全风化花岗岩地区桥梁灌注桩成桩质量研究  

Study on Pile Quality of Bridge Cast-in-Place Pile in Completely Weathered Granite Area

作　　者：宋威 SONG Wei(China Railway Design Corporation,Tianjin 300308,China)

机构地区：[1]中国铁路设计集团有限公司,天津300308

出　　处：《铁道建筑技术》2023年第10期136-140,共5页Railway Construction Technology

基　　金：中国铁路设计集团有限公司科技开发课题项目(2021A230106)。

摘　　要：全风化花岗岩广泛分布于我国华南、西南地区,因其特殊的物理力学性质,目前针对全风化花岗岩地区地层工程特性和灌注桩成桩质量的研究较少。本文依托新建广州至湛江高速铁路桥梁试验桩工程,分别采用冲击锤法、旋挖干钻法和旋挖泥浆护壁法3种工艺成孔后对各灌注桩成孔质量进行分析对比,并在成桩后进行小应变测试以检验桩身质量。结果表明:旋挖干钻法施工简单、成孔速度快,桩长、桩径、桩底沉渣厚度等参数均能满足设计要求,成桩质量较为可靠;冲击锤法成孔速度慢,对全风化花岗岩层扰动过大,成孔孔径波动较大,孔内15 m以下频繁产生扩孔;旋挖泥浆护壁法无法保证全风化花岗岩结构稳定性,成桩过程存在缩径和塌孔现象,且桩底沉渣较厚,成孔质量较差。建议全风化花岗岩地区桥梁灌注桩施工应优先考虑旋挖干钻法。Completely weathered granite is widely distributed in southern and southwestern China.Due to its unique physical and mechanical properties,there is currently little research on the geological engineering characteristics and pile quality of cast-in-place piles in completely weathered granite areas.This article relied on the test pile engineering of the new Guangzhou-Zhanjiang high-speed railway bridge to analyze and compare the hole-forming quality of each cast-in-place piles after drilling by using three techniques:impact hammer method,rotary excavation dry drilling method,and rotary excavation mud wall protection method,and the quality of the pile body was inspected through small strain testing after the pile was formed.The results indicate that the rotary excavation dry drilling method is simple in construction,fast in drilling speed,and can meet the design requirements for parameters such as pile length,pile diameter,and pile bottom sediment thickness.The quality of the pile is relatively reliableꎻthe impact hammer method has a slow drilling speed and excessive disturbance to the completely weathered granite layer.The pore size fluctuates greatly,and frequent expansion occurs below 15 meters in the holeꎻthe rotary drilling mud wall protection method cannot ensure the stability of the completely weathered granite structure,and there are phenomena of shrinkage and hole collapse during the pile formation process.The sediment at the pile bottom is thick,and the quality of the hole formation is poor.It is recommended to prioritize the use of rotary excavation dry drilling method when constructing bridge cast-in-place piles in completely weathered granite areas.

关 键 词：全风化花岗岩 桥梁灌注桩 成孔工艺 成桩质量 

分 类 号：U443.15[建筑科学—桥梁与隧道工程]