Uncertainty quantification of offshore anchoring systems in spatially variable soil using sparse polynomial chaos expansions

The trend toward deep water energy production has led to a growing use of plate anchors to moor floating production facilities. The effect on anchor uplift behaviour of the inherent spatial variability of soil deposits has so far been little considered, despite having important implications for anchor design. Spatial variability problems are commonly analysed by Monte Carlo simulation but it is difficult to establish the probabilities of failure that are of interest in practice. In this paper, sparse polynomial chaos expansions (SPCEs) are used for moment and reliability analysis of plate anchors in spatially variable undrained clay. A novel two-stage methodology is proposed: in the first stage, an SPCE is constructed to meet a target global error, allowing statistical moments of the uplift capacity to be obtained; in the second stage, an active learning method is used to refine the SPCE for reliability analysis. Anchor uplift capacity is obtained by a finite element method, which is coupled with a random field representation of spatial variability. The effect of embedment depth and the soil-anchor interface is investigated. The failure mechanism of the anchor is shown to have a significant effect on the statistical moments of the uplift capacity and the probability of failure in relation to current design guidelines. To inform future design, factors of safety are presented for a range of failure probabilities.     

向家坝水电站坝基渗控效果研究

为了降低坝基扬压力和减少坝基渗漏量,向家坝工程在坝基设置了防渗帷幕和排水孔幕等渗控措施。基于饱和渗流理论,建立了典型坝段渗流计算模型,采用FLAC3D软件渗流分析模块对坝基渗流场进行了计算,研究了坝基扬压力和排水孔涌水量在不同情况下的变化规律。研究结果表明,向家坝坝基渗控措施排水降压效果明显,可以满足大坝安全稳定的要求。研究成果可对类似工程渗控设计提供参考。     

范厝水电站厂房坝段异常扬压力分析

采用灵敏度现场测试、变化规律定性分析、统计模型定量分析等方法,对范厝水电站大坝厂房坝段坝基防渗帷幕后各测压孔扬压水位异常现象进行了综合分析。分析表明,这些测压孔扬压水位异常,主要是由于进水口部位混凝土内存在与上游水位和测压孔连通的细小裂缝,与上游水位之间不存在明显的关联性,因而不代表厂房坝段坝基防渗帷幕存在缺陷或已被削弱。     

真空激光变形监测系统位移规律异常分析研究

介绍了深溪沟水电站坝顶真空激光变形监测系统位移规律的异常现象,就此进行系统的异常原因分析及测试,并对分析成果进行复核验证。通过对归一系数的改正,有效解决了坝顶真空激光垂直方向和水平方向位移变形规律均呈现"锯齿状"的异常规律,坝段间(或坝块间)相邻测点变形差异和坝顶不均匀上抬现象得到明显改善,可供后续工程参考和借鉴。     

端承桩中的工程桩作抗拔桩的理论分析及实际应用

大颗粒尿素厂房钻孔灌注端承桩基础的施工质量检测中，为了降低工程投资，减少工程成本，利用工程桩作为单桩竖向静荷载试验中的抗拔桩，并对其抗拔承载力进行计算。     

挤扩支盘桩式输电塔基础抗拔承载力计算公式的探讨

文中首先总结目前常用的几种挤扩支盘桩抗拔承载力计算公式,然后结合相关结论、实际工程中获得的实测数据及有限元分析结果,对几种公式进行考察验证,推荐适用于输电塔基础的挤扩支盘桩抗拔承载力的计算公式。     

Displacement and deformation analysis for uplift piles

On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil, that the axis force is distributed as parabola along the pile length, that elastic distortion occurs when the pile is loaded, that the displacement of pile is in accord with that of the soil, and that the uplift pile failure is regarded as the soil failure, a rational calculation method was proposed for calculating the deformation, ultimate displacement and shear resistance of piles. The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method. The comparisons were made between the measurement results and the present results. The present theoretical results agree well with the measurement results, with the average difference being less than 12% before failure. The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles.     

岩石GFRP抗浮锚杆承载性能室内试验与机理分析

基于4根岩石GFRP抗浮锚杆的室内足尺拉拔破坏性试验,探讨了风化岩地基中全长黏结GFRP抗浮锚杆的界面黏结特性和承载性能,揭示了GFRP锚杆的细观破坏机理。结果表明：GFRP抗浮锚杆发生拔出破坏,主要是由螺纹表面劣化所引起的剪胀破坏;直径25 mm、灌浆体强度M30、锚固长度1.3和0.55 m的GFRP抗浮锚杆的极限抗拔承载力分别为255、195 kN,满足工程抗浮要求;GFRP抗浮锚杆杆体与灌浆体界面平均黏结强度介于2.41~5.10 MPa之间,高于《岩土锚固与喷射混凝土支护工程技术规范》（GB 50086—2015）中钢锚杆与灌浆体的黏结强度推荐值。     

索连板球基础上拔机理

针对既抗压又抗拔基础存在的缺陷和不足,尤其是特殊场地条件下施工困难的问题,构建了索连板球基础。该基础主要由水泥土柱、上板、下球体和须发锚索4部分构成,其中水泥土柱、下球体与须发锚索构成球索基础,由该球索基础承担上拔力。通过理论推导和数值模拟,分析了球索基础的抗拔机理及其与土体之间的相互作用,以及球索基础周围土体的变形开裂过程,揭示了球索基础的变形破坏规律和上拔力与埋深比之间的关系。     

不同组合下高喷插芯组合桩抗拔承载特性试验研究

基于自主研发的大型桩基模型试验加载系统,采用砂雨法施工,对4种不同组合形式的高喷插芯组合桩（JPP桩）进行了抗拔承载性能对比试验研究。结果表明：1）JPP桩的不同组合形式对抗拔承载力有较大影响,下组合抗拔承载能力最高,其承载能力是分段组合II的1.1倍,是分段组合I的1.3倍,是上组合的1.4倍。2）极限荷载下,组合段所提供的总侧摩阻力中,下组合最高。3）在桩体上拔过程中,桩身轴力沿桩身向下依次递减;随着荷载的增加,桩身上部侧摩阻力首先达到极限值并趋于稳定,然后桩身中下部侧摩阻力逐渐发挥。4）侧摩阻力随桩土相对位移的增加而逐渐变大,在桩土相对位移较小时便达到较大值,桩身上部的侧摩阻力在达到较大值后趋于稳定,桩身中下部不同位置处的侧摩阻力在达到较大值仍有不同程度递增的趋势,总体上呈现出双曲线的分布形式。