不同混合比橡胶砂动力性能试验研究

橡胶材料具有廉价、阻尼大、弹性变形较好等优点,将废旧轮胎颗粒加入路基填料中可在减少环境污染的同时提高路基抗震性能。本文通过橡胶砂基本物性试验和动三轴试验研究了不同混合比橡胶砂的减震性能,分析对比了不同混合比橡胶砂和纯砂的动弹性模量、阻尼比、动强度、内摩擦角及动应力－应变滞回曲线的变化规律。得出结论:橡胶砂动弹性模量受动应变影响较大,当动应变较大时橡胶砂的弹性模量大于纯砂;掺入橡胶颗粒可提高纯砂的阻尼比和动强度;实际工程应用中需要考虑橡胶砂混合比的影响。     

软土动力特性动三轴试验研究

许多学者对软土在动力作用下的变形特性进行了大量的研究,并提出了相应的经验公式,但其经验公式参数较多且试验复杂,不易被一般工程技术人员掌握运用。本文采用天津滨海地区软土为研究对象,进行钻探取样、波速测试、室内静力学和动三轴试验,获取该地区软土的静、动力学参数,并利用相对简单的模型对残余应变和软化指数随振次的变化规律采用最小二乘法进行拟合,取得很好的效果。成果表明,利用简单的模型对软土的动力特性进行区域性研究是可行的。该成果可为今后软土动力特性和软土震陷计算方法研究提供参考和基础性资料。     

土体动剪切模量及其衰减特性现场试验研究

如何获取土体动模量原位衰减曲线是研究天然土层在循环动荷载下的动变形特性课题中亟待解决的难题。为此,本文自制了一套地震动参数现场试验系统,依据动剪切模量原位测试原理获得了不同深度土体在小应变范围内的动模量原位衰减曲线。试验数据表明:当剪应变小于4×10^－5时,土体变形处于线性阶段;当剪应变大于4×10^－5时,土体归一化动剪切模量G/G_max衰减加快,以塑性变形为主。同时,当向土层施加的垂向静荷载越大,归一化动剪切模量值G/G_max与对数剪应变值logγ_d之间的关系会逐渐上移,但直线段斜率值不变。相关成果可为试验场地的动模量取值提供一定参考。     

强夯法加固夹砂粘土吹填场地的现场试验研究

江苏省连云港赣榆港区陆域采用航道和港池的疏浚土方吹填形成作业港区,吹填工艺以绞吸式疏浚为主,疏浚涉及土层为粘土和砂土,由此形成了粘土和砂土的混合土地基。为了提高地基承载力和均匀性,采用了强夯法对地基进行加固,但是目前对夹砂粘土地基强夯加固的理论和实践较少。为此,以砂夹粘土构成的混合土地基为对象,测试了多种能量单点夯击时的地基土夯沉量、孔压和夯坑周围土体强度等参数,探讨了强夯法加固该类地基的加固深度和水平影响范围。结果表明：对于该类地基而言,有效加固深度修正系数取0.35~0.5为宜;强夯过程中,孔压与强度的增长范围不对应,即孔压影响范围远大于强度影响范围。     

应力主轴旋转条件下各向异性云母砂变形的试验研究

实际工程中人工填土由于碾压的施工方法不同都存在不同程度的各向异性,在这些工程的不同阶段内部土体受力状态将发生变化,应力主轴会发生一定角度的偏转,导致诱发各向异性的产生。为了研究这种工况下,土体的变形特性,文中以固有各向异性较为明显的云母砂为研究对象,采用香港科技大学的自动控制空心圆柱扭剪仪进行了应力主轴连续旋转的循环扭剪试验,根据试验结果获得云母砂的诱发各向异性变形规律。     

砂-粉混合料剪切波速的弯曲元及共振柱试验对比试验研究

为探讨测试方法、试验条件以及级配特征对砂-粉混合料剪切波速的影响,对具有不同细粒含量FC,相对密度Dr以及初始有效围压$\sigma_{3 \mathrm{c}}^{\prime}$的砂-粉混合料进行弯曲元和共振柱试验。结果表明：当Dr =35%或50%时,剪切波速Vs随FC的增大先减小后增大;当Dr =60%时,Vs随FC的增大而减小;弯曲元试验测得的Vs明显大于共振柱试验测得的Vs,随着FC的增大,弯曲元试验与共振试验得到的Vs差值逐渐减小,而当FC＞20%时,两种试验得到的Vs基本相同。在考虑Vs弥散性之后,不同FC的混合料弯曲元与共振柱试验得到的Vs结果具有较好的一致性。基于Hardin模型建立的砂-粉混合料Vs预测方法具有较好的预测效果。     

先进土工实验技术研发与砾性土动力特性试验研究

<正>室内试验是解决土动力学问题的基本手段之一,同时室内试验技术也是土动力学的重要研究内容,为满足研究工作需求,需要不断研发新的技术手段。在2008年我国汶川大地震中,国际上首次出现了大规模的砾性土液化现象,而目前此方面研究报道尚少,其中砾性土动力特性研究是此方面的基础性工作。本文工作主要集中在两个方面,一是土动力学若干试     

Field evaluation of some sand transport models

Fluorescent tracer procedures, originally developed for research on fluvial sediment movement, were used to monitor the movement of three commercially purchased sands in a natural dune environment. Results were compared with estimates of transport rates from three theoretical models. Estimates from models by Bagnold (1941) and Hsu (1971) were larger by as much as one order of magnitude than the rates observed in the tracer study. The model of A. A. Kadib (1965) provided closer correspondence to observed transport rates for medium sand (mean diam. 0.653 mm) but underestimated rates for coarse sand (mean diam. 0.992 mm).     

Field observations of the vertical distribution of sand transport characteristics over fine,medium and coarse sand surfaces

The vertical distribution of sand transport characteristics is an important issue in aeolian research. Surface characteristics affect sand transport processes, but their effects are not yet fully understood. To provide more data on this subject, we observed sand transport in 16 field experiments above surfaces covered by fine, medium and coarse sand. The sand transport rate over relatively coarser‐grained medium and coarse surfaces could be expressed as a Gaussian peak function: q _z = a + b exp (?0.5[(|z – C _h|)/d ]^e), where q _z is the measured sediment transport at height z above the bed and a , b , C _h, d , and e are regression coefficients. The measured sand transport flux peak values (H _h) were linearly related to C _h, and both values were significantly related to the mean surface grain size. However, for the relatively finer‐grained medium and fine sand surfaces, the sediment transport could be expressed as an exponential function. The cumulative sand transport below 0.1 m was directly related to the mean surface grain size, and the relationship could be expressed as the following exponential function: C _z = f + g exp –M _z/i , where C _z is the cumulative sand transport at height z above the bed, M _z is the mean grain size and f , g , and i are regression coefficients. Above 0.1 m, there were no significant relationships between the cumulative sand transport and the mean surface grain size. The mean grain size decreased with increasing height below the peak height and then increased with increasing height. The surface grain size distribution and proportions of the particles in different grain size categories controlled the mean grain size as a function of height. The observed changes in the sand transport rate and grain size with height will provide support for sand disaster mitigation, numerical modelling and studies of dune formation. Copyright © 2016 John Wiley & Sons, Ltd.     

砂土液化中颗粒分析试验试剂用量标准的研究

采用不同剂量的六偏磷酸钠试剂，对GB／T50123—1999《土工试验方法标准》中的密度计法(甲种密度计)做颗粒分析试验的结果进行对比分析^[1]，由此对4％六偏磷酸钠溶液用量与分析结果的关系以及10m1的标准用量进行验证与探讨。     

Field test of the superconducting gravimeter as a hydrologic sensor

We report on a field test of a transportable version of a superconducting gravimeter (SG) intended for groundwater storage monitoring. The test was conducted over a 6-month period at a site adjacent to a well in the recharge zone of the karstic Edwards Aquifer, a major groundwater resource in central Texas. The purpose of the study was to assess requirements for unattended operation of the SG in a field setting and to obtain a gravimetric estimate of aquifer specific yield. The experiment confirmed successful operation of the SG, but water level changes were small (<0.3 m) leading to uncertainty in the estimate of specific yield. Barometric pressure changes were the dominant cause of both water level variations and non-tidal gravity changes. The specific yield estimate (0.26) is larger than most published values and dependent mainly on low frequency variations in residual gravity and water level time series.     

流动地震仪检测钻头振动信号的现场试验

钻井过程中钻头对井底的冲击振动为钻头前方地层的探测提供了震源,可用来消除钻井过程中的地质不确定性和降低钻井风险.本研究在分析井下钻头振动信号特点的基础上,根据现代地震观测技术的新发展,将多道勘探地震仪和流动数字地震仪的性能进行了对比分析,将天然地震的观测设备和分析方法应用到随钻地震检测中,提出了一套新的随钻地震检测方案,利用高灵敏度流动数字地震仪连续检测钻井过程中的钻头振动信号,初步现场试验表明该技术方案可行,获得的信号信噪比高,易于钻井工程师掌握,为随钻地震技术提供了新的技术路线.     

Modeling the response of shoreface-connected sand ridges to sand extraction on an inner shelf

Shoreface-connected sand ridges are rhythmic bedforms that occur on many storm-dominated inner shelves. The ridges span several kilometers, are a few meters high, and they evolve on a timescale of centuries. A process-based model is used to gain a fundamental insight into the response of these ridges to extraction of sand. Different scenarios of sand extraction (depth, location, and geometry of the extraction area; multiple sand extractions) are imposed. For each scenario, the response timescale as well as the characteristics of the new equilibrium state are determined. Results show that ridges partially restore after extraction, i.e., the disturbed bathymetry recovers on decadal timescales. However, in the end, the ridge original sand volume is not recovered. Initially, most sand that accomplishes the infill of the pit originates from the area upstream of the extraction, as well as from the areas surrounding the pit. The contribution of the latter strongly decreases in the subsequent time period. Depending on the location of the pit, additional sand sources contribute: First, if the pit is located close to the downstream trough, the pit gains sand by reduction of sand transport from the ridge to this trough. Second, if the pit is located close to the adjacent outer shelf, the ridge recovery is stronger due to an import of sand from that area. Furthermore, pits that are located close to the nearshore zone have a weak recovery, deeper pits have longer recovery timescales, wide and shallow pits recover most sand, while multiple sand pits slow down the recovery process.     

基山砂体沉积成因探讨

惠民凹陷是济扬坳陷主要生油凹陷之一,是典型的陆相断陷盆地。基山砂体是惠民凹陷在断陷期发育的一套物源来自于西北部宁津凸起的三角洲一浊积扇沉积体系;分布范围广,横跨滋镇洼陷、中央隆起带和临南洼陷田家一带;主体沿着宿安沟呈西北向东南方向展布,在临商地区发育类型丰富的油气藏,具有巨大的勘探潜力。近年来基山砂体油藏勘探取得较大成功,但砂体的物源、沉积相一直是争论的焦点,本文主要针对这2点进行了探讨,并将研究结论应用于勘探实践中,取得了显著的效果。     

地震受损房屋结构自振特性测试

采用底部剪力法对结构进行抗震计算的重要一步就是确定结构的基本自振周期,抗震设计规范为此提供了自振周期计算和相应的折减方法。对于新建结构,规范经验公式是合理的,但对于地震受损结构,当需要进行抗震加固设计计算时,针对完好建筑结构给出的规范经验公式就不再适用。由于缺乏实测资料,无论是抗震鉴定标准还是加固技术规程,都没有给出可以参考的方法。作者在玉树地震后,利用环境脉动测试方法,对在玉树地震中受到破坏的20余栋不同结构类型的房屋建筑结构进行了现场测试,获得了这些受损房屋结构的实测基本自振特性,给出了对结构震害程度与结构自振周期变化之间关系的初步认识。为震损结构鉴定与加固设计提供了可参考数据,同时,实测结果也可为结构非线性分析方法的发展和结果的验证提供重要参考。     

液化场地土-地铁车站结构大型振动台模型试验研究

本文对浅埋于可液化南京细砂地基中的地铁车站结构进行了大型振动台试验研究,对部分试验结果进行了整理,分析了模型地基的加速度和振动孔隙水压力的反应规律。试验结果表明:在整个试验过程中,模型地基浅层土和地铁车站侧向附近地基土最容易发生液化;其次,随着振动台台面输入地震动峰值加速度的增大,离车站结构较远的侧向地基土和底层地基土再发生液化,而车站结构正下方的模型地基土最不容易液化。同时,在模型地基土发生液化后,地铁车站结构发生了明显的整体上浮现象。     

Development of a growth inhibition test with the marine and brackish water red alga Ceramium tenuicorne

The marine red macroalga Ceramium tenuicorne is cosmopolitan and naturally found in both brackish and marine waters. A growth inhibition test with this species can be carried out in salinities from 4 per thousand to 32 per thousand. The species is easily held in culture in the laboratory and the test can be performed in a completely defined medium. The robustness of the method is good with a CV of 14.6% of the controls. The EC calculations can be performed on linear regression on the length data. EC50 values of repetitive tests for zinc (20-33 microg Zn(2+)/l in 7 per thousand and 32-61 microg Zn(2+)/l in 20 per thousand) and copper (1.9-3.8 Cu(2+)/l in 7 per thousand and 7.9-13 Cu(2+)/l in 20 per thousand) show high sensitivity. This test is a good complement to any test battery with the purpose of estimating the hazard of substances to the brackish and marine environment.