黏土充气锚杆承载特性及群锚效应试验研究

发布时间：2018-06-10 15:30

本文选题：充气锚杆 + 黏土地基　；参考：《湖南科技大学》2017年硕士论文

【摘要】：我国沿海广泛分布着软弱地基区,充气锚杆具有较强的承载性能、可立即提供锚固力、可回收利用等优点,在海洋工程及软弱地基区有着广阔的应用前景。国内外许多学者对充气锚杆进行了研究,但充气锚杆在黏土地层中的研究尚未涉及,其承载特性及锚固机理尚不明确。因此,作为一种新型锚杆,有必要在尚未应用过的地层和环境下对其进行研究。本文基于前人的研究基础,采用室内模型试验的方法,对充气锚杆在黏土地层中不同试验因素条件下的承载特性与群锚效应等方面进行了探索性研究,主要研究内容与成果如下:(1)根据试验需求,在广泛调研的基础上研制了充气锚杆模型和用于单锚、群锚抗拔试验的整套模型试验装置。(2)开展充气锚杆扩大段变形特性研究,获得不同压力下充气锚杆端头扩大段膨胀体积与等效直径的变化规律;开展了不同埋深、充气压力、填土含水率条件下的抗拔试验研究表明:埋深增大,极限承载力随之增长。由于端头扩大段的影响,使得极限承载力得到了较大的提高,其承载力占比为45%~51.8%;充气压力为影响极限承载力的最大因素,在一定气压范围内,增加充气压力能有效地提高充气锚杆的锚固性能;充气锚杆在含水率接近液限的黏土地层时仍具有较高的承载力。基于非线性最小二乘法原理对获得的试验数据进行拟合得出充气锚杆Q-S曲线服从幂函数分布规律。(3)充气锚杆在黏土中Q-S曲线可分为弹性阶段、弹塑性阶段和塑性阶段;通过分析加载-卸载试验获得的Q-S_E,Q-S_P关系曲线,其分界荷载分别为23.5%_、83.5%Q_u。(4)开展了循环荷载试验,探讨了充气锚杆在循环荷载条件下承载及位移演化规律,得出在一定范围内存在一最小循环荷载次数,当循环荷载次数小于该值时,累积沉降位移随着循环次数的递增而增加,反之,累积沉降位移收敛,在接近极限荷载条件下循环荷载累积位移不收敛。(5)开展了群锚抗拔试验,双锚随着锚杆间距的增大承载能力先减弱后增强,获得了峰值点间距为_=6.84D。三锚、四锚在间距Ru条件下的对比抗拔试验表明四锚(矩形)布置形式从承载性能及位移控制均要优于三锚(三角形)布置形式。(6)基于极限平衡分析法原理,建立了充气锚杆承载力计算模型。根据典型黏土抗拔结构与充气锚杆抗拔特点进行类比分析,引入浅埋充气锚杆在黏土中喇叭形破裂面的计算方程,并运用数值分析软件,推导出充气锚杆极限承载力Qu的估算公式。
[Abstract]:The soft foundation area is widely distributed along the coast of our country. The aerated anchor rod has strong bearing capacity, can provide anchoring force immediately, can be recycled and so on. It has a broad application prospect in marine engineering and soft foundation area. Many scholars at home and abroad have studied the aerated anchor rod, but the research of the aerated anchor rod in clay stratum has not been involved, and its bearing characteristics and anchoring mechanism are not clear. Therefore, as a new type of anchor, it is necessary to study it in the unapplied strata and environment. Based on the previous research, this paper makes an exploratory study on the bearing characteristics and group anchor effect of aerated anchor rods under different experimental factors in clay strata by using the method of indoor model test. The main research contents and results are as follows: (1) based on the extensive investigation and research, the inflatable anchor model and the complete set of model test equipment for single anchor, group anchor pull-out test are developed to study the deformation characteristics of the expanded section of the aerated anchor. The expansion volume and equivalent diameter of the expanded end of the aerated anchor are obtained under different pressures, and the pull-out tests under the conditions of different burying depth, inflatable pressure and water content of the fill show that the ultimate bearing capacity increases with the increase of the buried depth. Due to the influence of the end expansion section, the ultimate bearing capacity has been greatly improved, and the proportion of the ultimate bearing capacity is 451.8.The inflatable pressure is the biggest factor affecting the ultimate bearing capacity, and within a certain pressure range, The Anchorage performance of the aerated anchor rod can be improved effectively by increasing the inflatable pressure and the bearing capacity of the aerated anchor rod is still high when the water content is close to the liquid limit. Based on the principle of nonlinear least square method, the Q-S curve of inflatable anchor can be divided into three stages: elastic stage, elastic-plastic stage and plastic stage, according to the distribution law of power function. The Q-S curve can be divided into three stages: elastic stage, elastic-plastic stage and plastic stage. By analyzing the Q-SSP relation curve obtained from the load-unloading test, the dividing load of Q-SSP is 23.53.5Qu.Qu.f. respectively) the cyclic load test is carried out, and the law of bearing capacity and displacement evolution of inflatable anchor rod under cyclic load is discussed. It is concluded that there is a minimum number of cyclic loads in a certain range. When the number of cyclic loads is less than this value, the cumulative settlement displacement increases with the increase of cycle times, whereas the cumulative settlement displacement converges. Under the condition of close to the limit load, the cumulative displacement of cyclic load is not convergent. The pull-out test of group anchors is carried out. With the increase of anchor spacing, the bearing capacity of double anchors decreases first and then increases, and the peak-point spacing is 6.84D. The comparative pull-out test of three anchors and four anchors under the condition of spacing Ru shows that the layout of four anchors (rectangular) is superior to that of three anchors (triangle) in loading performance and displacement control based on the principle of limit equilibrium analysis. The calculation model of bearing capacity of aerated anchor rod is established. According to the characteristics of typical clay anti-drawing structure and inflatable anchor rod, this paper introduces the calculation equation of shallow buried aerated anchor rod in clay, and applies the numerical analysis software to calculate the fracturing surface of shallow aerated anchor rod in clay. The formula for estimating the ultimate bearing capacity of aerated anchor rod is derived.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU476

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