岩溶地区桩基础施工技术及泥浆护壁机理  

Bored Pile Installation Method and Slurry Borehole Protection Mechanism in Karst Terrains

作　　者：顾浩然 庞冬伟 GU Haoran;PANG Dongwei(Zhongji Construction and Exploration Group Co.Ltd.,Shijiazhuang 550081)

机构地区：[1]中冀建勘集团有限公司,石家庄550081

出　　处：《土工基础》2024年第2期215-219,共5页Soil Engineering and Foundation

摘　　要：为解决强岩溶发育地区旋挖桩成孔过程中的塌孔、偏斜、埋钻等问题,以某高层小区桩基础施工为研究对象,在分析场区岩溶工程地质特征的基础上,采用现场实测与理论分析的方法,针对施工中易发的钻孔偏斜和卡钻、土岩交界面塌孔、溶洞充填物塌孔三类风险问题,提出了双钢护筒工艺以及泥浆护壁方法,并解释了泥浆护壁的力学机理。研究结果表明,场区岩溶特征主要为存在竖向发育的裂隙、不规则充填、半充填和全充填溶洞,钻孔见洞率达到50%,各钻孔线溶率范围45%~78%。针对钻孔偏斜和卡钻问题,对不同土层和岩层提出了钻进给进力、钻速和钻进率3个控制参数要求;针对钻孔土岩交界面塌孔问题,提出了双钢护筒工艺,并采用大锥角、耐磨蚀的螺旋钻头对岩面进行修正;针对溶洞充填物塌孔问题,提出注浆加固与泥浆护壁的措施,在优选的泥浆中加入思洛瑞(slurry)聚合物0.573 kg后,可以有效改善泥浆的护壁效果,降低漏浆、塌孔、埋钻和缩径等事故发生。To resolve the problems of the borehole caving,deflection,and lost drill bit during the drilling process of the rotary excavation of bore piles in well-developed karst terrains,this paper presents a case history of bored pile installation for a high-rise residential building.Based on the analysis of the geological characteristics of the karst terrain at the site,the common in-stallation hazards occurred in the bored pile installation in the karst area,such as,borehole out of plumbness,drill bit jam,borehole caving at the soil-rock interface and in the flling material,could be mitigated throughout double casing method as well as slurry borehole protection.The results show that the main characteristics of the karst terrain at the project site are the pres-ence of vertically developed fractures,irregular filling,semi filled,and fully filled karst rock cavities and pinnacles.In rock cavities in the borehole during the drilling out of plumbness and the advancement reach 5o%,and the linear dissolution rate of each borehole ranges from 45%to 78%.For the problem of drilling out of plumbness and drill bit jam,three control parame-ters,namely,drilling downward pressure,rotational speed,and drilling rate,are proposed for different soil layers and rock formations.For the problem of borehole caving at the soil rock interface,the double steel casing method was proposed,and a large cone angle,wear resistant spiral drill bit was used for advancing near the rock surface.For the problem of caving in the filling material,measures for grouting improvement and slurry borehole protection are proposed.After adding of O.573kg spe-cial polymer slurry into the borehole can effectively improve the borehole wall stability and reduce hazards such as slurry lost,borehole caving,drill bit lost,and borehole necking.

关 键 词：岩溶地区 桩基础 泥浆护壁 线溶率 充填物 溶洞处理 力学机理 

分 类 号：TU473[建筑科学—结构工程]