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1.
研制了 30 0双向自调导叶透平试验机组 ,安装在 10 0 0活塞式往复流透平试验台上 ,对两种叶轮方案和 6种不同喷咀、扩压器进行了不同活塞行程、不同周期和不同恒定输出电压下性能试验。试验结果表明在喷咀出口角α1=2 1 5°、扩压器入口角α2 =6 5 5°和α1=2 4°、α2 =6 3°组合最佳 ,最高效率达 5 3 3% ,而且在宽广流量系数范围内 ,特别是大流量系数范围内都有较高效率。大大优于常用对称翼透平。将上下游导叶固定 ,变成双向固定导叶透平。用No 1叶轮和 6种导叶出口角组合进行试验。表明最佳导叶出口角为 2 4°～ 30°,最高效率仍达 38 5 % ,比对称翼透平仍高许多 相似文献
2.
根据下立交区间基坑特点,合理制定基坑工程降水方案。经工程实践证明,通过疏干井、混合井、降压井的合理设置,联合使用,科学有效地治理了地下水,较好地控制了因降水产生的工程风险。 相似文献
3.
Consideration of groundwater is a key element in almost every construction project. The design of deep excavations for basements or underground railway station concourses below the water table require that the water pressures are taken into account. Whilst these can be considered to be hydrostatic in soil, the decreasing permeability of rock with depth and the fact that groundwater flow is invariably along discrete fractures means that the water pressure is unlikely to be hydrostatic at depth.
Groundwater control for deep excavations can be achieved by a number of methods such as grouting, pumping or structural walls or a combination of these. For tunnelling projects grouting is extensively used, but the development of sophisticated tunnelling machines has led in many cases to the demise of compressed air as a means of groundwater control. 相似文献
4.
Numerous studies have been devoted to the performance of excavations and adjacent facilities. In contrast, few studies have focused on retaining wall deflections induced by pre-excavation dewatering. However, considerable inward cantilever deflections were observed for a diaphragm wall in a pre-excavation dewatering test based on a long and narrow metro excavation, and the maximum deflection reached 10 mm (37.6% of the allowable wall deflection for the project). Based on the test results, a three-dimensional soil–fluid coupled finite element model was established and used to study the mechanism of the dewatering-induced diaphragm wall deflections. Numerical results indicated that the diaphragm wall deflection results from three factors: (1) the seepage force around the dewatering well and the soil–wall interaction caused the inward horizontal displacement of the soil inside the excavation; (2) the reduced total earth pressure on the excavated side of the diaphragm wall above approximately 1/2 of the maximum dewatering depth disequilibrated the original earth pressure on both sides of the diaphragm wall; and (3) the different negative friction on the excavated and retained sides of the diaphragm wall led to the rotation of the diaphragm wall into the excavation. 相似文献
5.
深厚强透水含水层超大基坑降水群井效应研究 总被引：1，自引：0，他引：1
基坑减压降水的幅度与群井效应密切相关。某超大面积基坑,含水层组厚40m,中下部透水性强,采用非完整井降水。对水文地质条件概化,建立了地下水三维非稳定流数值模型,对均匀布置群井、不均匀布置群井、分块开挖降水、不同的井结构、布设回灌井等工况,进行了渗流场模拟。研究表明,强透水性含水层超大面积基坑降水的群井效应极为明显;井位角密中疏布置,可实现降深调平,避免降深不足和超降;基坑分块降水,可减少坑外降深;短滤管井结构可减少基坑总涌水量和坑外降深;强透水性含水层可灌性强,回灌对减少坑外水位下降有较明显的效果。模拟结果与现场监测较为一致。研究成果可为类似工程地下水控制设计提供参考。 相似文献
6.
At present, most calculation results regarding foundation pit dewatering are ideal values, making construction resources prone to being wasted. In order to optimize the traditional pipe well design of large wells, the linear programming solution module in Excel is used, with the total water inflow taken as the objective function, the water level drawdown used as the constraint and test condition, and a station project on the Chengdu Metro Line 7 serving as the subject of this study. The total water inflow of the traditional pipe well design is optimized by the simplex method, producing a total water inflow of 4 040.65 m~3/d, which, compared with 4 829.79 m~3/d, the total water inflow calculated by means of the traditional design optimization method, engenders a reduction of roughly 16% per day. The feasibility of the optimization methodology is verified by the drawdown constraint, which reveals the decrease of construction costs and the diminution of the influence that the lowered groundwater level has on the surroundings of the metro station. Finally, references are provided as to optimizing the dewatering designs for other metro stations in similar engineering and hydrogeological conditions. 相似文献
7.
大口径管井降水方法是应用较为广泛的、成熟的地下水控制措施。但因施工准入门槛低,在土建施工造价中所占比重较小,往往得不到重视,常出现边坡失稳、底板隆起等重大损失。基于抽水试验成果完成方案设计,抓准施工质量关键点是实现良好降水效果的必要条件。 相似文献
8.
Jörg Kröchert Elmar Buchner Luis I. González de Vallejo 《Marine Geophysical Researches》2008,29(3):177-184
Tubular-shaped concretions and concretionary dykes occur in Holocene fossil beach deposits between the township of El Médano
and Punta Roja in southern Tenerife, Canary Islands. These sediment structures have been interpreted either as the result
of (a) the interaction between hot ignimbrites that overflowed wet beaches; (b) fast accumulation of beach sands on hot and
degassing ignimbrites; (c) paleoliquefaction caused by an earthquake (seismites). Based on the interpretation as seismites,
an intense paleoearthquake with a moment magnitude of M = 6.8 was proposed to be responsible for the generation of the paleoliquefaction structures. However, we here reinterpret
the sedimentary structures in question using the general criteria diagnostic for rhizocretions and root tubules with respect
to their orientation, size, branching system, and style of cementation and, thus, consider them, to be of biogenic origin. 相似文献
9.
The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions. Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow. Therefor 相似文献
10.
The performance of the contra-rotating Wells turbine installed in the LIMPET wave power station is compared to the predicted performance from theoretical analysis and model tests. A reasonable agreement was found between the predicted and measured turbine damping characteristic, however the turbine efficiency was found to be poorly predicted. It is postulated that this is due to the unsteady nature and mal-distribution of flow through the LIMPET turbine, which were not considered in the predictions. It is suggested that the reduced performance of the contra-rotating Wells turbine makes biplane or monoplane Wells turbines with guide vanes better solutions for OWC's. 相似文献