Development of Seepage-Type Detention Facilities for the Control of Urban Runoff

在本研究中，渗透型滞洪设施在城市水文中的作用得到了澄清。在此基础上，提出了考虑多层地下结构组合的城市径流定量控制措施，建立了基于孔隙水动力学的非饱和入渗机理理论模型。建立了均匀管和变截面管的毛细管模型，推导了渗透率随含水率的变化关系，以及渗透率与压力势的关系。理论计算结果与已有的实测结果或经验公式吻合较好，并对一个包括渠道、滞洪设施和透水管网的防洪工程进行了综合分析。结果表明，削减洪峰流量和缩短洪峰时间是通过管网和明渠的蓄水作用实现的。当我们建造渗透区或补给区远离河道时，没有观察到地下水径流量的明显增加。在高原地区修建快干基质对减少地表径流和地下径流的洪峰流量是有效的，通过现场观测，估算了沟道和透水路面的入渗能力。一个数学模拟再现良好的协议与观测结果。

In the present study the role of infiltration-type detention facilities in urban hydrology was clarified. Furthermore, a quantitative and controlling measure was derived for urban runoff considering a combination of multi-layer subsurface structures.A theoretical model for the mechanics of unsaturated infiltration was developed based on hydrodynamics of water column in pores. A capillary model of uniform tube or varying-section tube was formulated which resulted in a theoretical derivation of permeability as a function of moisture content and a relationship between permeability and pressure potential. Theoretical estimation agreed quite well with existing observed results or empirical formulae.Flood control measures by the improvement of subsurface structures were comprehensively analyzed for a network which included channels, detention facilities, and pervious pipe networks. It is shown that the reduction of peak discharge and time to peak is accomplished by the storage effect in pipe network and open channels. When we construct infiltration area or recharge area away from river channels, no appreciable increase was observed in groundwater runoff. It is also found out that the construction of fast drying substrata in a plateau area is effective to reduce thepeak discharge both in surface runoff and groundwater runoff.Capacity of infiltration was estimated for a trench and a pervious pavement through field observation. A mathematical simulation reproduced good agreement with observed results.