岩溶地区地基处理及基础设计方法探讨  

Discussion on ground treatment and foundation design method in karst area

作　　者：李国胜 Li Guosheng(Tongling Construction Engineering Drawing Design Review C o.,Ltd.,Tongling 244000,China;Tongling Construction Engineering Quality Supervision and Monitoring C o.,Ltd.,Tongling 244000,China)

机构地区：[1]铜陵市建筑工程施工图设计文件审查有限公司,铜陵244000 [2]铜陵市建设工程质量监督监测有限公司,铜陵244000

出　　处：《建筑结构》2020年第3期119-128,共10页Building Structure

摘　　要：针对岩溶地区溶洞和土洞的特点,总结其基础设计方法和土洞及表层(或浅层)岩溶的处理方法。当满足《建筑地基基础设计规范》(GB 50007-2011)第6.6.6条规定时,可不考虑岩溶对地基稳定性的影响。当岩溶以上有厚度较大、承载力较高的覆土,且岩溶稳定、基岩顶标高总体基本相同时,可采用整体性较好的筏基和箱基。对于高度较大的高层建筑,覆土承载力不满足时,可采用CFG桩等刚性桩复合地基进行处理;当覆土承载力较低时,可采用人工挖孔桩、冲击成孔灌注桩或旋挖桩,不能采用管桩或其他预制桩。采用桩基时,应保证桩端以下3倍直径且不小于5m深度范围内无土洞、溶洞、破碎带或软弱夹层等不良地质条件。对《建筑地基基础设计规范》(GB 50007-2011)第8.5.6条第6款规定的"桩底应力扩散范围内应无岩体临空面"的规定,可根据具体工程的覆土厚度、临空面坡度和软弱面倾斜方向等,分析其影响程度;不是所有临空面都影响地基稳定。嵌岩桩承载力大多由桩身混凝土强度控制,应重视桩身强度验算和桩身完整性检测。Aiming at the characteristics of karst caves and soil caves in karst area, the foundation design methods and the treatment methods of soil caves and surface(or shallow) karsts were summarized. When meeting the requirements of article 6.6.6 of Code for design of building foundation(GB 50007-2011), the influence of karst on the stability of the foundation can be neglected. The raft foundation and box foundation with good integrity can be used when there is a covering soil with large thickness and high bearing capacity above the karst and the karst is stable and the elevation of the bedrock top is basically the same. For high-rise buildings with large height, rigid pile composite foundation such as CFG pile can be used for treatment if the bearing capacity of the covering soil is not satisfied;if the bearing capacity of the covering soil is low, manual hole digging pile, percussive bored pile or rotary excavation pile can be used instead of pipe pile or other prefabricated piles. When pile foundation is adopted, it shall be ensured that there is no adverse geological conditions such as soil cave, karst cave, broken zone or weak interlayer within the range of 3 times of diameter and not less than 5 m depth below the pile end. According to the provisions of clause 6, article 8.5.6 of Code for design of building foundation(GB 50007-2011), there shall be no free surface of rock mass within the stress diffusion range at the pile bottom, so the influence degree can be analyzed according to the thickness of covering soil, the slope of free surface and the inclined direction of weak face;not all free surfaces affect the stability of the ground. The bearing capacity of rock socketed pile is mostly controlled by the concrete strength of the pile shaft, so it is necessary to pay attention to the checking calculation of pile shaft strength and the integrity detection of the pile shaft.

关 键 词：岩溶 溶洞 土洞 临空面 基础形式 桩基 嵌岩深度 超前钻 

分 类 号：TU470[建筑科学—结构工程]