湘东北丘陵软岩区岩土工程勘察的常见技术问题及对策

Common Technical Problems and Countermeasures of Geotechnical Engineering Investigation in Hilly Soft Rock Area of Northeast hunan

湘东北中低山-丘陵区,分布着泥质粉砂岩、板岩等软质岩石,具有独特的工程特性。在岩土工程勘察中应采取针对性的技术对策提高勘察质量。分析讨论了工程勘察中的几个重点技术问题,针对破碎的风化层,宜采用双管取芯结合植物胶钻进工艺提高钻探质量;软质岩风化层厚度大,强、中风化层宜根据其岩体结构状态、抗压强度划分多个亚层,以充分发挥地基土的工程特性;软质岩中常有泥岩夹层,应重视其对缓倾角顺向坡的影响;设置排水盲沟或渗沟可降低地下水位,减少抗浮成本。

With special geotechnical properties,the soft bedrocks such as,muddy and silty sandstone and slate,are widely deposited in the regions of low hill and rolling hill of east Hunan Province.In this paper,several key technical points in the geotechnical investigations are analyzed and discussed.For the broken and strongly weathered layer,the double casing coring along with the vegetable jell as the drilling method should be adopted to improve the drilling quality;when the strongly weathered bedrock is thick,and it can be divided into several sub layers so that the detailed variation of the geotechnical characteristics in the rock mass can be captured.Mudstone lenses are frequently encountered in the soft bedrock and its influence on the stability of the day-lighted rock slopes should be fully investigated.Drainage ditches and French drains should be provided in order to reduce the groundwater level and minimize the cost for the buoyancy construction.