铀罐基础病害事故的分析

Analysis on the Accident of Unhealthy Tank Foundations

大港地区某油库的4座油罐发生了倾斜事故,罐区的土层是以粘性土为主的第四系松软沉积物,特点是强度低、结构稳定性差、松软易扰动、渗透性差。分析了罐区基础倾斜的原因,①对软基础处理不当,未采取措施改善地基土的排水条件,②忽视了加荷速率与充水速度的控制,致使施加的荷载超过了地基承载能力,③施工中破坏地表层结构等问题。对罐基础补救的最佳措施是采用高压旋喷注浆法,可有效地解决罐基础的继续下沉及罐心大锅底扩大和倾斜问题。为保证软地基土油罐的安全使用,需要对软基础合理处理,即根据地基持力压缩层的工程特性决定加荷充水速率的大小;由油罐特性、荷载分布特性决定采用天然地基、筏片基础、砂桩等相应的基础方式;油罐基础间应设计有沉降的安全距离。

Four tanks in a tank farm in Dagang area had an inclination problem. The soil in this area is soft Quaternary sediment mainly consisting of clay, which is featured by low intensity, unstable structure,logh softness and pertubility, and poor permeability. The following reasions for foundation inclination are analyzed : ①The soft foundation was not properly prepared, and measures for drainage improvement were not taken;②The active load exceeded the foundation bearing capacity due to the fact that the control of loading rate and water filling rate had been ignored ;③The surface structure was destructed during construction. The best remedy to tank foundation is rotary cement injection with high pressure which can effectively prevent further foundation settlement .enlargement of the 'kettle bottom' and inclination development. For the purpose of safe operation, the soft foundation shall be improved using the follow methods: specify loading and water filling rate according to engineering characteristics of bearing compression layer of the foundation; use natural, raft or sand pile foundation depending upon the tank features and load distribution; and design a safe distance between foundations for settlement.