【作者】 赵宇；

【导师】 侯和涛；

【作者基本信息】 山东大学 ， 建筑与土木工程， 2021， 硕士

【摘要】 桩基础因其形式多样,承载力高,可用于复杂地质条件等特点,在建筑领域中的应用日益广泛。而螺旋钢桩作为一种新型变截面桩,具有施工周期短、绿色环保、对场地要求较少、承载力较高等诸多优点。近年来,螺旋钢桩的应用领域不断拓宽,在民用建筑、桥梁基础、路基建设、建筑基础加固中都有其运用的场景。然而目前对于螺旋桩安装后桩周土体强度损失与恢复的研究工作还相对缺乏,设计理论还不够成熟。本文通过静载试验和有限元数值模拟两种研究方法,对螺旋钢桩旋入土体后的抗压承载力和计算方法进行研究,主要研究螺旋桩桩身设计参数、注浆前后桩周土强度对其抗压极限承载能力的影响。得到的研究成果如下:(1)根据静载试验,分别对螺旋桩注浆情况和叶片疏密进行研究。通过荷载位移曲线判断螺旋桩竖向极限承载能力大小。表明注浆可以显著提高螺旋钢管桩极限承载力;叶片数目增多后会在土体中形成多个位移面,导致荷载位移曲线较早进入过度的非线性段,而且破坏后土体的残余强度较少。(2)对试验数据进行数值模拟分析。在到达极限抗压承载力后,与未注浆相比注浆后的螺旋钢管桩桩身螺旋叶片下的承载力系数是未注浆的1.6～2.0倍,为10.0～11.0;桩端和桩端附近的螺旋叶片承载系数是未注浆的2.9～2.3倍,为28～31;破坏面土体强度是原土体强度的120%～160%。(3)对注浆式螺旋桩的叶片大小、桩端附近叶片与桩端的距离和注浆后叶片厚度进行数值模拟分析。表明注浆式螺旋钢管桩的破坏方式是圆柱形剪切破坏,破坏面集中在叶片下方土体和桩周附近土体的接触区域。(4)综合试验研究结果,对原有的螺旋钢管桩极限承载力公式进行改进,从而得到注浆式螺旋钢管桩的极限承载能力计算公式,并与试验结果和数值计算结果进行比对,验证了公式的准确性。更多还原

【Abstract】 Because of its various forms,high bearing capacity,and its ability to be used in complex geological conditions,pile foundations have become increasingly widely used in the field of construction.As a new type of different pile,helical pile has many advantages,such as short construction period,green environmental protection,less site requirements and higher bearing capacity.In recent years,the application field of helical pile is constantly expanding,and it has its application scene in civil buildings,bridge foundation,subgrade construction,and building foundation reinforcement.However,the research on the soil strength loss and recovery around the pile after the installation of helical pile is relatively lack,and the design theory is not mature enough.In this paper,The vertical bearing performance and theoretical calculation of the helical pile after being screwed into the soil are studied,by both two methods,the pile static load test and the finite element numerical simulation.The main research is on the design parameters of spiral piles and the soil around the piles before and after grouting.The influence of strength on its ultimate compressive bearing capacity.The research results obtained are as follows:(1)According to the static load test,the grouting situation of the helical pile and the density of the helical plates are studied respectively.The vertical ultimate bearing capacity of helical pile is judged by the load displacement curve.The results show that grouting can significantly improve the ultimate bearing capacity of helical pile.when the number of plates increases,multiple displacement surfaces will be formed in the soil,causing the load-displacement curve to enter the excessively nonlinear section earlier,and the residual strength of the soil after failure less(2)Perform numerical simulation analysis on test data.After reaching the ultimate compressive bearing capacity,the bearing capacity factor under the helical plates of the helical pile after grouting is 1.6～2.0 times that of the ungrouting,which is 10.0～11.0;The load-bearing factor of the helical plate near the pile tip is 2.9-2.3 times that of ungrouting,which is 28-31;the strength of the damaged surface soil is 120%-160%of the original soil strength.(3)Numerical simulation analysis of the helical plate size of the grouting helical pile,the distance between the helical plate near the pile tip and the pile tip,and the helical plate thickness after grouting.It shows that the failure mode of the grouting helical pile is cylindrical shear model,and the failure surface is concentrated in the contact area between the soil under the helical plate and the soil around the pile.(4)Comprehensive test results,improve the original ultimate bearing capacity formula of helical piles,and obtain the ultimate bearing capacity calculation formula of grouting helical piles,and compare them with the test results and numerical calculation results,Verified the accuracy of the formula.更多还原