Stability Analysis Of Expansive Soil Channel Slope Under Drying-Weting Cycle

Expansive soil is a special soil that is sensitive to the humidity state.It is often in the unsaturated state in the natural state,which has a controlling impact on the stability of the channel slope.The long distance water conveyance channel in northern Xinjiang is a linear project,which passes through the expansive soil area along the line.Therefore,it is of great significance to study the stability of the expansive soil channel slope to ensure the production and living water of the masses.This thesis takes an expansive soil water conveyance channel in northern Xinjiang as the research object,and analyzes the change rules of deformation,strength and permeability characteristics of expansive soil in the channel foundation under the dry-wet cycle through laboratory tests;Using image processing technology,the fracture parameters of the sample surface fracture image are extracted,and the fracture evolution law of expansive soil under dry-wet cycle is analyzed;Based on the grey correlation theory,the relationship between the surface crack parameters of expansive soil and the deformation and strength characteristics of soil is explored;Based on the field data and test data,a two-dimensional plane model is established to calculate the safety coefficient of the expansive soil water conveyance channel slope,and analyze the stability state of the channel slope under the action of different dry-wet cycles and sudden water level drop.Finally,based on the elastic foundation beam theory,the mechanical model of the deformation and internal force of the concrete lining plate of the channel is established,and the variation law of the deformation and internal force of the concrete lining plate of the expansive soil water conveyance channel under the dry wet cycle is quantitatively analyzed,which provides a theoretical basis for the damage evaluation of the concrete lining plate of the expansive soil water conveyance channel.Based on the above research,the preliminary conclusions are as follows:(1)As the number of wet and dry cycles increases,the expansion rate and expansion force of expansive soil decrease with and without load.Among them,the reduction of unloaded expansion rate is greater than that of loaded expansion rate.The reduction is significant after the 1st to 3rd cycles,and the reduction is slow after the 4th to 5th cycles,ultimately tending to stabilize;The peak strength of expansive soil decreases significantly,and the stress-strain curve gradually transforms from a softening curve to a hardening curve.The shear strength value gradually decreases,the cohesion decreases significantly,and the change in internal friction angle is relatively small;The saturated permeability coefficient of expansive soil has increased.(2)As the number of dry wet cycles increases,the change stages of surface crack rate in expansive soil can be divided into rapid growth period,slow growth period,and stable growth period.The relative area of surface cracks in expansive soil shows a pattern of first increasing and then decreasing;As the compaction degree of expansive soil increases,the surface crack rate and relative crack area of expansive soil decrease;The number of surface cracks in expansive soil shows a high correlation with unloaded expansion rate and expansion force,and the number of cracks and crack rate are closely related to cohesion.(3)As the operating years of the channel increase,the displacement of the channel slope gradually increases,and its safety factor gradually decreases.The instability mode of the channel slope changes from deep landslides to shallow landslides;Extending the drainage time of the channel can effectively increase the safety factor of the channel slope,thereby improving the durability of the channel;It is recommended that the drainage time of the channel should not be less than 4 days,and the inspection and maintenance period should not be longer than 5 years.(4)As the operation period of the channel increases,the displacement,expansion reaction force,bending moment,and shear force of the channel lining plate show a pattern of first increasing and then decreasing.After 2 years of operation,the lining plate is prone to damage,with the maximum displacement of the lining plate occurring in the middle of the channel bottom and the lower part of the channel slope.The maximum expansion reaction force and shear force occur at the foot of the slope at both ends of the channel,and the maximum bending moment occurring in the middle of the channel bottom and about 1m away from the slope foot.