Study On Soil Erosion And Countermeasures Of Dreg Fields Of The Water Conservancy Project In The North Side Of Tianshan Mountains

This thesis takes Daxigou Water conservancy project's dreg fields in the north side of Tianshan Mountains as a example, analyzes earth and rock balancing and planning based on engineering design proposal, makes a prediction calculation about the amount of dregs yielded by the project. The AutoCAD,Excel software and some mathematics methods were employed to analyze appropriate height and range of dregs and preferable stacking patterns, and estimate the surface area of dreg stacks.Two conventional methods were applied to monitor water and soil erosion in dreg fields,which are volume method and the peg method. Based on the monitoring outcome, some soil erosion features were analyzed and the amount of erosion was calculated, the soil erosion annual modulus during construction period were given, which can be a reference to evaluate and govern the soil erosion for related department. In addition, measure system of soil and water conservation and management ways were raised. The mostly conclusion is as below:According to the topography characteristics of selected dreg fields, considering the factors such as flood discharge function,capacity,stability of stacking,the convenience of transport and operation,the economic and feasibility of conservation measures and land restoration and utilization at late stage, the mode filling the ditch flat and building new drains could be selected to stack the dregs. The 15m height and 2000m length is rational range for dregs. The surface area corresponding is 2.4×105m2.Water erosion distribution is imbalance in time. Great amount erosion occurs in June to August which notablely beyond other months.During monitoring period, surface erosion occupys 29.9% and gully erosion holds 70.1% to the total amount. The ratio of the two forms is 3:7.At the beginning of erosion, thin gully erosion takes great amount about 50% of the total gully erosion. With the increasing of rainfall, distinct erosion gully formed, thin gully erosion amount reduced remarkably.The total annual water erosion modulus is 9097.15 t·km-2·a-1 and the whole amount of water erosion is about 4174.53t after discarding dregs. Among this,3761.13t is created by the disturbing and the rest is original erosion in this area. The amount of soil erosion caused by discarding dregs during construction period of this project is extremely serious.Taking the principle that obstructing before discarding, scientific and effective measures of water and soil conservation should be taken to prevent serious erosion for this ditch dreg field, such as gravity type of retaining wall,drainage system on the top and some vegetation ways, which also can improve the environment of dreg field. Global thought should be taken to adopt measures for preventing and controling soil erosion at all time.Taking preventing and controlling actions that suit local circumstances, making operators' duty clear, all these enable dreg field achieve efficient controlling and management.