宁夏东干渠冬季输水可行性初探

宁夏金积供水工程通过河东灌区东干渠输配水。随着供水量的日益增大，冬季进行补水已成为当务之急。为确保冬季渠道安全运行，解决渠道冬季运行过程中出现的问题，结合2010--2011年度运行情况进行了探讨，结论认为，冬季利用东干渠补水是可行的。     

混凝土大坝冻胀变形统计分析模型研究

通过对混凝土大坝冻胀变形机制的分析,本文对冻胀变形统计分析模型的冰冻因子的构成进行了改进,采用了定周期、定初始角的周期函数因子和气温滞后作用因子等两类因子构成冻胀变形的因子集.对丰满大坝坝顶廊道真空激光准直典型位移测值的模型分析表明,改进的统计模型具有以下特点:(1)拟合效果优于或接近传统模型;(2)模型的物理意义更为明确合理,可以较好地解释历年"双峰"现象.温度分量仅反映传统意义上的简谐温度场变化所产生的结构变形,温度分量的变幅及相位可以正常地得到反映;(3)可以对季节性冻胀的影响进行直接分析,对变化量值进行一定的估计;(4)与传统模型相比,冻胀模型回归结果中的水位分量、时效分量相差不大.从资料分析的角度来看,增加"冻胀因子"并未使问题复杂化.总体来看,本文所建立模型方法是有效的.对于冻胀问题较为严重的混凝土大坝如丰满,有必要采用考虑冻胀因子的模型进行分析,以了解及评价冻胀对变形性态的影响,对大坝老化评估也是很有意义的.     

漳泽水库上游护坡的冻害与防冶对策

以漳泽水库的上游护坡冻害及防治为研究对象,通过实际运行中存在的问题及采取的措施阐明此项工作的重要性并提出今后工作的重点及此项工作研究的方向.     

负温高强混凝土技术研究进展

回顾与总结了近十年来我国负温高强混凝土技术的研究状况与主要研究问题,涉及到负温高强混凝土的配合比设计、冻结模式、强度发展规律、抗冻临界强度、损伤过程、可靠度、防冻剂作用机理等问题,说明了我国冬期施工在这一领域中所取得的主要成果,并提出了供讨论用的负温高强混凝土今后的研究方向。     

板式换热器应用于制冷系统的故障分析

介绍了板式换热器应用于制冷系统时的几个问题：结垢，腐蚀，密封，冻裂，探讨了其防治方法，对使用维护具有指导意义。     

Observations of ice lens formation and frost heave in young Portland cement paste

As part of a research program to image frozen cement past specimens, abnormal microstructural formations are seen in specimens frozen after 10-h hydration. The formations are areas of loose microstructure with aspect ratios of 6-10, which appear perpendicular to the direction of cooling in the specimen. After sublimation of the water in the specimens during the imaging process, these formations collapse, indicating that ice is instrumental to their structure. These formations coincide with longitudinal cracks in the specimen, which do not appear to be due to specimen preparation and are consistent with an internal tensile strain. The authors have hypothesized that ice lens formation and frost heave, or a similar freezing mechanism, is responsible for these microstructural features, which are seen in 10-h specimens and are absent in all other cement paste specimens. Triaxial permeability tests have also shown that the cement paste mix used in this study has a permeability at 10-h age of ∼10⁻⁶ cm/s. This permeability is similar to that of silty soil, some of the most susceptible to frost heave.     

Calibration of model uncertainties in base heave stability for wide excavations in clay

In this study, the statistical properties for the model factor [the ratio of actual factor of safety (FS) to the calculated FS] of three popular base heave calculation methods are calibrated based on real case histories with wide excavation. The statistical properties of concern include the mean value and coefficient of variation (COV) of the model factor. It is found that the mean values of the model factors for the modified Terzaghi׳s and Bjerrum-Eide׳s methods are close to 1, whereas that for the slip circle method is significantly greater than 1. The COVs associated with the modified Terzaghi׳s and Bjerrum-Eide׳s methods are relatively low, while that associated with the slip circle method is relatively high. Based on the calibration results, reliability-based design charts are provided. It is concluded that the required factor of safety (FS) depends on two factors: (a) the target reliability index and (b) the COV of the calculated FS. For the case where this COV=10%, the required FS in codes for the modified Terzaghi׳s and slip circle methods (FS=1.5 and 1.2, respectively) seems reasonable. In contrast, the required FS for Bjerrum-Eide׳s method (FS=1.2) seems insufficient.     

冻土地区村镇给水管道保温层厚度数值计算简

我国冻土地区村镇给水管道冬季时常发生冻胀的现象,严重影响供水安全,对农民生产生活造成危害,亟需开展防冻技术研究.本文针对东北地区村镇供水实际情况,提出直埋管道外加保温层的防冻胀技术方法,并通过理论数值计算,确定出常用管材在不同埋深情况下的保温层厚度.     

封闭式可伸缩U形支架在底臌巷道中的应用

底臌巷道的治理有一定的难度,造成巷道底臌的原因也不尽相同,要治理好关键是要选择一种合理的支护方式和支架形式。湖南省煤业集团资兴祥和煤业有限公司,通过选择封闭式可伸缩U形支架的支护方式,最终成功地解决了底臌巷道的治理难题,为治理同类型的巷道积累了可贵经验。     

严寒地区道路冻胀的原因解析及防治措施

针对严寒地区道路易产生裂缝及产生隆起或下沉等破坏形式，分析了冻胀力对道路的影响，并从设计入手提出了采用保温、置换等解决道路破坏的具体方法，从而确保车辆通行和行车安全，延长道路使用寿命。