Technology About Rainwater Seepage Wells And Technology About Diversion Of Rainwater And Sewage In Historic Block

The narrow streets and lanes in historic districts mainly adopt interception combined drainage system.After rainfall,mixed sewage overflows frequently,which causes great pollution to water environment.In order to reduce the pollution of overflow sewage,on the one hand,sponge technology should be used to reduce rainfall runoflf,on the other hand,rain and sewage diversion transformation should be carried out.Because of dense buildings and narrow roadways in historic blocks,it is difficult to implement sponge technology and rain and sewage diversion.In view of the characteristics of rubble soil in the underlying layer of Yangzhou historic blocks,this paper studies the decentralized sponge technology with courtyard seepage wells as the core to reduce rainwater runoff,and rationally arranges pipelines for narrow streets to realize the transformation of rainwater and sewage diversion in historic blocks.Specifically,the following work has been carried out:(1)On-site sampling analysis and study of the characteristics of debris particles and water infiltration capacity in the old urban area of Yangzhou.The thickness of the underground debris layer in the old urban area of Yangzhou is about 3m,which is a mixture of debris and clay.The particle size of debris is mainly 10mm～100mm.The particle size of clay is mainly 1.35m～32m.The average ratio of debris to clay is 1:3.The permeability of the underground debris layer is good.The average gravity water storage rate and permeability coefficient of the debris layer are 33.52L/m 3 and 13.490m/d～which are 7.7 times and 245.3 times of the original soil.Underground debris layer is not homogeneous distribution,but alternately exists strong and weak water conduction parts,forming oblique water conduction layer,forming a through water seepage channel.Because there is a large amount of clay on the surface of the old urban area,which affects the seepage of surface rainwater runoff,it is necessary to transfer the seepage surface from the surface to the underground debris layer with good permeability through seepage wells to strengthen the seepage of rainwater runoff.(2)The main architectural form of Yangzhou historic district is courtyard house.The runoff reduction model based on seepage well is established.The seepage well storage capacity was obtained and the seepage well schemes were determined for different courtyard.The experimental results show that the seepage flow can reach 3.36m3/h when the diameter of the seepage well is 1.65m and the water level in the well is 0.9m.The typical courtyard with a catchment area of 120m2 and a seepage well with a diameter of 1.6m were adopted,which could reduce the designed rainstorm runoff with a recurrence period of 3 years and rainfall duration of 120min by 89,27%.(3)For a typical historical block,the effect of reducing the difficulty of rainwater and sewage diversion under the model of seepage well about reducing rainfall and runoff was studied.The results show that the rainfall runoff can be reduced by about 50%under the model of seepage well about reducing rainfall runoff.In this mode,the designed storm water pipe diameter can be reduced by one or two grades compared with the conventional design.In addition,for the existing intercepting confluence drainage system,adopting the model of seepage well about reducing rainfall runoff can reduce the overflow of combined pipe by more than half under a recurrence period of 3 years,and effectively reduce the pollution of overflow mixed sewage to river.(4)The optimal design of rainwater and sewage diversion in narrow streets of historical blocks is carried out,and specific safety technical measures are put forward for each engineering pipeline to ensure that the horizontal net distance of each engineering pipeline can be reduced under the condition of safe operation.The layout of rainwater and sewage diversion in narrow streets with different widths was studied.According to the pipeline layout of special section in the historical block,the design of the upper and lower pipes of the same position of the rain water and sewage pipeline is proposed,and the design of the common inspection well of rain water and sewage is carried out,which provides an idea for realizing the separation of rain water and sewage in the narrow streets below 3m.At the same time,a new type of rain sewage pipeline is explored.A new concept that rainwater and sewage are double-layered together is creatively put forward,which provides a new idea for rainwater and sewage diversion in narrow streets.