Comparative Studies On The Infiltration Characteristics And The Influential Factors Of Undisturbed Soil And Disturbed Soil For A Loess Landslide

The landslids body is a typical disturbed soil formed by the loess slope body sliding toward the free face.Compared with the undisturbed loess,the physical properties and mechanical properties of the disturbed soil have changed greatly,which leads to significant differences between disturbed soil and undisturbed soil in the infiltration characteristics.The differences are the important reference and evaluation indicators in soil erosion assessment of typical watersheds,numerical simulation of rainfall infiltration and analysis of slope stability mechanism.In this study,we used the representative “Jiwachang landslide” that occurred on the south side of Bahe River in the Bailu tableland as a research case and conducted infiltration experiments on the undisturbed loess-paleosol sequences(L-PSs),the prior landslide body(PLB)and the new landslide body(NLB).We measured the soil physical property indexs in the laboratory.Based on experiments and surveys in the field,we observe the following:(1)The results of double-cylinder permeameter show that all the infiltration curve of experiments exhibit the tendency of decreasing infiltration rate as the infiltration time increases.The matching results of Horton formula,Kostiakov formula and General experience formula show that these formula not only applied to describe the law of undisturbed soil,but also applied to represent the law of disturbed soil.(2)The wetting front form of L1,L2 and PLB almost show a shape of parabola.While the wetting front of S1 is not bilateral symmetry because the calcareous concretion.The depth of wetting front exhibits a tread of L1>PLB>S1>L2.We measured the soil water content and saturability found that the water content and saturability significantly increased during the wetting front after the infiltration experiments.(3)According to the experiment results of the single-cylinder permeameter,the initial infiltration rate(IIR)of UDS,PLB and NLB exhibits a tread of UDS<PLB<NLB.The IIR of NLB was greatly increased compared with UDS and PLB,while the UDS and PLB were not show notably difference on QIR.The difference of bulk density and porosity not have significantly influence in the IIR of NLB,but the infiltration rate of UDS and PLB.(4)According to the results of the Reformed Dynamic Cone Penetration experiment,the UDS have greatly homogeneity,the compactness of UDS shows the tendency of increasing slowly with the increase of depth.There are significant differences in the density of soil in different parts of the PLB.The compactness of NLB shows the tendency of Upper part>Middle part>Lower part.(5)The fissures are the dominant pathways for the infiltration of water,the main reason for the substantial increase in the IIR for the NLB is that the soil of the NLB was severely disturbed with evidence of a loose soil structure.Because of the role of snowfall,rainfall and compaction,the surface of NLB formed distinct structural soil crusts(SSCS)during 3~5 months with the thickness of 0.5~2cm.The IIR of NLB was only 9.4 mm/min with SSCS.The results of infiltration experiment showed that the appearance of SSCS and compaction were the main reason of the IIR of NLB drapped down significantly.