Study Of Polyacrylamide (PAM) Application For Controlling Colluvial Deposits Erosion Of Granite Collapsing Hill

The erosion of colluvial deposits is an important component of Collapsing hill, in the initial period of control, under the condition of heavy rainfall, the soil loss is enormous, which seriously affect the efficiency of biological measures. Therefore, there is important practical significance to look for a kind of chemistry measure for controlling the erosion rapidly. In this study, we take the granite colluvial deposits in Yang Keng Village of Longmen town in Anxi Country,Fujian Province for the target, through artificial simulation rainfall experiment, based on the select of suitable polyacrylamide(PAM), the study analysed the effect of five different application rate(which were1g/m2,2g/m2,3g/m2,4g/m2and6g/m2) on soil erosion and runoff of colluvial deposits under three different rainfall intensity(58mm/h,87mm/h,108mm/h),aim to choose the suitable PAM and its best application rate. The main conclusions are as follows:(1) PAMs different in molecular weight (MW)(8×106,12×106and15×106Da) and hydrolysis degree (10%,20%,30%) had a certain effect on soil erosion and runoff, the higher the molecular weight and hydrolysis degree was, the price of PAM increased. Considering the price of PAMs and the effect of erosion resistance, the PAM10%in hydrolysis of12x106Da molecular weight was more suitable for application in colluvial deposits of Collapsing hill. The aqueous solution applied is the best way of application for its ease of handing.(2) The soil structure of colluvial deposits is bad and lack of dispersible clay particles. The application of PAM on the soil surface leads the presence of artificial crusts which decrease the infiltration, increase the runoff and runoff rate. Under the condition of moderate, heavy and hard rainfall intensity, the runoff raised along with the improve of PAM application rate.(3)PAM could effectively improve the erosion resistance of colluvial deposits soil, compared with the CK, the five application rate all could reduce the soil loss under all the three rainfall intensity, whereas the impact of PAM exits a threshold, when the application rate exceeded the threshold, although the soil loss increased significantly, the effect was reducing. When the application rate of PAM was2-3g/m, the effect of decreasing soil erosion was the most significant, which could reduce the soil erosion most as much as50.12,82.29and66.66percent respectively under the condition of moderate, heavy and hard rainfall intensity.(4) All the PAM application rate affected the content of eroded sediment particles, the percentage of sand-sized particles increased, whereas the fraction of silt-sized and clay-sized particles decreased under all three rainfall intensity. PAM has a strong cohesive impact on silt and clay particles, when the application rate of PAM was2g/m2, both the silt and clay particles loss were the least.