自平衡试桩法室内模型试验与现场测试对比研究
发布时间：2018-08-03 20:35
【摘要】：自平衡试桩法作为一种新兴的桩基检测技术在国内外得到了广泛的应用与发展,与传统试桩方法相比,该法省时、省力、占地面积小且不受测试场地限制。就该测试方法国内外主要研究自平衡上段桩桩侧摩阻力与传统静压桩、抗拔桩桩侧摩阻力的区别；平衡点位置的确定和自平衡测试后的试桩能否继续作为工程桩使用,但岩土性状复杂,自平衡法测桩仍有不少理论与实践问题。采用的方法包括理论分析、数值计算、现场测试,获得了许多宝贵的研究成果,本文采用花岗岩残积土为模型土对自平衡试桩法与传统试桩的极限承载能力和荷载传递方式进行了对比模型试验。在桩身外侧凹槽内粘贴电阻应变片从而可测得桩身随埋置深度不同的应变,得出相同边界条件下自平衡试桩与传统试桩桩侧摩阻力、桩身轴力的传递规律,从而揭示了花岗岩残积土中自平衡试桩法与传统静压试桩法的荷载传递规律与正负摩阻力之间的关系,并且结合实体工程进行了现场测试。取得了如下主要结论：(1)由于加载方式的不同,上托桩荷载自下而上传递,抗拔桩荷载自上而下传递,且传递的速率有所不同,上托桩荷载传递速率较抗拔桩小。(2)上托桩与抗拔桩桩侧摩阻力随深度分布不同,上托桩桩侧摩阻力在加载点位置承担了较大一部分,这是由局部增强效应所引起,而抗拔桩桩侧摩阻力分布较均匀,随着荷载的增加,抗拔桩下部土层比上托桩上部土层发挥的作用要大。(3)全风化花岗岩中桩侧正负摩阻力的修正系数γ可取0.5-0.6之间。(4)荷载达到极限值之前,施加荷载时加载点附近桩体受压径向膨胀,同时桩体带动桩周土位移,在桩端附近形成土拱,在上覆荷载作用下使得土拱效应使桩侧径向应力增加,桩侧摩阻力随之增加。(5)在全风化和强风化花岗岩土层中,利用砂土和碎石土的相关参数进行试验设计是可行的。
[Abstract]:Self-balanced pile testing technique has been widely used and developed at home and abroad as a new pile foundation testing technology. Compared with the traditional pile testing method, the method saves time and labor, occupies a small area and is not limited by the test site. This test method is mainly concerned with the difference between the lateral friction of the self-balanced pile and the traditional static pressure pile, the determination of the equilibrium point and whether the test pile can be used as the engineering pile after self-balancing test, and the difference between the friction resistance of the pile and the anti-uplift pile, the determination of the equilibrium point and whether the test pile can be used as the engineering pile after self-balancing test. However, the geotechnical properties are complex, and there are still many theoretical and practical problems in self-equilibrium pile measurement. The methods used include theoretical analysis, numerical calculation, field testing, and many valuable research results have been obtained. In this paper, granite residual soil is used as the model soil to compare the ultimate bearing capacity and load transfer mode between the self-balanced pile test method and the traditional pile test method. The strain of pile body with different buried depth can be measured by sticking resistance strain gauge in the outside groove of pile body, and the friction resistance of self-balanced pile and traditional pile under the same boundary condition can be obtained, and the transfer law of axial force of pile body can be obtained. The relationship between load transfer law and positive and negative frictional resistance of self-equilibrium pile test method and traditional static pressure pile test method in granite residual soil is revealed, and field test is carried out in combination with solid engineering. The main conclusions are as follows: (1) because of the different loading modes, the load is transferred from bottom to top, and the load of uplift pile is transferred from top to bottom, and the transfer rate is different. The load transfer rate of the upper pile is smaller than that of the uplift pile. (2) the lateral frictional resistance of the supporting pile is different from that of the uplift pile with the depth distribution, and the lateral friction of the supporting pile bears a large part at the loading point, which is caused by the local enhancement effect. However, the frictional resistance distribution of the anti-drawing pile is more uniform, and with the increase of load, (3) the correction coefficient 纬 of positive and negative frictional resistance of pile side in fully weathered granite can be between 0.5-0.6. (4) before the load reaches the limit value, When the load is applied, the pile body near the loading point expands radially under compression, while the pile body drives the soil displacement around the pile and forms a soil arch near the pile end. Under the overburden load, the soil arch effect increases the radial stress of the pile side. The pile side friction increases with it. (5) in the weathered and strongly weathered granite soil layers, it is feasible to use the relevant parameters of sand and gravel to carry out the experimental design.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1
本文编号：2162924
[Abstract]:Self-balanced pile testing technique has been widely used and developed at home and abroad as a new pile foundation testing technology. Compared with the traditional pile testing method, the method saves time and labor, occupies a small area and is not limited by the test site. This test method is mainly concerned with the difference between the lateral friction of the self-balanced pile and the traditional static pressure pile, the determination of the equilibrium point and whether the test pile can be used as the engineering pile after self-balancing test, and the difference between the friction resistance of the pile and the anti-uplift pile, the determination of the equilibrium point and whether the test pile can be used as the engineering pile after self-balancing test. However, the geotechnical properties are complex, and there are still many theoretical and practical problems in self-equilibrium pile measurement. The methods used include theoretical analysis, numerical calculation, field testing, and many valuable research results have been obtained. In this paper, granite residual soil is used as the model soil to compare the ultimate bearing capacity and load transfer mode between the self-balanced pile test method and the traditional pile test method. The strain of pile body with different buried depth can be measured by sticking resistance strain gauge in the outside groove of pile body, and the friction resistance of self-balanced pile and traditional pile under the same boundary condition can be obtained, and the transfer law of axial force of pile body can be obtained. The relationship between load transfer law and positive and negative frictional resistance of self-equilibrium pile test method and traditional static pressure pile test method in granite residual soil is revealed, and field test is carried out in combination with solid engineering. The main conclusions are as follows: (1) because of the different loading modes, the load is transferred from bottom to top, and the load of uplift pile is transferred from top to bottom, and the transfer rate is different. The load transfer rate of the upper pile is smaller than that of the uplift pile. (2) the lateral frictional resistance of the supporting pile is different from that of the uplift pile with the depth distribution, and the lateral friction of the supporting pile bears a large part at the loading point, which is caused by the local enhancement effect. However, the frictional resistance distribution of the anti-drawing pile is more uniform, and with the increase of load, (3) the correction coefficient 纬 of positive and negative frictional resistance of pile side in fully weathered granite can be between 0.5-0.6. (4) before the load reaches the limit value, When the load is applied, the pile body near the loading point expands radially under compression, while the pile body drives the soil displacement around the pile and forms a soil arch near the pile end. Under the overburden load, the soil arch effect increases the radial stress of the pile side. The pile side friction increases with it. (5) in the weathered and strongly weathered granite soil layers, it is feasible to use the relevant parameters of sand and gravel to carry out the experimental design.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1
【参考文献】
相关期刊论文 前1条
1 马晔,王陶;超长钻孔桩自平衡法荷载试验研究[J];岩土工程学报;2005年03期
，本文编号：2162924
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