Interrelationship Analysis Of Formation Properties And Water Storage And Drainage Function In Construction Of Sponge City

The construction of sponge city is to solve the problems in city development such as comprehensive utilization of rainwater and surface water resources, urban drainage and flood control and ecological environment protection. This is also an important way to realize low impact development which has important signifi-cance in solving the resources and environmental problems such as urban water shortage and waterlogging and to achieve the sustainable development of city.The demonstration project of sponge city construction has been started in our country. Due to the difference in topography, engineering geology, hydrology ge-ology, surface water and meteorological conditions in various cities, so that the focus should be changed with the cities. Beijing is a city of water shortage and waterlogging, while water shortage is much more serious. Based on the back-ground of sponge city construction in Beijing central areas, research on the influ-ence mechanism of soil physical and mechanical parameters on water storage and drainage function of formations was carried out. A new idea for sponge city con-struction was proposed by utilizing soil strata to conduct the rainwater collection and storage, and the specific way is to transform hard surfacing to allow rainwater to seep into the strata and build recharge well to import rainwater into aquifer with the use of natural resources as much as possible at the same time. And the influ-ence mechanism of soil parameters on water storage and drainage of strata was analyzed and revealed. The main work and conclusions were as following:(1) The idea of sponge city construction in Beijing center area was put for-ward based on the evaluation of population distribution, land value, meteorologi-cal conditions, geological conditions, rainwater quality of the central area of Bei-jing and the reference of the existing way of rainwater utilization and the combi-nation with the actual situation of the central area of Beijing. Focus should be paid on the hard surfacing transformation of pedestrian trails, parks and parking lots to allow rainwater to seep into the strata and the build of recharge well to import rainwater into aquifer with the use of natural resources as much as possible at the same time under the actual situation of Beijing center area. The natural strata should be fully utlized for water storage, and it will reduce the construction of the sponge city facilities.(2) Consolidation analytical expression of soft soil fromation was deduced in the process of aquifer water level decline with the upper building load, and soft soil consolidation behavior under correlation parameter variation was analyzed according to the analytical solution of the consolidation. The influence mecha-nism of the related physical and mechanical parameters on the consolidation set-tlement of soft soil fromation caused by declining aquifer water level was re-vealed, which provides the theoretical basis for the calculation of fromation drainage threshold.(3)The formula of radial velocity and radial displacement of the surface soil layer were deduced when the rainfall permeates into soil, the formula of radial velocity and radial displacement of the skeleton particles in the aquifer were ob-tained when the water was poured into the confined aquifer. The influence mech-anism of the related physical and mechanical parameters on the horizontal dis-placement of the soil caused by the water storage was revealed, which provides the theoretical basis for the calculation of sponge water saving threshold.(4) Sensitivity analysis of soil parameters that affects the function of water storage and drainage of strata was conducted based on grey correlation analysis method, and the influence weights were determined and ordered, the soil physical and mechanical parameters which need to be emphatically analyzed during the transformation of hard surfacing and recharge well construction were determined. A new method for determining the resolution coefficient in the grey correlation analysis method was proposed, and the rationality and validity of the method was verified with two examples.(5) The physical and mechanical process of strata drainage and storage were simulated by FLAC3D, and the influence of soil parameters on the process of strata drainage and storage were analyzed and evaluated. The variation rules of for-mation in water storage and drainage were obtained, and the theoretical analysis and calculation results of formation drainage and storage were verified as well.