Research On Ecological Slope Protection Substrate Based On Dredged Silt Utilization

With the vigorous development of the river and lake dredging project in China,the amount of dredged silt is increasing,and the accumulation of silt not only causes waste of land resources,but also causes serious pollution to the environment.The reduction and harmless treatment of silt has become China’s urgent problem to be solved,the current resource utilization of dredged silt is the most promising silt treatment method.China is still in its infancy in the research of silt resource utilization.This paper combines the concept of resource utilization of dredged silt and the concept of ecological slope protection,and explores the feasibility of using dredged silt into the ecological slope protection substrate for resource utilization.This paper mainly studies the ecological effects and shear properties of the substrate.The main work is as follows:(1)By establishing a pot experiment model and selecting Bermudagrass as the experimental research object,and investigates the effects of substrate at different silt content(0,25%,50%,75%,100%)on the growth state of Bermudagrass.The results showed that the silt could increase the germination time of Bermudagrass 1~4d,which increased the germination rate of Bermudagrass,which was beneficial to the early germination of Bermudagrass.The silt could increase the stem length of Bermudagrass and increase the growth rate of Bermudagrass.The vegetation cover layer is formed faster,which improves the vegetation coverage and is conducive to soil and water conservation of the slope.When the amount of silt is 50%~75%,the best effect is that the silt promotes the growth of Bermudagrass.Under the other silt content,the growth promotion effect of the mud on the Bermudagrass is not maximized.When the amount is >75%,the promoting effect of silt on the budding time of Bermudagrass is significantly reduced.(2)Establish a substrate model of unplanted plants in the same manner as in(1)for on-site sampling,and direct shear test on samples under natural and saturated conditions at four different vertical pressures(50kPa,100 kPa,200kPa,300kPa).Exploring the effect of silt on the shear resistance of rootless soil under two conditions.The results show that for each 10% increase of silt content in the two states,the cohesive force of the soil in the natural state and the saturated state respectively by about 1kPa and 0.4kPa,the internal friction angle is reduced by about 0.41° and 0.26°,respectively.Under the same silt content,the cohesive force of the soil under saturated state is about 49% of the cohesive force in the natural state.The shear strength of soil under both conditions decreases with the increase of silt content,and the shear strength of soil decreases under saturated state is significantly smaller than the decrease of shear strength of soil under natural conditions..In general,the incorporation of silt will weaken the shear resistance of the soil to some extent.(3)Take the root-soil composite substrate sample in the substrate model of the planted plant by means of on-site sampling,and perform direct shear test on the root-soil composite substrate sample under natural state and saturated state,and combine(2)Analysis of the results of the research,the effects of silt on the shear resistance of the ecological slope protection substrate were investigated under the two conditions.The results showed that when the silt content was 0-50%,the root-soil composite substrate in two states was sticky.The cohesion increases with the increase of silt content,and the cohesive force of the substrate increases in saturation state is smaller than the increase of cohesion in the natural state;when the silt content is 50%~100%,the cohesive force of the root-soil composite substrate in both states decreases with the increase of silt content;the root system of Bermudagrass can increase the internal friction angle of the substrate to a certain extent.However,in general,the root system has little effect on the internal friction angle of the substrate,and the friction angle of the substrate decreases with the increase of the silt content in two states;50% is the optimum silt content,and the resistance of the root-soil composite substrate at this time The shear strength of the root-soil composite substrate with shear strength is significantly greater than that of other silts.The ability to enhance the protection of ecological slope protection system,illustrating the dredged silt ecological slope protection incorporated into the substrate resource utilization is feasible.