含水率影响下全风化泥质灰岩工程地质特性及桩孔稳定性分析

Engineering geological characteristics of completely weathered argillaceous limestone under the influence of water content and analysis of pile hole stability

全风化泥质灰岩成分复杂、结构特殊,遇水易软化崩解,强度迅速降低,极易诱发多种工程地质灾害。以济南大涧沟地区全风化泥质灰岩为研究对象,通过现场勘察与室内试验相结合,从物理、力学和水理等方面研究了全风化泥质灰岩的工程地质特性,并基于PFC离散元软件对钻进过程孔壁稳定性进行评价,得到钻孔孔内应力与灌浆压力间的相关关系,为今后桩基施工提供合理的建议和参考。研究结果表明:全风化泥质灰岩耐水性差、易崩解,且含水率对崩解速率影响尤为显著;随着含水率升高,全风化泥质灰岩抗剪强度呈指数函数趋势减小,强度损伤劣化规律明显;在动态扰动下全风化泥质灰岩内部单元损伤严重,建议将泥浆压力设定为0.3 MP,可在不造成土层破坏的前提下对孔壁生成较为明显的法向接触力,为孔壁的稳定提供较好的支撑。

Completely weathered argillaceous limestone has complex composition and special structure.When countered water,it is easy to be soften and distingrate,and its strength is rapidly reduced,which is very easy to induce various engineering geological disasters.Taking the completely weathered argillaceous limestone in Dajiangou area of Jinan as the research object,the engineering geological characteristics of the completely weathered argillaceous limestone are studied from the physical,mechanical and hydraulic aspects through the combination of field investigation and laboratory test,moreover,the stability of the hole wall during the drilling process is evaluated based on the discrete element software PFC.The correlation between the stress in the hole and the grouting pressure is obtained,which provides reasonable suggestions and references for the future pile foundation construction.The results show that the completely weathered argillaceous limestone has poor water resistance and is easy to disintegrate,and the water content has a significant impact on the disintegration rate.With the increase of water content,the shear strength of completely weathered argillaceous limestone decreases exponentially,and the deterioration of strength is obvious.Under dynamic disturbance,the internal unit of completely weathered argillaceous limestone is seriously damaged.It is recommended to set the mud pressure at 0.3MP,which can generate relatively obvious normal contact force on the hole wall without causing soil damage,and provide better support for the stability of the hole wall.