成都卵石地层渗透系数测定及降水方案设计

The Determination of Permeability Coefficient and Design of Dewatering Scheme of Gravel Foundation in Chengdu

渗透系数是基坑降水设计中的重要参数,而不同地质成因、粒径、充填物类型、密实度及风化程度的卵石地层渗透系数差异很大,因此,对特定场地可采用抽水以试验较准确地测定卵石层的渗透系数。勘察期间在场地周边凿井进行24h连续抽水试验,根据潜水完整井稳定流计算公式计算得出卵石层渗透系数理论值为11~13m/d。根据实测参数并结合工程经验,进行了基坑工程管井降水方案设计,降水井数量、深度布置合理,保证了基坑开挖及地基基础的正常施工。

Permeability coefficient is the key hydrological parameter of foundation pit dewatering design.Due to the difference of geological genesis,particle size,fillings type,density and weathering degree to permeability coefficient of gravel varies widely in different sites.As a result,permeability coefficient need to be determined accurately by pumping test in a specific engineering site.Two pumping well are constructed and24 hpumping test is conducted during investigation and surveying,and then permeability coefficient is determined as 11~13 m/d based on the test data according to the steady flow calculation formula for a complete diving well.Finally,according to the test result and engineering experience,the design of the foundation pit dewatering design for the tube wells is carried out.The number and depth of the dewatering wells are reasonably designed to ensure the foundation pit excavation and the normal construction of the foundation.