Basalt fiber grille reinforcement significantlyinhibited the soil deformation, and made a certain degree of containment of the slip surface in soil slope,enhancing the stability of the slope.With the increasing drying-wetting cycles, crackdegrees (crack area ratio and the crack length ratio) increased, and reinforcement significantlycurbed the fracture development. At the same time, the reinforced effect became better withthe increasing cycles.The strain shows the internal soil structure and its consistency with thedisplacement make the expansive soil slope realizing the perception monitoring.