Research On The Unconfined Compressive Strength Properties Of Yunnan Laterite Under The Action Of Drying And Wetting Cycles

The topic of this paper comes from the National Natural Science Foundation Project "Research on the effect of dry and wet cycles on Yunnna laterite dam"(Project No.51568031).Many problems still exist in the study of the unconfined compressive characteristics of Yunnan laterite.This paper aims at providing some reference for the solving of the problems of dam and reservoir bank slope crack in dry season and deform in rainy season under distinct climate of Yunnan Province.Yunnan laterite is taken as the research object,with the order of dry and wet cycle as the control conditions,humidification followed by dehumidification is the wet-dry cycle,and dehumidification followed by humidification is the dry-wet cycle,and the influences of cycle times,cycle amplitude,cycle temperature,initial moisture contene and initial dry density are also considered,the unconfined compressive strength characteristics of Yunnan laterite under dry and wet cycles were studied through indoor uniaxial unconfined compressive strength tests.It is of great significance for practical engineering.The results show that the failure characteristics of laterite under unconfined wet and dry cycles are as follows:(1)Under the action of wet-dry cycle,the dehumidified laterite with different wet-dry cycle times,different wet-dry cycle amplitude,different initial moisture content and different initial dry density collapses directly after failure;the dehumidified laterite with different wet-dry cycle temperature produces through cracks after failure,accompanied by soil falling off.(2)Under the action of dry-wet cycle,the failure of humidified laterite with different dry-wet cycle times,different dry-wet cycle amplitude,different dry-wet cycle temperature,different initial moisture content and different initial dry density results in through cracks and soil falling off.And with the increase of each influencing factor,the larger the cracks after failure,the greater the degree of soil shedding.(3)Comparison of the failure characteristics of wet-dry cycle and dry-wet cycle: under the influence of different cycle times,different initial moisture content and different initial dry density,the damage degree of dehumidified laterite is higher than that of humidified laterite;under the influence of different cycle amplitude,when the cycle amplitude is high,the damage degree of dehumidified laterite is higher than that of humidified laterite;when the cycle amplitude is low,the damage degree of dehumidified laterite is similar to that of humidified laterite Under the influence of different cycle temperature,the damage degree of dehumidified laterite is similar to that of humidified laterite.The unconfined compressive strength characteristics of dewatered laterite under wet-dry cycle show that:(1)under various factors,the stress-strain relationship of plain laterite before wet-dry cycle presents a strain softening curve with lower softening degree;after wet-dry cycle,the stress-strain relationship of dewatered laterite presents a strain softening curve with higher softening degree.(2)Compared with before wet-dry cycle,the unconfined compressive strength of dewatered laterite increases and the peak strain decreases after wet-dry cycle.(3)With the increase of wet-dry cycles,the unconfined compressive strength of dewatered laterite decreases gradually,and the peak strain decreases gradually;when wet-dry cycles are 1-2 times,the unconfined compressive strength of dewatered laterite increases the most,and then decreases gradually.(4)With the increase of wet-dry cycle,the unconfined compressive strength and peak strain of dewatered laterite first increase and then decrease,and the peak value is 12.0%.(5)With the increase of wet-dry cycle temperature,the unconfined compressive strength and the corresponding peak strain decrease.(6)Before the wet-dry cycle,the unconfined compressive strength decreases and the peak strain increases with the increase of the initial moisture content;after the wet-dry cycle,the unconfined compressive strength increases and the peak strain increases with the increase of the initial moisture content.(7)With the increase of initial dry density,the unconfined compressive strength and the corresponding peak strain increase.The unconfined compressive strength of the wet red soil under the dry-wet cycle shows that:(1)under various factors,the stress-strain relationship of the pure laterite is a strain softening curve with low softening degree before the dry-wet cycle;after the dry-wet cycle,the stress-strain relationship of the wet red soil also shows the strain softening curve with lower softening degree.(2)Compared with the dry-wet cycle,the unconfined compressive strength and peak strain of the wet red soil decreased after the dry-wet cycle.(3)With the increase of dry-wet cycle times,the unconfined compressive strength of the wet red soil decreases gradually,and the peak strain decreases gradually;when the dry-wet cycle is 1-2 times,the unconfined compressive strength of the wet red soil decreases the largest,and then decreases gradually.(4)With the increase of the range of dry-wet cycle,the unconfined compressive strength of the wet red soil decreases,and the corresponding peak strain decreases.(5)With the increase of dry-wet cycle temperature,the unconfined compressive strength and the corresponding peak strain of the wet red soil decrease.(6)Before the dry-wet cycle,with the increase of initial water content,the unconfined compressive strength of the plain red soil increases,and the corresponding peak strain increases;after the dry-wet cycle,with the increase of the initial moisture content,the unconfined compressive strength of the wet red soil increases,which is equivalent to the peak strain.(7)With the increase of initial dry density,the unconfined compressive strength of the wet red soil increases,and the corresponding peak strain increases.(8)The influence of the sequence of dry and wet cycles: under various factors,the unconfined compressive strength of dehumidified laterite is much greater than that of the wet soil.That is,in dry season,the unconfined compressive strength of laterite is the largest,but when the rainy season comes,the unconfined compressive strength of laterite will decrease sharply.