排序方式： 共有45条查询结果，搜索用时 31 毫秒
41.
Nowadays, self-compacting concrete is used in reinforced concrete structure with heavy bars. This type of concrete is widely accepted throughout the world; therefore, it can be used as an attractive solution for inner lining of tunnels. Regarding the effect of fibers in improving the concrete properties the effect of using polypropylene fiber on the behavior of arch specimens are investigated in laboratory. Therefore, specimens with dimensions of 1 m diameter, 0.5 m width, and 10 cm thickness with various reinforcing bars in arch forms were prepared and their flexural strength was investigated. The results show high ability of self-compacting concrete for the inner coverage of tunnels and its increasing strength is due to use of fibers. In addition, the results indicate that by adding fibers in the amount of 0.1 % of cement weight and reinforcing bars of size number 10, the required flexural strength would be obtained. 相似文献
42.
Kaveh Sookhak Lari John L. Rayner Greg B. Davis Colin D. Johnston 《Ground Water Monitoring & Remediation》2020,40(3):21-29
It is important to estimate what light nonaqueous phase liquid (LNAPL) recovery can be practicably achieved from subsurface environments. Over the last decade, research to address this included a broad field program, laboratory measurements and experimentation, and modeling approaches. Here, we consolidate key findings from the research in the context of current literature and understanding, with a focus on a well-validated, multiphase multicomponent modeling approach to achieve estimates of reasonable endpoints for LNAPL recovery. Simple analytical models can provide approximate saturation distributions and estimates of LNAPL recoverability via transmissivity approximation, but are insufficient to predict LNAPL saturation- and composition-based recovery endpoints for various recovery technologies. This is because they cannot account for multiphase, multicomponent fate and transport and key processes such as hysteresis. Recent advances to improve estimates of the fraction of recoverable LNAPL and its transmissivity are summarized. These advances include further development and application of a well-validated model to characterize active LNAPL recovery endpoints. We present key factors that affect the determination of LNAPL recovery endpoints, and outline how recovery endpoints are affected by natural source zone depletion (NSZD—currently gaining acceptance as a LNAPL remediation option). Major factors include geo-physical characteristics of the formation, magnitude of an LNAPL release and partitioning properties of the key LNAPL constituents of concern. Based on the capabilities of the validated model, the paper also provides a basis to optimize LNAPL recovery efforts. 相似文献
43.
44.
45.
Kaveh Pazand Ardeshir Hezarkhani Yousef Ghanbari Nasrin Aghavali 《Environmental Earth Sciences》2012,65(3):871-879
The chemical analysis of 59 water wells in Meshkinshar area, Ardabil province NW of IRAN has been evaluated to determine the
hydrogeochemical processes and ion concentration background in the region. The dominated hydrochemical types are Na–SO4, Ca–HCO3, Na–HCO3 and Na–Cl in the whole area. Based on the total hardness, the groundwater is soft. According to electrical conductivity and
sodium adsorption ratio, the most dominant classes are C1–S1, C2–S1 and C3–S1. The major ion concentrations are below the
acceptable level for drinking water. The groundwater salinity hazard is medium to high but the Na hazard is low to medium
and in regard of irrigation water the quality is low to medium. So the drainage system is necessary to avoid the increase
of toxic salt concentrations. 相似文献