风化料的强度与变形特性及其影响因素分析

按照相似级配法将风化料的粒径缩小后,进行物理力学性质试验研究,并采用干湿循环模拟风化料的进一步风化进行试验.基于此,探讨了风化料的强度特性和变形特性,对风化料快速法与常速法压缩试验的结果进行了比较,分析了影响凤化料强度和变形特性的各种因素.     

废旧轮胎颗粒-砂混合物的水平循环剪切特性试验研究

对废旧轮胎颗粒-砂混合物进行水平循环剪切试验,研究竖向荷载、轮胎颗粒含量以及轮胎颗粒尺寸3种因素对混合物的等效动剪切模量和等效阻尼比的影响.结果表明:竖向荷载越大,轮胎颗粒与砂混合物的动弹模量越大,等效阻尼比越小;轮胎颗粒含量增加,混合物的等效动剪切模量与等效阻尼比并不是都呈单调变化;试验中,在相同条件下,小粒径的轮胎颗粒与砂混合物的动弹模量相对要小,等效阻尼比要大一些.上述的试验结果给废旧轮胎颗粒-砂混合物在工程应用提供一定的参考.     

砂土介质中废旧轮胎加筋条带拉拔特性

为减少废旧轮胎大量堆放对环境造成的严重污染及潜在安全隐患,基于废旧轮胎良好的抗拉伸、耐老化及界面粗糙等特性,本研究提出将废旧轮胎切割成条,制成加筋条带,用作土工加筋材料的新型利用方法。通过调整砂土不同密实度条件,对比开展废旧轮胎条带及土工格栅拉拔特性试验研究。结果表明,砂土介质中废旧轮胎条带达到极限拉拔力之前,拉拔位移随拉拔力的增长而线性增长;极限拉拔力统计表明,加筋条带界面抗剪强度符合摩尔-库仑强度准则,并由此建立界面抗剪强度与界面摩擦角及似黏聚力的线性关系。通过对比土工格栅加筋性能,发现废旧轮胎条带的剪应力峰值约为土工格栅的2.5~3.2倍;达到剪应力峰值所需要的位移约为土工格栅的5倍。研究成果验证了废旧轮胎条带作为加筋材料的可行性,为进一步开展理论研究及工程应用奠定了基础。     

矿物掺和料-水泥浆体电学特性与其微结构的关系

采用循环伏安法和交流阻抗法系统研究了粉煤灰、矿渣粉和石灰石粉水泥浆体的电学特性,通过等效电路对电学测试结果进行拟合,并将拟合所得浆体电学参数与浆体化学结合水和压汞所测孔结构之间的相关性进行比较。结果表明：浆体的化学结合水与其电阻率具有较好的正相关性,即化学结合水越多,水化程度越大,浆体电阻率越高;粉煤灰和矿渣粉可以提高浆体电阻率,而石灰石粉在5%掺量下对浆体电阻率无影响;随着水化龄期的延长,浆体孔溶液电阻增大,其变化规律与浆体电阻率一致;浆体凝胶电容和凝胶电阻与C-S-H凝胶含量有关,二者有很好的负相关性;随着水化龄期的延长,浆体孔结构曲折程度提高,交流阻抗法所测得常相角指数减小,压汞测得的分形维数增大。     

可溶盐作用下水泥稳定花岗岩风化料特性

为了分析水泥稳定花岗岩风化料底基层的病害机理,并优化材料设计,通过3种不同粗集料含量的水泥稳定花岗岩风化料不同养生条件下的材料性能试验,分析了粗集料含量(质量分数)对风化料抗可溶盐腐蚀性能的影响。研究结果表明:长期的水环境,尤其是存在可溶盐腐蚀介质的水环境会导致水泥稳定花岗岩风化料性能的迅速衰减;粗集料含量小于20%时,在可溶盐腐蚀介质的作用下,材料的物理力学性能极差,随着粗集料含量的增加,除标准养生条件下材料的劈裂强度略有降低外,各种条件下的材料性能均得到明显改善;粗集料含量由20%增加到30%,对于改善各种环境下材料的抗压性能和水温稳定性,以及长期水环境下材料的抗拉性能和刚度,效果更为显著;粗集料含量由30%增加到40%,对于改善材料在可溶盐腐蚀环境下的抗拉性能和刚度,效果更为显著。     

坡顶荷载作用下废旧轮胎条带加筋边坡承载特性

为揭示废旧轮胎条带加筋边坡的承载特性,确定关键影响因素,开展坡顶竖向荷载作用下废旧轮胎条带加筋边坡承载特性模型试验与数值模拟分析,研究加筋层数、条带长度、间距等因素对边坡承载力、沉降与侧向变形的影响规律。结果表明：相比较自然填土边坡,废旧轮胎条带加筋边坡可有效改善边坡内部应力,增强加筋边坡的侧向约束效应,进而提高边坡的竖向受荷承载能力及边坡稳定性,提高幅度随加筋层数的增多而近似线性增大。随着条带长度的增加,加筋边坡的竖向承载能力得以提高,但当长宽比L/B≥4时,承载能力趋于稳定。废旧轮胎横向及竖向间距对加筋边坡极限承载力具有一定的影响,但提高幅度不显著,设计时可在合理控制范围内取较大间距。研究结果可为废旧轮胎条带在加筋土边坡中的工程应用与设计提供良好的借鉴意义。     

基于TDA填料的废旧轮胎条带加筋砂土边坡承载特性

基于废旧轮胎良好的抗拉伸、耐老化及界面粗糙等特性,将废旧轮胎切割成条形成加筋条带,并以轮胎衍生集料作为回填材料,形成复合加筋边坡。结合粒子图像测速技术进行模型试验研究,建立数值模型研究不同加筋条件下的边坡力学响应。探讨轮胎条带层数、加筋位置、废旧轮胎集料(tire-derived aggregate, TDA)复合土加筋层厚度与荷载作用位置对边坡承载力的影响,得到加筋效果随加筋布置方式的变化趋势。结果表明,轮胎条带和TDA复合砂土均可起到良好的加筋效果,且复合加筋边坡承载力相比无加筋提高2倍左右。研究结果证实了采用轮胎条带-TDA复合加筋边坡的可行性,为进一步进行废旧轮胎在道路工程中的循环利用研究工作和工程应用提供了基础。     

不同含泥量风积沙的压实特性试验研究

为研究不同含泥量风积沙的压实特性,确定适合路基填料的风积沙,采取风积沙试样,制备7种不同含泥量的风积沙,运用重型击实法、干振法和水振法进行试验.试验结果表明,含泥量在8%以下的风积沙适合用水振法确定最大干密度,含泥量在8%以上的风积沙适合用重型击实法确定最大干密度,干振法确定最大干密度效果最差.含泥量为16.5%～30.2%风积沙的干密度接近最大值,压实特性最好,适合作为路基填料.     

压实黏土膨胀与收缩特性试验研究

为了研究压实黏土遇水膨胀与失水收缩特性,开展了压实黏土的膨胀与收缩试验。试验结果表明,土样的压实度和初始含水率对其膨胀与收缩影响显著。压实黏土样的膨胀量随浸水时间延长基本呈现“S”型增大。压实黏土的干缩在初期属于正常收缩;在失水干缩后期,干缩体积小于失水体积,收缩量随时间变化为下凹型曲线;最后进入稳定的零收缩阶段。压实密度越大,收缩率越小;初始含水率越高,收缩率越大。压实黏土的干缩变形具有显著的各向异性。此研究对干旱及半干旱地区黏土干缩开裂机理的研究提供理论基础。     

新型轮胎静特性试验台的开发调试及其在轮胎特性研究中的应用

介绍了最近开发成功的新型轮胎静特性试验台的性能、结构、测试方法、控制及数据处理软件，并进行了实际测量。指出了该试验台的优点及其在轮胎力学模型研究中的重要作用。     

Vibration compaction characteristics of rock filling embankment

The dynamic model experiment of the rock filling embankment was carried out to investigate the vibration compaction mechanism. The rock filling materials were compacted by the plate-vibrated compactor, and the characteristics of the rock filling materials, such as settlement, pressure change and response waveform, were measured by the dynamic earth pressure gauge and accelerometer. Moreover, a new method for detecting the compactness of the rock filling embankment was proposed based on the maximum dry density and modulus of deformation. The results show that the process of vibration compaction includes compact, elastic deformation and loose stages, and the vibratory pressure transfers to the surroundings from the vibration center in non-linear rule. Furthermore, the test results obtained by the present method are basically in agreement with those obtained by the traditional method, and the maximum relative error between them is about 0.5%.     

Ability of rotary compactor in compacting consistent slabs and effect of rotary compaction on engineering properties of stone mastic asphalt mixtures

A new automatic rotary compactor and its abilities in compacting stone mastic asphalt （SMA） are presented. Following an overview of the rotary compactor and the compaction procedure, it is demonstrated that the rotary compactor is able to produce uniform slabs with the desired thickness of 65 mm all over around. Furthermore, 132 cored samples from the rotary compactor had been compacted uniformly with approximately 4% optimum air void content. In addition, performance tests results indicate that the rotary compactor produces asphalt mixturures with the requirements of resilient modulus, Marshall stability and flow. A weight factor was introduced for each fraction of aggregates in the degradation analysis to compensate the crushing effect of aggregates during mixing and compacting.     

水气分离集成井降水强夯法试验研究

为了克服降水强夯法处理深度小、降水时间长的缺陷,结合扬中灏港通用码头软土地基处理工程,改进了传统降水强夯工艺,采用水气分离集成井降水联合强夯法进行加固处理。通过在常规真空井点降水强夯和改进降水强夯两个试验区开展现场监测和检测试验,对加固效果进行了对比评价分析,研究结果表明:水气分离集成井降水强夯工艺降水深度可达地表以下5~6 m,夯后孔压消散时间约为1~2天;地基加固后总地表施工期最大沉降量为0.606 m,可有效减小工后沉降;与常规井点降水强夯法相比,改进法加固后土体强度和地基承载力均有较大提高,地基加固效果优势明显。     

Effects of warm compaction on mechanical properties of sintered P/M steels

The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pressures using polytetrafluoroethylene(PTFE)emulsion as the die wall lubricant.The effects of warm compaction on the mechanical properties were studied.The tensile fracture behaviors of cold compaction and warm compaction were studied using scanning electron microscope(SEM).The results show that the density of sintered P/M steel prepared by warm compaction or warm compaction with DWL is higher than that by cold compaction under all compaction pressures.Meanwhile,the highest tensile strength is obtained by combination of warm compaction and die wall lubrication under all compaction pressures.The SEM results show that the fracture modes of the sintered samples prepared by cold compaction and warm compaction at 700 MPa are the mixed mode of ductile fracture and brittle fracture,and obvious dimples can be found in some regions.The fracture of sample prepared by cold compaction is uneven and has irregular and big pores,but that by warm compaction is relatively even and the pores are round mostly,and the samples have many obvious dimples on the whole fracture surface.     

Experimental study on the mechanical properties of rocks at high temperature

The mechanical properties of marble, limestone, and sandstone as well as the stress-strain curve, the varying characteristics of the peak strength, the peak strain and elastic modulus were studied by using the MTS810 Rock Mechanics Servo-controlled Testing System under the action of temperatures rang- ing from room temperature to 800℃ . Results show that (1) the peak strength and elastic modulus of marble fluctuate at the temperature from normal to 400 ℃ ; and they decrease gradually over 400℃ . (2) With th...     

热处理过程对锦纶6帘子线性能的影响

针对锦纶6帘子线易收缩、强度低等性能方面的不足，对其戍品纤维再次进行热处理试验，以研究纤维收缩机理和规律，进而明确工艺调整方向．研究认为，热处理温度、时间、张力是其收缩率的主要影响因素，并且也依赖于纤维解取向程度和结晶度的大小．根据这种设想，在实验室中已获得了收缩率小于4％、强度为7．3cN／dtex、断裂伸长率为22％的锦纶6帘子线。     

动摩擦特性对轮胎侧偏、纵滑复合特性的影响

将轮胎橡胶的动摩擦特性应用于侧偏、纵滑复合工况下的统一刷子轮胎模型中,分析了动摩擦特性参数对复合轮胎模型的影响,建立了附着区、滑移区剪切应力方向角,推导了考虑动摩擦特性的复合特性力学表达式,建立了可实现不同速度、不同路面及任意侧向、纵向摩擦特性下仿真的理论模型。     

风化岩基大直径灌注桩后注浆承载性能试验研究

基于6根全风化和强风化花岗片麻岩地基中大直径泥浆护壁钻孔灌注桩单桩竖向抗压静载荷试验及桩身力学测试,对其中3根试桩进行桩侧后注浆,对比分析了其承载性状、变形特性及影响因素,并将所得试验数据与勘察报告推荐值和现行规范推荐值对比。结果表明：大直径嵌岩泥浆护壁钻孔灌注桩长径比25~34与嵌岩深度5D~8D,Q-s曲线呈缓变型;经后注浆处理与未经桩侧后注浆处理的试桩相比,单桩极限抗压承载力提高1.40%~15.3%,最大沉降量降低35.1%~65.6%,回弹率提高13.1%~82.4%,控制桩顶沉降效果显著。在该试验条件下,6根试桩的承载力和变形特性受长径比和嵌岩深度影响较大。经桩侧后注浆处理的试桩,嵌岩段摩阻比和桩侧摩阻力分担比受长径比和嵌岩深度影响更小;6根试桩的桩端阻力分担比受嵌岩深度影响显著;未经桩侧后注浆处理的试桩,桩侧摩阻力分担比受嵌岩深度影响更大。     

地铁隧道基底饱水风化软岩动力特性试验研究

为探究在列车长期循环荷载作用下地铁隧道基底风化软岩的累积塑性应变变化规律,以南昌地铁基底泥质粉砂岩为研究对象,开展不同风化程度饱水泥质粉砂岩在动应力比、静偏应力比、围压和频率等工况的室内动三轴试验,研究在不同影响因素下饱水风化泥质粉砂岩的动力变形特性规律。结果表明：在不同影响因素下,全、中风化泥质粉砂岩累积应变分别在加载1 000、100次开始趋于稳定;全风化泥质粉砂岩的临界动应力比在0.3~0.4之间;与不同动应力比和静偏应力比情况相比,改变围压和频率对两种风化泥质粉砂岩累积应变影响不大;通过分析试验结果数据,提出考虑加载次数、动应力比等因素的累积塑性应变数学模型。     

Fatigue properties analysis of cracked rock based on fracture evolution process

Fracture evolution process (initiation, propagation and coalescence) of cracked rock was observed and the force- displacement curves of cracked rock were measured under uniaxial cyclic loading. The tested specimens made of sandstone-like modeling material contained three pre-existing intermittent cracks with different geometrical distributions. The experimental results indicate that the fatigue deformation limit corresponding to the maximal cyclic load is equal to that of post-peak locus of static complete force?displacement curve; the fatigue deformation process can be divided into three stages: initial deformation, constant deformation rate and accelerative deformation; the time of fracture initiation, propagation and coalescence corresponds to the change of irreversible deformation.