砂土地基中静压桩桩体回弹和复压特性分析  

Analysis of rebound and recompression characteristics of jacked piles in a sand foundation

作　　者：刘海军 肖昭然[1] 赵宪强 赵文才 吕清显 LIU Haijun;XIAO Zhaoran;ZHAO Xianqiang;ZHAO Wencai;Lü Qingxian(College of Civil Engineering and Architecture,Henan University of Technology,Zhengzhou 450001,China;Geotechnical Engineering Department,Nanjing Hydraulic Research Institute,Nanjing 210024,China;College of Civil and Transportation Engineering,Hohai University,Nanjing 210024,China;Henan Jianke Foundation Engineering Co.,Limited,Zhengzhou 450000,China;China Railway Construction Group Co.,Ltd,Beijing 100040,China)

机构地区：[1]河南工业大学土木工程(建筑)学院,河南郑州450001 [2]南京水利科学研究院岩土工程研究所,江苏南京210024 [3]河海大学土木与交通学院,江苏南京210024 [4]河南省建科基础工程有限公司,河南郑州450000 [5]中铁建设集团有限公司,北京100040

出　　处：《建筑结构学报》2022年第7期301-310,共10页Journal of Building Structures

基　　金：国家自然科学基金项目(50978086,51178165)。

摘　　要：明确静压桩回弹和复压特性有利于提高静压沉桩质量及其经济性。为此,采用室内模型试验模拟砂土地基中静压沉桩,考虑沉桩速率、桩长和卸荷速率,分析静压桩卸荷过程中桩体回弹量、桩周侧压应力、桩端残余应力和单桩极限承载力的变化规律。并对比分析了复压前与复压后桩体回弹量、桩周侧压应力和桩体极限承载力的变化。结果表明:桩体回弹量主要与桩长有关,桩体回弹量约为桩长的0.4%,并随沉桩速率和卸荷速率增加而增大,且卸荷速率的影响程度大于沉桩速率。建立了桩体回弹量随时间变化的双曲线模型,较好地反映了卸荷过程中桩体回弹量随时间的变化规律。提出了卸荷后桩周侧压应力计算的修正被动土压力计算式,其计算结果显著优于被动土压力公式计算结果。沉桩速率和卸荷速率引起的极限承载力差异最高可达12%,建议以沉桩终压力的1.04倍进行桩体极限承载力估算。复压的主要作用是提高桩周侧压应力,且桩周侧压应力约提高50%,桩体承载力提高幅度约为10%,故实际工程中应关注复压施工质量,以有效提高桩体极限承载力。It is conducive to improve the quality and economy of jacked piles by clarifying the influences of the rebound and recompression characteristics of jacked pile.;The model test was used to simulate jacked piles in a sand foundation,considering the jacking speed,pile length and unloading speed.The variation law of the following parameters was analyzed:the pile rebound,the radial stress of the soil surrounding the pile,the residual stress of the pile tip and the ultimate bearing capacity of the pile.To clarify the mechanism of recompression of jacked piles,analysis was conducted on the variation law of the pile rebound,the radial stress of the soil surrounding the pile,the residual stress of the pile tip and the ultimate bearing capacity of the pile before and after the recompression.The experimental results show that the pile rebound is mainly related to the pile length,and the rebound of the pile is about 0.4%of pile length.The pile rebound is increased by the increase of the jacking speed and unloading speed.The effect of the unloading speed is larger than the jacking speed.A hyperbolic model was established on the variation of pile rebound over time,and the model was verified by the experimental results.The modified passive earth pressure formula for the calculation of the lateral pressure over the circumference of the pile after unloading is proposed,and the result is obviously better than the passive earth pressure.Meanwhile,the difference of ultimate bearing capacity of piles is affected by the jacking speed and the unloading speed is up to about 12%.It is suggested to use 1.04 times of the final pressure of the sinking pile to estimate the ultimate bearing capacity of the pile.The lateral pressure of the pile body is improved by the recompression.The lateral pressure of the pile body increases by about 1.5 times on average.The ultimate bearing capacity of the pile can increase by about 10%by recompression.Therefore,the quality of the recompression construction should be paid attention to in actual projects i

关 键 词：静压桩 桩体回弹 模型试验 复压特性 承载力特性 桩周侧压应力 

分 类 号：TU473[建筑科学—结构工程] TU317.1[建筑科学—土工工程]