Research On The Disintegration Characteristics Of Compacted Granite Weathering Soils In Southeast Guangxi

Granite weathering soil is often used as cheap filler for slope and road foundation projects because of its wide distribution and easy to dig.However,the property of easy disintegration in water makes it easy to cause engineering accidents during precipitation.Therefore,it is especially important to study the disintegration characteristics of granite weathering soil.In order to analyze the difference of disintegration of soil samples with different degrees of weathering and the influence of dry density and water content on disintegration,indoor disintegration tests were conducted on different weathering zones on the same slope with granite weathered soil in southeast Guangxi area as the research object.The DCB method was used to remove free iron oxide from granite fully weathered soils,and indoor disintegration tests were conducted on soil samples with three different iron contents on different slopes,including dark,light and after iron removal,to analyze the effect of free iron oxide on the disintegration of granite fully weathered soils.The correlation between each factor and disintegration was analyzed using gray correlation analysis.The microstructure of the soil before and after iron removal was compared by SEM test.The mechanism of action of each influencing factor was discussed.The main results are as follows:(1)The disintegration test results show that the disintegration process of granite weathering soil can be divided into three stages: gentle-vigorous-smooth.The granite residual soil cannot be completely disintegrated under the conditions of higher density and water content,while the granite fully weathered soil can reach 100% disintegration rate under all compaction conditions,which has stronger disintegration than the residual soil.Under the same dry density and water content conditions,the disintegration time of granite fully weathered soil is shorter than that of granite residual soil,and the maximum disintegration rate is greater and more violent than that of granite residual soil.(2)The increase of dry density and water content will weaken the disintegration of granite weathering soil.The time required to complete disintegration of soil samples was positively correlated with dry density and water content,while the maximum disintegration rate was inversely correlated with both.(3)The magnitude of iron content is inversely correlated with the overall disintegration intensity of granitic weathered soils.The time required to complete the disintegration of granite fully weathered soil was inversely correlated with the size of iron content of soil samples;the maximum disintegration rate was positively correlated with the size of iron content of soil samples.The lower the iron content of the soil sample,the smaller the change of disintegration rate in the disintegration process.By correlation analysis,the correlation between iron content and disintegration of soil samples was slightly lower than that of dry density and water content.(4)The SEM test shows that the granite fully weathered soil before iron removal has a microscopic flocculent structure,the clay minerals are covered by the envelope structure,and the surface is rough;the minerals are mostly in edge-face contact,and the adhesion between the clay clusters depends on the bridge-like cementation structure.After iron removal,the cladding film disappears,the clay minerals are exposed,and the surface is flat and smooth;the minerals are mostly in face-to-face contact,the bridge-like structure disappears,and the clay minerals are more closely stacked in thin flakes.(5)The disintegration of soil samples with different weathering degrees differs due to the content of clay particles.The dry density of soil samples increases,the percolation path is reduced,and disintegration is more difficult.Soil samples with low water content tend to produce greater suction difference when water infiltrates,and the soil is more likely to disintegrate after force imbalance,and the disintegration effect is stronger when water infiltrates faster.The interparticle adhesion of soil samples with high iron content is more dependent on the cement structure formed by free iron oxide which is easily destroyed by water,so the stability of the soil is more easily affected when it is exposed to water.The exchange between ions in the soil also contributes to the accelerated disintegration effect.