隧道工程中钢-混复合衬砌力学承载能力试验研究

依托于南北通道建设工程区段隧道匝道建设工程,对施工工程中的钢-混复合结构进行力学承载能力试验。试验结果表明:“栓钉”结构的混凝土在加载至2 800 kN时,出现裂缝,加载力达到4 000 k N时,会出现完全破碎;“肋板+栓钉”结构的混凝土在加载至3 000~3 200 kN时,出现裂缝,加载力达到4 300~4 500 kN时,会出现完全破碎。“肋板+栓钉”结构的混凝土中肋板的存在可以阻止腹板的变形,减缓了内部工字钢和混凝土的错动发展,但从承载力数据来看,效果并不明显。通过光纤监测,可以进一步佐证裂缝产生的时间,且在裂缝位置监测的准确度上可以达90%以上。

RC梁承载力试验及数值分析研究

【目的】通过对RC梁进行四点受弯分级加载试验,研究受弯破坏对RC梁承载力的影响规律,并基于有限元分析软件建立数值模型以验证试验结果。同时,运用规范公式计算与上述值进行比较分析。【方法】通过包括试验测试、数值模拟和规范公式计算等三种方法研究RC梁的承载能力。【结果】研究结果表明,所建立的模型能够较好地预测RC梁的承载力,这为准确评估RC梁的安全性能提供了有力支撑。【结论】钢筋混凝土梁在弯曲破坏形态下的破坏试验法虽然真实准确,但不宜在实际工程中应用,而有限元分析法可以高精度、快速、低成本地模拟全过程,且与试验吻合较好。规范计算则偏于理想化,因此需要根据具体对象选取适当的方法。

软岩巷道围岩卸荷破坏力学模型及影响因素分析

为了研究深部软岩巷道开挖卸荷作用下的力学响应量及大变形失稳机理,基于统一强度准则和岩石三线段力学模型,建立了巷道围岩开挖卸荷力学模型,依据巷道开挖后围岩次生切向应力、等效剪应力分布特征,将围岩力学结构划分为浅承载圈、深承载圈、自稳承载圈、主承载圈和关键承载圈,通过理论分析,求解得到软岩巷道开挖后次生应力场、位移场以及软化区与破碎区范围解析解,结合某软岩工程相关力学参数,分析了巷道开挖卸压作用下围岩屈服应力,围岩破裂区、软化区影响范围以及围岩承载结构的影响因素。研究表明:围岩屈服应力随着初始黏聚力和内摩擦角的减小以及掘进速度的增大而减小,围岩越容易达到屈服发生破坏;围岩软化区范围与围岩初始力学参数相关,初始黏聚力越大的围岩,围岩软化区范围减小;破碎区范围随着黏聚力软化模量、剪胀角、掘进速度以及支护结构间排距等的增加而增大;主承载圈和关键承载圈的范围、径向应力和轴向应力的峰值随着围岩软化程度的增加而增大,且向巷道深部转移。

沉管干振挤密碎石桩的承载力分析

基于工程实践,采用规范推荐的公式和基于Brauns理论的改进公式计算复合地基承载力,同时,与现场大型静载试验得到的碎石桩复合地基承载力进行了对比分析。研究表明,按此2个公式计算复合地基承载力时,误差较小,均可用于实际工程。按基于Brauns理论的改进公式计算时,计算结果稍大。

用统一强度理论求岩基极限承载力

基于统一强度理论,将岩基承载力问题视为空间问题,考虑了中间主应力的影响,推导出了岩基承载力的计算公式。当中间主剪应力的影响系数b=0时,其计算公式与采用Mohr-Coulomb强度理论所求得的解完全相同。并讨论了b对承载压力的影响,分析表明:岩基承载力随着b值的变化而不同,从而说明所推导公式对岩基承载力计算有一定的指导意义。

工程车辆翻新轮胎接地力学特性分析

为进一步明确翻新轮胎的力学性能并提高其使用寿命,构建工程车辆翻新轮胎静态接地工况三维模型、轮胎与地面接触模型、静态接地工况有限元分析模型及承载-接地力学特性试验系统。分析结果表明:静态接地工况、接地压力及接地摩擦力在轮胎与地面接触区域内中心位置达到最小值,沿轮胎滚动方向及宽度方向呈现不同程度增大的"V"型分布规律;当载荷较小时,接地印痕形状近似为圆形,随着载荷不同程度地增大,其形状变化由近似圆形到近似椭圆形,再到近似矩形,最后到近似马鞍形的变化规律;当胎压一定时,随着载荷的增加,接地面积逐渐增大,增大趋势呈现非线性变化规律;工程翻新轮胎胎肩部位接地压力及接地摩擦力均最大,该部位较容易发生橡胶崩花掉块、撕裂脱层的失效损坏现象。

钢管混凝土核心短柱轴压承载力影响参数分析

基于假定的合理的钢管混凝土核心短柱各部分材料本构模型,依据力的平衡和变形协调两个条件,建立了组合柱轴压承载力分析力学模型;据此分析了位置系数、钢管含钢率、配箍特征值及混凝土强度等参数对其柱轴压承载力提高百分率的影响,并建议了较为经济的组合柱参数范围,其结论可为工程应用提供依据。

旧水泥浇混凝土路面沥青加铺层结构力学解析

早在1854年的巴黎有了接近现在技术的薄层沥青路面,通过0. 074 mm的粉粒达到40%以上,引领了当时路面结构的主流。而随着使用时间的不断延长和其他人为、社会等因素的影响下,沥青路面便无法满足正常行车的条件,需要及时的修补。因此,大体从交通因素,和温度因素的角度去分析考量沥青加铺层结构力学性能的影响规律,旨在改善旧水泥浇混凝土路面的接缝传荷能力,从而强化其内部的应力应变状态。

基于经验的桩基承载力灰色系统分析与评价

桩基承载力是一个受多因素影响、随时空变异的动态系统,它具有数据有限、不确定等特点,因此,已有的成功经验知识的运用在桩基承载力评价中具有重要的意义。基于灰色系统理论,提出了一种定量开发利用经验知识的方法,并将其成功地应用于桩基承载力的分析与评价。结果表明,在运用经验知识方面,该法与目前广泛使用的神经网络方法有异曲同工之妙。此外,所提出的方法还具有简单、方便和实用等许多优点。

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.

激素性股骨头坏死囊性变分布规律及病理特点

背景:股骨头力学承载能力下降是引起股骨头塌陷的主要原因,而囊性变的产生影响了髋关节正常的力学传导途径,但目前很少有文献对股骨头坏死发展过程中二者的关系进行探索。目的:结合热力图模型和激素性股骨头坏死病理结果探讨激素性股骨头坏死囊性变的分布规律及病理特点。方法:以2021年6-12月于广州中医药大学第三附属医院被诊断为激素性股骨头坏死的30例(30髋)患者为研究对象,提取激素性股骨头坏死囊性变轮廓线,将轮廓线匹配至标准股骨头模型上,对轮廓线进行热图呈现;统计股骨头坏死位置与坏死面积,研究二者之间的关系;苏木精-伊红染色观察股骨头标本骨组织形态结构变化。结果与结论:①通过构建激素性股骨头坏死囊性变热力图及结合股骨头病理结果发现,激素性股骨头坏死囊性变好发于股骨头中外侧柱,相较于内侧柱囊性变的面积而言,外侧柱囊性变面积最大,且随着囊性变发生位置的内移,其面积也会随着减小;②并且囊性变周围散在分布微小骨折线,它可能是影响股骨头力学承载能力和头内稳定性的重要因素之一。

Mechanical performance of the mixed post-installed connection in low-strength concrete

Due to inadequate bearing capacity of the chemically-planted steel bar in low-strength concrete, a new mixed post-installed connection is proposed using small diameter anchoring steel bars and grouting materials together to anchor the main steel bar. To investigate the feasibility of the proposed post-installed connections, a series of pull-out tests with different anchors were conducted for comparison,including fully adhesive anchors, partially adhesive anchors,grouting material anchoring connection and the new mixed post-installed connection. The experimental results of the single steel bar pull-out test show that the mixed post-installed connection can effectively enhance the bearing capacity of post-installed steel bars in low-strength concrete. The bearing capacity is increased by nearly two times with no cone-type concrete failure compared with the fully adhesive anchor. The results show that adopting the new mixed post-installed connection can ensure that joint performance meets the requirements if the space dimension is available.

有关上部结构-桩-土相互作用研究问题探讨

对桩-土相互作用研究成果进行了综述,重点讨论了桩-土相互作用研究进展、承载力以及沉降计算等方面的内容,并提出了今后研究的一些发展方向。

Mechanical Behavior of Rectangular Steel-Reinforced ECC/Concrete Composite Column under Eccentric Compression

In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.

Mechanical property of single-bolted composite laminates

In order to investigate the effects of different geometrical parameters and pretightening loads on failure mode and bearing strength,a large number of single-bolted T300/QY8911 composite laminates were tested under static tension load.Box-plot was used to extract the singular testing values of bearing strength and effective statistical values were obtained.T-test method of independent samples was used to study how much pretightening loads influence bearing strength.The results show that the geometrical parameters,such as ratios of width to hole diameter(w/d) and edge distance to hole diameter(e/d),remarkably influence failure mode and bearing strength.Net-section failure will occur when w/d is smaller than 4,and shear-out failure will occur when e/d is smaller than 2.Bearing failure or bearing and shear-out combined failure will occur when w/d is greater than 4 and e/d is greater than 2.There is an optimal combination of geometrical parameters to achieve the highest bearing strength.For most of specimens,pretightening loads do not explicitly influence bearing strength.

Mechanical characteristics of columnar jointed rock at dam base of Baihetan hydropower station

Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineering, hydraulic and hydropower engineering caused by columnar jointed basaltic mass, Voronoi graph from geometry was introduced to simulate the irregular columnar jointed basaltic mass at Baihetan hydraulic station. Discrete element software UDEC was used to simulate the whole process of rigid bearing plate test. Anisotropic constitutive of columnar joints was adopted to analyze the stress diffusion of rock mass at dam base of Baihetan. The results show that, the compaction property and hysteresis effect are well simulated based on discrete element simulation of Voronoi joint structure by UDEC. Four stages of cyclic loading and unloading process are imaged clearly. The results from in situ rigid bearing plate tests are explicated and the stress diffusion rule of anisotropic body is affected by structure surface. The elements in the stress state of 4-5 MPa are the most, about more than 35% of the total. Appropriate constitutive must be proposed to columnar jointed rock mass with different styles. It has important significance to realize the nonlinear mechanical behavior of irregular columnar jointed basaltic mass.

Comprehensive Measurement for Carrying Capacity of Resources and Environment of City Clusters in Central China

Studying the carrying capacity of resources and environment of city clusters in the central China has important practical guidance significance for promoting the healthy, sustainable and stable development of this region. According to their influencing factors and reciprocity mechanism, using system dynamics approaches, this paper built a SD model for measuring the carrying capacity of resources and environment of the city clusters in the central China, and through setting different development models, the comprehensive measurement analysis on the carrying capacity was carried out. The results show that the model of promoting socio-economic development under the protection of resources and environment is the optimal model for promoting the harmony development of resources, environment, society and economy in the city clusters. According to this model, the optimum population scale of the city clusters in 2020 is 42.80×106 persons, and the moderate economic development scale is 22.055×1012 yuan (RMB). In 1996-2020, the carrying capacity of resources and environment in the city clusters took on obvious phase-change characteristics. During the studied period, it is basically at the initial development stage, and will come through the development process from slow development to speedup development.

Research on the Knowledge System Framework of Eco-industrial Engineering

With intensified contradiction between the rapid devel- opment of modem industry and the carrying capacity of natural environment, coordinating the relationship between economic benefits and ecological benefits is a significant issue to be solved for modem industrial engineering. This paper firstly conducts the comparative analysis between traditional and ecological industry as well as traditional and modem industrial engineering, and in- dicates that eco-industrial engineering is an inevitable choice for sustainable development of modem industrial engineering; Then, based on industrial ecology, environmental economics and sustain- able development theory, the connotation and definition of eco- industrial engineering are proposed, and the theoretical and practi- cal development of the concepts of eco-industrial engineering are further investigated. Furthermore, the research subject, research content, academic system architecture and evaluation methods of eco-industrial engineering are discussed. Finally, combining the current scientific and technological development, we put forward the important scientific value and practical significance of con- structing eco-industrial engineering for the utilization of these concepts.

风电转盘轴承设计参数对承载能力的影响

针对风电转盘轴承的结构特点，根据轴承受载产生内、外圈相对位移后的几何关系，得出钢球一沟道之间的弹性趋近量表达式，以套圈相对位移为未知变量建立了轴承的平衡方程组，并结合某具体型号的轴承，研究了轴承的游隙、沟曲率半径系数、接触角等参数的改变对轴承承载能力的影响，结果表明：适量小的负游隙可使轴承具有极佳的承载性能；减小沟曲率半径系数可提高其承载能力；轴承的轴向载荷相对数值较大时，增大接触角可以提高其承载能力。

跨域翼身融合变体飞行器结构/机构一体化设计

将变体设计与翼身融合飞行器结合,是提升其飞行性能、实现跨域飞行的有效途径。如何协调飞行器结构变形、力学承载和轻量化的关系至关重要。首先分析了翼身融合飞行器在典型变形状态下的气动特性,指出兼顾展向和弦向的机翼构型变化可有效扩展飞行包线、调整静稳定度,并给出典型飞行阶段中飞行器变形状态。其次为实现飞行器双向组合变形,提出了分布式异构连杆机构设计方案。再次为解决飞行器变形和承载之间的矛盾,根据各变形状态下气动载荷特点,提出了分布式变拓扑承载梁设计方案,实现兼顾轻量化的飞行器变形/承载一体化设计。最后在仿真分析的基础上,完成变形驱动方案样件加工,并对其变形能力进行试验验证。结果表明,跨域翼身融合变体飞行器可改变其形状以适应多种载荷条件,实现大空域、宽速域的敏捷飞行。