初始静孔隙水压力对砂土静动力剪切特性影响的试验研究

选取福建标准砂和滹沱河细砂,利用空心圆柱扭剪仪开展了一系列不同初始静孔隙水压力条件下的不排水循环扭剪试验和单调扭剪试验,着重探讨初始静孔隙水压力对超静孔隙水压力发展及其不排水抗剪强度的影响。试验结果表明:初始静孔隙水压力对超静孔隙水压力的发展产生显著的影响,从而影响砂土的静动力剪切特性。具体地,在不排水循环剪切过程中,初始静孔隙水压力越大,其超静孔隙水压力发展和变形发展越快;在不排水单调剪切过程中,初始静孔隙水压力越大,在砂土剪胀阶段产生负超静孔隙水压力越大,从而使砂土的强度显著提高。基于试验结果,初步探讨了初始静孔隙水压力对超静孔隙水压力及静动力剪切特性的影响机理。研究表明,研究地下水位以下土体(准饱和土)静动力剪切特性尤其是研究液化问题时,应充分考虑初始静孔隙水压力对砂土抗液化强度的影响,室内试验应根据砂土所处的地下水位深度来决定初始静孔隙水压力(反压)的大小。     

油井爆生气体对岩石劈裂作用机制探索

油井爆生气体对岩石劈裂作用过程，是裂缝面对动态荷载响应并使其发生动态扩展的过程。为描述裂缝动态扩展过程，在气体劈裂过程各能量平衡关系式中，引入动能增量。而动能增量可由量纲分析法推导的能反映裂缝扩展速度和加载率影响的计算公式表示。在离散时间域内，特定气体劈裂作用下，能量方程迭代求解可得到裂缝扩展速度及裂缝扩展长度。由算例分析可知，虽然气体升压变缓时裂尖动态响应对裂缝扩展影响有减弱的趋势，但在气体压力升压较缓情况下，裂尖动态响应对裂缝扩展结果影响仍然很显著。     

A neural network evaluation model for individual thermal comfort

An evaluation model for individual thermal comfort is presented based on the BP neural network. The train data came from a thermal comfort survey. The evaluation results of the model showed a good match with the subject's real thermal sensation, which indicated that the model can be used to evaluate individual thermal comfort rightly. Taken a room air conditioner as an example, the application of the NNEM in creating a microenvironment for individual was discussed. The result showed that the NNEM can play an important role of connecting individual thermal comfort with the control on the air conditioner.     

循环冷冲击作用下煤的渗透性变化规律试验研究

为了研究循环冷冲击处理对煤体增透作用的影响,利用SLX-80型高低温处理系统对原煤煤样进行多次循环冷冲击处理,并利用电子天平和三轴瓦斯渗流实验系统分别测定了煤样冷冲击处理前后的质量变化和渗透率增加幅度,对比分析了冷冲击处理前后煤样表面的裂纹分布情况。试验研究结果表明,循环冷冲击处理所产生的热应力超过煤体抗拉强度时会在煤体内部形成新的裂缝,增加原始裂缝的有效宽度,从而提高了煤体内部裂缝连通的有效性,有效改善了煤体渗透性;循环冷冲击处理后煤体渗透率的平均增幅为16%～215%,煤体渗透率增幅大小与处理后的裂纹增加数量及其连通性紧密相关;煤岩材料的非均质性、外部应力载荷及“负损伤”效应的影响使得循环冷冲击处理后的煤体渗透率增幅具有明显的随机性,并呈现出非均匀波动变化特征;循环冷冲击处理所产生的收缩-膨胀效应会引起煤体部分碎块脱落,最终导致煤体质量减小,循环冷处理后煤体的平均质量减幅为0.151%。     

水泥土搅拌桩加锚杆围护结构的变形计算

基坑围护结构的变形大小直接关系到围护结构的可靠性 ,影响到围周建筑、道路和地下管线的安全 ,因此计算基坑开挖引起土体和围护结构的变形是一项重要课题。本文推导了水泥搅拌桩围护结构变形计算的刚性墙—弹性地基法的解析式 ,研制了基于弹性墙—非线性弹性地基法有限元计算程度CPWALL ,并结合广州市广园东路铁路职工住宅大楼水泥搅拌桩基坑围护工程进行了应用研究 ,计算分析表明弹性墙—弹性地基有限法能较好地反映工程实际情况。应用该计算程序 ,根据基坑开挖过程中阶段性位移实测结果可通过反分析确定地基系数 ,并对是否设置土层锚杆、加长土层锚杆控制位移、预测最大位移等工况进行了应用研究     

基于遗传算法的SMW围护结构水泥土刚度系数计算

SMW工法是水泥土搅拌桩内插H型钢的复合围护结构,其结构主要包括水泥土和芯材两大主要部分。围护结构的受力特性非常复杂,型钢的物理力学性质在施工过程时应力水平下比较稳定,基本处于线弹性范围,而水泥土的应力应变特性呈现明显的非线性特性,围护结构的刚度变化主要是水泥土的刚度变化。由于试验数据与工程经验还很有限,准确确定水泥土的刚度贡献值存在一定困难。本文引进遗传算法,在深基坑工程底板浇筑完成时各测点位移量测资料基础上,进行位移反分析,得到复合结构弹模Ecs与惯性矩Ics的优化取值,从而得出各测点在该工况下的刚度系数,该值与推荐曲线较为接近,说明反演分析的可行性。     

对单井回灌纳入某建筑标准设计的质疑

单井回灌一个致命的缺陷是“短路”,即回灌水未充分与土壤进行热量交换就又被抽了回去。这样,随着运行过程的进行抽出的井水温度夏天逐渐升高,冬天逐渐降低,导致投资高、运行效率低、运行费用高,而且在严寒时有无法运行的可能。对于这样一个有严重缺陷的系统纳入某建筑设计标准是不妥的。     

FRP加固混凝土梁的有限元分析

碳纤维复合材料(CFRP)加固混凝土结构是一种新型结构加固方法。在大比例模型试验的基础上,应用有限元程序对 T 型梁进行了加固分析,以研究 CFRP 布加固对混凝土梁抗弯能力及刚度的提高程度。分析结果表明,CFRP 布加固可应用于大型钢筋混凝土桥梁。     

Concentration du virus de l'hepatite a sur des membranes de celluloseHepatitis a virus concentration on cellulose membranes

Viral hepatitis type A is the most prevalent waterborne disease in U.S.A. and the number of cases has been increasing in recent years (Melnick et al., 1978). Till now, few works were performed on Hepatitis A Virus (HAV) concentration in water (Hejkal et al., 1982, Elkana et al., 1983). In this paper the filter adsorption-elution method, widely used with other viruses (Wallis and Melnick, 1967; Fields et Metcalf, 1975; Smith and Gerba, 1982), was selected to concentrate HAV from experimentally-contaminated distilled water. Filtration was performed through two cellulose membranes (RAWP 04700 and HAWP 04700 Millipore). Eluate or filtrate viruses were precipitated by polyethylene glycol 6000. HAV is detected by solid phase radioimmunoassay according to a previously described method (Deloince et al., 1982). Figure 1 shows the results of adsorbing HAV at different pH levels. Analysis of variance pointed out that, for the pH levels between 3 and 4, the differences were not significant (P = 0.05). Table 1 shows the effects of pH and number of passages of 3% beef extract or 0.2 M glycin buffer on HAV elution. For both eluents the differences in function of pH levels and number of passages of eluent through the membrane were not significant (variance analysis P = 0.05). On the other hand, the comparison between the two eluents pointed out the higher efficiency of beef extract (t-test, P = 0.001). After this procedure, HAV replication occurred in human hepatocarcinoma cells PLC/PRF/5 (Fig. 2) inoculated according to a previously described method (Crance et al., 1983). As poliovirus (Sobsey et al., 1973), HAV adsorption is the most efficient at acid pH levels. Between pH 4.5 and 5, the remarkable adsorption decrease might be related to the inversion of the HAV electrostatic charges sign, i.e. to the occurrence of an isoelectric point. The HAV elution is different from the poliovirus one, the efficiency of which increased with pH (Wallis et al., 1972) and eluent passage numbers (Farrah et al., 1976). That might suggest that from pH 7.5, both the HAV particles and membranes have negative charges which give enough repulsive forces to allow a good elution efficiency. Improvement of HAV elution efficiency by beef extract is similar to a result obtained with poliovirus by Landry et al. (1978). This effect might be explained by the proteinous material presence in beef extract. HAV replication in cell cultures shows the biological properties preservation after this procedure.     

三轴压缩条件下单裂隙花岗岩破坏特性研究

基于常规三轴压缩室内试验分析不同倾角和张开度的单裂隙花岗岩宏观破坏特性,进一步结合颗粒流离散元分析法,对裂纹扩展、能量转化等规律进行探究,结果表明:裂隙倾角α对岩石力学特性影响显著,随着α增加,弹性模量呈现单调增大趋势,同时三轴抗压强度表现出先减小后增大规律,在约60°时达到最小值;随着裂隙倾角的增加,岩石破坏模式逐渐由拉剪混合破坏向宏观剪切破坏转变;裂隙张开度增大,将导致岩石三轴抗压强度大幅下降,围绕初始预制裂隙形成更宽的破碎带;岩石破坏过程中,裂纹数量整体呈“S”型累积,其突变点与应力 应变曲线的弹、塑性和破坏特征点一致;能量耗散与细观劣化特征具有较好的相关性,岩石结构劣化及失稳破坏本质上是能量储存、耗散、释放的过程。