用超声波CT检测深桩基础压浆的分布与成形
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摘要
本文分析了在苏通长江大桥用超声波CT检测桩底压浆效果的实验研究和工程检测的过程与主要结果。理论和检验实践表明,超声波CT技术检测桩底压浆效果是可行的。在试验桩检测中解决了多项关键技术问题,检测结果显示了压入水泥浆分布范围的图像。结合试验桩其它检验结果,认为桩底压浆可以在桩底形成扩大头,提高桩的侧向摩擦阻力和桩端承载力,从而有效提高桩基础总体的承载力,这一结论支持了在苏通大桥应用桩底压浆技术的决策。实际工程桩检验结果证实了试验桩的判断,观测到水泥浆在桩底沿中粗砂层流动形成的加固层,达到了满意的成形效果。
According to the theoretical analysis,it was possible to check distribution of post grouting at the bottom of piles by ultrasonic CT.The testing check was done at first.Several technological difficulties in checking process were solved,such as the reliability and stability of instruction system,ultrasonic sign identify and correction,criterion for identifying different materials in the checking profile and its speed distribution figure.Since the materials in checked profile form several boundaries and lead complex reflection from refraction,the key in test checking was to identify arrive time correctly and build right criterion to link sonic wave velocity with materials.The results approved that the grouting at the bottom of piles could form a ball-liked end.The final shape of pile end after grouting depended on both ratio of cement grouting to sand and pressure and speed.The enlarged part at pile bottom increased the frictional resistance around piles and the bearing capacity at pile bottom,which effectively improved the bearing capacity of pile foundation.The results,together with those by bearing capacity tests,supported the decision of applying the post grouting technology.In a practical engineering at fundament of constructing Yangtze River Bridge in Nantong city,Jiangsu Province,it was observed at checking profile that the post grouting flowed along center coarse sand layers and a no bar concrete layer was formed.The shape of enforced region was satisfactory.
According to the theoretical analysis,it was possible to check distribution of post grouting at the bottom of piles by ultrasonic CT.The testing check was done at first.Several technological difficulties in checking process were solved,such as the reliability and stability of instruction system,ultrasonic sign identify and correction,criterion for identifying different materials in the checking profile and its speed distribution figure.Since the materials in checked profile form several boundaries and lead complex reflection from refraction,the key in test checking was to identify arrive time correctly and build right criterion to link sonic wave velocity with materials.The results approved that the grouting at the bottom of piles could form a ball-liked end.The final shape of pile end after grouting depended on both ratio of cement grouting to sand and pressure and speed.The enlarged part at pile bottom increased the frictional resistance around piles and the bearing capacity at pile bottom,which effectively improved the bearing capacity of pile foundation.The results,together with those by bearing capacity tests,supported the decision of applying the post grouting technology.In a practical engineering at fundament of constructing Yangtze River Bridge in Nantong city,Jiangsu Province,it was observed at checking profile that the post grouting flowed along center coarse sand layers and a no bar concrete layer was formed.The shape of enforced region was satisfactory.
引文
[1]戴国亮,等.桩端后压浆桩压浆效果检测技术[J].施工技术,2005,1:74–76.(DAI Guo-liang,et al.Detection techn-ology for grouting effects of pile end post grouting piles[J].Construction Technology,2005,1:74–76.)
[2]李昌驭,等.钻孔灌注桩桩端后压浆机理及效果检测[J].工程质量,2005(2):6–49.(LI Chang-yu,et al.Mechanism and performance test of bored pile with post grouting at base[J].Engineering Quality,2005(2):46–49.)
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[4]刘红桂,等.井间超声波层析成像及其在岩溶勘察中的应用[J].地震学报,2003,25(4):415–421.(LIU Hong-gui,et al.Cross hole ultrasonic tomography and its application in karst development[J].ACTA Seismologica SINICA,2003,25(4):415–421.)
[5]刘良琼,等.井间地震射线走时层析成像数值模拟[J].工程地球物理学报,2004,11(15):441–446.(LIU Liang-qong,et al.The numerical simulation of cross hole seismic travel time computerized tomography[J].Chinese Journal of Engineering Geophysics,2004,11(15):441–446.)
[2]李昌驭,等.钻孔灌注桩桩端后压浆机理及效果检测[J].工程质量,2005(2):6–49.(LI Chang-yu,et al.Mechanism and performance test of bored pile with post grouting at base[J].Engineering Quality,2005(2):46–49.)
[3]王五平,等.声波CT检测钻孔灌注桩内部质量[J].施工技术,2000,10:26–28.(WANG Wu-ping,et al.Detection technology for grouting effects of pile end post grouting piles[J].Construction Technology,2000,10:26–28.)
[4]刘红桂,等.井间超声波层析成像及其在岩溶勘察中的应用[J].地震学报,2003,25(4):415–421.(LIU Hong-gui,et al.Cross hole ultrasonic tomography and its application in karst development[J].ACTA Seismologica SINICA,2003,25(4):415–421.)
[5]刘良琼,等.井间地震射线走时层析成像数值模拟[J].工程地球物理学报,2004,11(15):441–446.(LIU Liang-qong,et al.The numerical simulation of cross hole seismic travel time computerized tomography[J].Chinese Journal of Engineering Geophysics,2004,11(15):441–446.)
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