砂土中静压管桩桩周土压力及承载特性的模型试验研究

发布时间：2018-11-26 19:50

【摘要】：静压桩具有施工速度快,无污染、噪音低、无振动、无冲击力等许多优点,因此用途比较广泛,尤其是在软土等地基中。静压桩属于挤土桩,在贯入过程中受到土体挤压,单桩产生桩-土相互作用,从而周围土体的密实度发生变化,进而桩周土压力会相应的改变;沉桩完成后随着时间的增加,由于土体的自稳和重塑,承载力会相应的提高。因此,能有效预估静压桩产生的挤土效应、探究它的周围土体应力变化以及自身的承载特性,对工程具有很大意义。本文首先对静压桩的沉桩受力特性和承载力特性结合国内外研究现状进行了总结,本文着重对如下内容进行了研究:(1)对两种桩身承载力理论计算进行了详细的推导,包括基于球孔扩张理论桩端承载力的比较和经典的桩基础地基承载力公式进行了说明。推导出静压桩贯入土体过程中桩身法向应力、径向应力、和塑性区位移的一般解;给出了塑性区的平均体积应的一般解;在沉桩终压力的基础上给出了桩端承载力的公式,应用此公式可对桩端承载力进行预测,并介绍了两种桩基础承载力的经典公式。(2)为探究桩土相互作用的大小,需要测得桩土界面的土压力,为此提出了三种测土压力的方法:薄膜压力传感器、土压力盒、悬臂式土压力测量装置,对于三种测量方法进行了室内标定试验。悬臂式土压力测量装置可以减小土拱效应,在模型桩试验中,土压力盒的优点比较突出,薄膜压力传感器有待于进一步研究。(3)基于原有的静压桩竖向加载系统,改进了设备,通过滑板代替原有的滑杆提高压桩过程中压桩系统的刚度,使模型桩贯入过程中的垂直精度进一步提高。采用PLC伺服电动缸控制,实现自动、稳定和精确加载。自主研发了一种多功能模型试验桩,该模型桩通过内嵌土压力盒及其桩端设置力传感器,能够精确测量出桩土界面的土压力大小及其桩端阻力的大小。(4)在模型箱中进行静压桩贯入过程及静载的试验,探究在不同沉桩速度完成后,测得的各个桩深处的土压力大小,以及贯入过程中桩侧摩阻力、桩端阻力、压桩力以及桩端残余应力的变化规律。通过静载试验探究单一砂土中静压单桩的承载特性及规律。对本文试验得到的结果与承载力理论计算方法进行了比较,探究它们之间的相互关系与区别。
[Abstract]:Static pressure pile has many advantages, such as fast construction speed, no pollution, low noise, no vibration, no impact force and so on, so it is widely used, especially in soft soil foundation. Static pressure pile is a kind of compaction pile, which is squeezed by soil in the process of penetration, the pile-soil interaction is produced by single pile, so the compactness of surrounding soil changes, and the soil pressure around pile will change accordingly. With the increase of time, the bearing capacity of the pile will be increased due to the self-stability and remolding of the soil. Therefore, it is of great significance for engineering to estimate the squeezing effect of static pressure pile effectively, to explore the stress change of soil around it and its bearing characteristics. In this paper, the mechanical characteristics and bearing capacity characteristics of static pressure pile are summarized firstly. The main contents of this paper are as follows: (1) the theoretical calculation of bearing capacity of two kinds of piles is deduced in detail. The comparison of pile end bearing capacity based on spherical hole expansion theory and the classical formula of pile foundation bearing capacity are presented. The general solutions of normal stress, radial stress and plastic region displacement of the pile body during the penetration of static pressure pile into soil are derived, and the general solution of the average volume response of plastic zone is given. Based on the ultimate pressure of pile-sinking, the formula of pile-end bearing capacity is given, which can be used to predict the pile-end bearing capacity, and two classical formulas of pile-foundation bearing capacity are introduced. (2) in order to explore the magnitude of pile-soil interaction, It is necessary to measure the earth pressure at the pile-soil interface. For this reason, three methods of measuring the earth pressure are put forward: the thin film pressure sensor, the earth pressure box and the cantilever earth pressure measuring device, and the indoor calibration tests are carried out for the three measuring methods. The cantilever earth pressure measuring device can reduce the soil arch effect. In the model pile test, the advantages of the earth pressure box are outstanding, and the membrane pressure sensor needs further study. (3) based on the original vertical loading system of static pressure pile, The equipment is improved, and the stiffness of the pile-pressing system is improved by replacing the original slider with the slide plate, so that the vertical precision of the model pile in the process of penetration is further improved. PLC servo electric cylinder control is used to realize automatic, stable and accurate loading. A multi-function model test pile is developed. The model pile is set up through the pressure box and the end of the pile. It can accurately measure the soil pressure at the pile-soil interface and the resistance at the end of the pile. (4) the static pressure pile penetration process and static load test are carried out in the model box. The soil pressure of each pile is measured, and the variation law of pile side friction, pile tip resistance, pile-pressing force and residual stress in the process of penetration is obtained. The bearing characteristics and law of static pressure single pile in single sand are studied by static load test. The results obtained in this paper are compared with the theoretical calculation method of bearing capacity, and the relationship and difference between them are explored.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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