Experimental Study On Rainfall Effect Of Lawn Greening Roof

As a modern comprehensive technology blending building techniques and garden art roof greening is a new greening way with development prospects in the urban construction. Roof greening not only plays a certain role in compensating green space,increasing air humidity,insulating sound,resisting pollution,freshen air and forming bioclimatic buffer layer in city;but also has good performance in retentioning and detentioning rainwater runoff quantity and quality by plant absorption and soil infiltration. To play better the function of rain interception,temperature control and air improvement,the selection of plants and growing medium is the key for roof greening technology. Due to special virescence condition, the planting substrate of roof greening has stricter requirements than common greening, the development of substrate with light weight, water retention and drainage capacity, sustainable utilization should be the study emphasis of roof greening techno logy. The main researches and conclusions are as follows in this paper:(1) The experiental study on growing media selection of lawn-style green roof.Based on the research status and analysis of functional effect of green roofs, considering lawn-style green roof,the experimental study on selection of nine media formulas which are composed of rural soil,coconut tree branny,vermiculite and pearlite is carried out. The optimal ratio of rural soil:coconut tree branny:vermiculite:pearlite=2:3:4:1is determined,then is rural soil: coconut tree branny:vermiculite:pearlite=2:4:3:1,though the measurement of their basic physicochemical properties and single pipe penetration test.Next analyzing the effect of dry density,total porosity of cultivation media on steady infiltration rate by Origin Software; screening nine media formulas by range method.(2)The influence of soil thickness on penetration performance. The average penetration rate and moisture accumulation osmotic quantity of soil will reduce to improve the rain interception with the increase of thickness, soil thickness and the average penetration rate show a good inverse linear relationship. Aiming at the particular rainfall retention demand,so it is feasible to choose the safe, efficient and appropriately thin planting media to meet roof load and plant growth requirements.(3)The impact analysis of dosage and layer thickness of super absorbent polymers on infiltration rate and accumulation infiltration amount in soil moisture one-dimensional vertical infiltration process.Water-keeping effect shows a irregular decrease trend with the dosage increase of Super Absorbent Polymers, the infiltration rate is lowest,when the dosage is1.5%or3.0%.The changes of infiltration rate,accumulation infiltration amount are regular with layer depth increase of SAP, the minimum and maximum penetration rate of soil appear respectively on layer depth of1cm and7cm. So the reasonable usage method is more meaningful than the dosage of SAP.(4) The rainfall duration and early drought time on seepage time and rainwater retention capacity of lawn-style green roof.Even though under the circumstances of thin layer and high soil moisture content of planting substrate, roof greening can achieve certain delay storage efficiencies, when SAP is added to the planting substrate of lawn-style green roof.Detention and retention simulation test of roof greening.Rainwater retention application of lawn-style green roof is impacted by rainfall intensity, rainfall duration and prophase drought time, the results show:rain delay storage efficiencies decrease with the rainfall intensity and duration increase of green roof and increase with prophase drought time lengthening.Rainfall duration and rainfall amount have consistent influence on rain delay storage efficiencies;the effect of prophase drought time on storage ratio relates to moisture content of soil mainly.