新铁高速公路软土地基碎石桩加固处理

本文通过对新铁高速公路软土区的地质情况和特点的分析,确定采用碎石挤密桩来加固软土地基。由碎石桩设计、施工过程、工艺控制、质量检查等进行详细的阐述;施工后通过对桩基、装间土和复合地基承载力的检测试验,证明该处高速公路碎石桩能够满足地基处理的要求。     

长短桩复合地基的设计与应用

依托杭州某高速公路工程实践,介绍了长短桩复合地基的作用机理、设计及在实际工程中的应用。     

浅谈NCS土壤固化剂在无砂石地区的应用

以我省无砂石地区双城市为例,介绍了ＮＣＳ土壤固化剂的使用及其效果。     

载荷试验确定粉喷桩复合地基承载力的探讨

静载试验是目前确定复合地基承载力较为可靠的原位测试技术之一。文章结合某路基软土处理工程实例,分析了由载荷试验确定复合地基承载力的几种常用方法,提出采用相对沉降法来确定粉喷桩复合地基承载力,同时采用双曲线拟合法或回弹法来检验其方法的可靠性,以保证水泥粉喷桩处理软土地基的加固效果。     

Axisymmetric structural behaviours of composite tensile armoured flexible pipes

To address the weight and corrosion challenge in deep-water, replacing the steel tensile armour in flexible pipes with composite materials is an alternative conceptual approach. An axisymmetric structural responses model is built for this novel composite armoured flexible pipe, with interlayer gaps that may occur in the unbonded structure considered through an iterative algorithm. The tensile strength of steel and composite armoured pipes are predicted based on different constitutive relations of steel and composite. Essential quantities are obtained, such as tensile stiffness, deformations of each layer and interlayer gaps or contact pressures. Considering the helix form of carcass and pressure armour, a finite element model is established for the verification of the theoretical model. Case study shows that the tensile stiffness of flexible pipe is overestimated with the interlayer gap ignored. Compared with steel armoured flexible pipe, the composite armoured pipe, whose tensile stiffness decreases less as external pressure increases, meanwhile has higher values of tensile ultimate strength and torsion stiffness. Some suggestions about fiber types and volume fraction for composite tensile strips are given to ensure good performance of axial tensile strength and stiffness.     

复合轨枕无砟轨道温度适应性分析

为研究温度荷载对复合轨枕无砟轨道影响,分别建立长枕埋入式和双块式复合轨枕无砟轨道有限元模型,分析两种轨道结构在整体降温和温度梯度下的离缝长度和轨距变化量,并给出降温限值。结果表明:在整体降温条件下,两种轨道结构均产生离缝,双块式轨道的轨距变化量随降温幅度变化较小,综合考虑离缝和轨距变化限值影响,长枕埋入式、双块式轨道降温幅度分别不应超过7,11℃;温度梯度下,两种轨道结构均不产生离缝,仅正温度梯度下长枕埋入式轨距变化量超过规范值。从复合轨枕轨道结构对温度适用性考虑,建议在较小温差地区如隧道内铺设双块式轨道,并注意浇筑时混凝土的温度。     

Hydrothermally degraded carbon fiber / epoxy plates subjected to underwater explosive loading in a fully submerged environment

An experimental and computational investigation was conducted to evaluate the underwater blast response of fully submerged carbon fiber composite plates after prolonged exposure to saline water. The material was a biaxial carbon fiber/epoxy composite with a [±45°] fiber orientation layup. The plates were placed in a saline water bath with a temperature of 65 °C for 35 and 70 days, which simulates approximately 10 and 20 years of operating conditions in accordance to Fick's law of diffusion coupled with Arrhenius's Equation and a reference ocean temperature of 17 °C. Underwater blast experiments were performed in a 2.1 m diameter pressure vessel. The composite plates were placed in the center of the vessel while fully submerged in water, and an RP-85 explosive was detonated at a standoff distance of 102 mm from the center of the plate. Two cases of fluid hydrostatic gage pressures were investigated: 0 MPa, and 3.45 MPa. Two high speed cameras were utilized for three-dimensional Digital Image Correlation, which provided full-field displacements and velocities of the composite plates during underwater blast loading. A third high speed camera captured the behavior of the explosive gas bubble. Moreover, the pressure fields generated by the explosive detonation and resulting gas bubble were recorded with tourmaline pressure transducers. A water diffusion study was completed which showed that the diffusion of water into the composites reached a point of complete saturation after 35 days of exposure. Quasi-static material characterization tests were performed before and after prolonged exposure to saline water. The properties obtained from quasi-static testing also served as material inputs for the numerical models. The quasi-static test results showed that the tensile modulus E_1,2 does not change with exposure to saline water, whereas the in-plane shear modulus G₁₂ decreases with saline water exposure. During blast loading, for the case of 0 MPa hydrostatic gage pressure, the gas bubble interacts with the composite plate substantially. In such an event, the out of plane displacement increased for saline water exposed plates when compared to virgin structures. For the case of 3.45 MPa hydrostatic gage pressure, the gas bubble does not visibly interact with the composite plate. In this case, the out of plane displacement for specimens exposed to saline water was similar to the virgin specimen. A fully coupled Eulerian–Lagrangian fluid structure interaction simulation was performed by using the DYSMAS code. The numerical simulations showed that the displacement of fully submerged composite plates is driven by the displacement of fluid, as well as the size of the gas bubble formed by the explosive rather than the peak pressure generated by the explosive. The numerical simulations were in agreement with the experimental findings in terms of pressure history and plate deformation.     

The wet-towing resistance of the composite bucket foundation for offshore wind turbines

The composite bucket foundation (CBF) is a new and environmentally-friendly foundation for offshore wind turbines. This foundation can be prefabricated in batches onshore followed by integrated transport and installation at sea. The structure itself has a subdivision air cushion structure that enables the foundation to float stably on the water surface and realize long-distance towing of the foundation. The mechanism of this air-liquid-solid coupling towing process is complicated, and the influence of the bulkheads on the towing resistance is not clear. In this paper, the influence of the subdivision structure on the towing resistance of the CBF is compared with the tow test in hydrostatic water. The structural motion characteristics and the change of the cushion pressure are also analysed. Experiments are used to verify numerical calculation results. The flow field difference between the CBF with bulkheads, the CBF without bulkheads and the real floating structure was analysed. The dynamic pressure coefficient was used to analyze the force at surfaces of different CBF's. For the tow test and numerical calculation of multiple CBFs, the optimal multi-CBF tow distance and towage number are obtained through the calculation of energy consumption rate.     

我国综合交通系统的社会贡献评价研究——以2000-2017年数据为例

本文首先介绍了研究背景,提出研究目的。通过梳理国内外相关文献,提出现有研究尚未涉及综合交通系统社会贡献方面。在解析综合交通社会贡献机理基础上,根据我国2000—2017年社会系统和综合交通数据确定我国社会系统发展指数S和交通系统发展指数T的组成指标,在每种交通方式内采用因子分析法确定各指标权重,结合各指标数值得到S和T数值。应用格兰杰检验法证明T是S的原因,由S关于T的回归函数可得我国综合交通社会贡献评价函数,处理后得到最佳状态数值,发现实际数值与之相比仍有较大提升空间。最后,提出相关政策建议。     

Structural analysis of an offshore vertical axis wind turbine composite blade experiencing an extreme wind load

The vertical axis wind turbine (VAWT) configuration has many advantages for an offshore wind turbine installation. The VAWT is omnidirectional and its rotating mechanical components can be placed close to sea level. In this paper, the structural analysis of a VAWT blade structure subject to a critical load case was investigated with two methods, an analytical model and a finite element (FE) model. It was shown that the utilisation of a composite blade topology can resist the induced flapwise loading and the material strains were contained within their allowable limits. The analytical approach was demonstrated to be a quick and accurate technique to compute the composite blade strain distribution when compared to the FE model results.