不同频度和强度的干湿循环对花岗岩红壤固结强度的影响OA北大核心CSTPCD

[Background]Erosion-induced collapse is the most intense and severe type of erosion in the southern tropical and subtropical regions of China.The combination of abundant water and high temperatures in this region leads to variations in soil moisture due to temperature and changes in rainfall intensity and frequency.These changes result in frequent cycles of wet and dry conditions,and increase the probability of collapse.As Gan county being an area with the highest,most concentrated,and clustered erosion intensity,this study was carried out in Gan county,Jiangxi province,with the aim of providing a theoretical basis for predicting the degree of occurrence and development trend of collapse erosion.[Methods]We collected the samples from the surface granitic red soil in the Jingouxing sub-watershed characterized by a subtropical hilly-mountainous climate with concentrated rainfall from April to June,which was subjected to wetting-drying cyclic tests with different frequencies and intensities,followed by rapid consolidation tests.By analyzing the e-p curves and the amount of consolidation sedimentation,we summarized the changes in consolidation intensity of granite red soil during humidification and desiccation,as well as the change rule of consolidation intensity under different frequencies and intensities of wetting-drying cycles.[Results]1)The porosity ratio demonstrated a trend of first rapid reduction with increasing loading pressure,followed by a tendency of stabilizing.Wetting-drying cycles intensified the compression deformation of granite red.During the first 7 cycles,the porosity ratio followed the pattern of medium intensity＞low intensity＞high intensity.After 7 cycles,porosity showed no clear intensity-related pattern,indicating stabilization in both soil compression and deformation.2)With the increase in frequency and intensity of wetting-drying cycles,both instantaneous soil sedimentation and main consolidation sedimentation had a gradual increase.At the 10th cycle,there was a rebound in the increment of instantaneous sedimentation,reducing by 0.079 mm compared to the 7th wetting-drying cycle.The impact of wetting-drying alternations on the soil's instantaneous sedimentation diminished after 7 cycles.3)The compression factor of the granite red soil after wetting-drying cycles ranged from 0.8 to 1.0,indicating high soil compressibility,and it increased slowly and stabilized after seven cycles.The factor of consolidation showed a continuous decreasing trend with the increase of the frequency and the decrease of the intensity of wetting-drying cycles,the soil structure was damaged,the intensity of the soil was reduced,and the degree of destruction of the soil tended to be complete after seven cycles.4)The frequency of wetting-drying cycles had the most significant effect on the changes in consolidation and compression factors(F=4 102.71,P＜0.001,F=508.40,P＜0.001),but the effect of the interaction between frequency and intensity was weak(F=6.57,P＜0.05;F=2.32,P＞0.1).[Conclusions]After seven cycles of wetting and drying,the alternating wet and dry conditions result in a weakening impact on soil sedimentation and consolidation properties,sedimentation and consolidation properties of the soil diminish.There is a relatively weak interaction between the frequency and intensity of wetting-drying cycles.The results of the study indicate that seasonal precipitation and drought-induced wetting-drying cycles primarily affect soil consolidation intensity,enhance soil homogeneity,and exacerbate the risk of instability and collapse.