抗冻型商品砼在水工建物中的应用情况

近年来,水工建筑物的质量标准要求越来越高,商品砼成为建筑施工强制要求的施工原材料,因而其质量会对水工建筑物的质量产生直接影响。下文结合界圩河闸案例,对抗冻型商品砼的施工及质量管理措施进行探究,以供参考。

A study on dynamic response of slopes under wave action using simulation tests

After the erection of the Three Gorges Dam, the water level of Yangtze River will reach 175 m, and the average wave crest will be up to 1 m. Therefore the wave action cannot be neglected for the slope stability. Through simulation tests, the wave-induced dynamic response of the slope is analyzed. The soil body is taken as linear elastic body when it has a small deformation under the small wave action. Based on tests, the excess pore pressure and slope displacement under the loading in different wave period are analyzed. The ratio of dynamic strength and static strength to the breaking process of the slope is discussed. It is demonstrated that smaller wave period gives rise to a larger strain of the slope under the same stress. At different depth of water, different weakness effect on the stability of the soil slope is observed and the slope has an adaptability to the wave action to some extent.

Sediment Delivered in the Upper Part of Mosul Using Physical Model

Mosul dam is the biggest hydraulic structure in Iraq located on the River Tigris 60 km northwest of Mosul city. Its storage capacity is 11. 11 × 109 m3 and it had been in operation since 1986. A physical distorted model with movable bed having a vertical scale 1： 100 and a horizontal scale 1：1000 was used to conduct the experiments relating the water level at the reservoir and water discharge upstream the reservoir with the bed load transport rate. The model represents the first 15 km of most northern part of Mosul dam reservoir. The construction of the model was based on bathymetric survey conducted in 2009. Twenty-four experiments were executed using four different discharges （0.5, 1.0, 1.5, and 2.0 L/s） which represent the average discharges in the flood period of River Tigris. At each individual discharge six operations were assumed where the reservoir＇s water level was 305, 307, 309, 310, 312, 315 meters above sea level respectively. In all the experiments conducted, bedload transport was measured in the physical model at section representing the River Tigris 1 km upstream the reservoir. The results showed that the bedload rate was decreasing when the water level within the reservoir was increasing. It was also evident that bedload transport rate dramatically decreased at level 310 meters above sea level onward. This is due to the fact that at this level represent the effect of backwater which was noticeable on the river cross section

Slide stability of hydraulic structures on subbed soil

The study on slide stability of hydraulic structures on subbed soil was made. Using the slide test results of dragged concreting base plates on subbed soil pits, the decreased value of bearing capacity on slide after re- bound and repression influence of subbed soil was determined, and the envelope of ultimate slide shear resistance was also quantitatively determined. Due to the lack of similar mechanisms of slide stability on subbed soil and base plate of hydraulic structures, different safety coefficients for the slide stability were adopted. It was suggested to use the maximum compressive stress O＇m~ of eccentric load to predict structure displacement, slide and creepy slippage of subbed soil, to determine the sliding creepy contour and limit the maximum load on subbed soil. Two hydraulic structures that had been put into operation were reviewed by this method, and the results accorded with the real conditions.

Eco-drainage Pond in Non Irrigated Land for the Conservation of Land and Water Based on Community Participation

There are some bad impacts from a critical land such as flood in rainy season and dryness in dry season. Long dryness could cause shortage of water for human consumption, industry and agriculture. Prevention has been made to avoid the both bad impacts by building hydraulic structures like reservoirs and ponds in order to reduce the peak flow during the rainy season and to store the water for use during the dry season. However, they gradually become full of sediment. This will make them work insufficiently and will cause high maintenance cost. Moreover, wells in agriculture field used as retention also suffer dryness to make crop failure. This study aims to develop a model of pond for conservation of land and water in non irrigated land. Community participation is crucial in order to solve the flood and dryness problems. The community, especially the farmers will participate actively in the implementation and maintenance of the model. There are benefits in using the pond model such as： （1） to control sediment transport to the rivers, reservoir or other hydraulic structures; （2） to reduce flood rate; （3） to increase ground water recharge; （4） to contain water for agriculture and （5） to control the fertility of land. The cost of making a unit of model （sedrainpond） of 1.5 m diameter and 1.5 meter depth is relatively cheap between $10 to $20 （US）, and the maintenance is done by the farmers. When the pond model becomes functional, besides containing water in the rainy season, the water can be used to sustain water for agriculture in the dry season to avoid any crop failure. When the pond becomes dry, the farmers can harvest the suspended load sediment such as clay or silt to spread onto their land to keep its fertility.

Numerical Modeling of Local Scour Around Hydraulic Structure in Sandy Beds by Dynamic Mesh Method

Local scour, a non-negligible factor in hydraulic engineering, endangers the safety of hydraulic structures. In this work, a numerical model for simulating local scour was constructed, based on the open source code computational fluid dynamics model Open FOAM. We consider both the bedload and suspended load sediment transport in the scour model and adopt the dynamic mesh method to simulate the evolution of the bed elevation. We use the finite area method to project data between the three-dimensional flow model and the two-dimensional(2D) scour model. We also improved the 2D sand slide method and added it to the scour model to correct the bed bathymetry when the bed slope angle exceeds the angle of repose. Moreover, to validate our scour model, we conducted and compared the results of three experiments with those of the developed model. The validation results show that our developed model can reliably simulate local scour.

Concrete Erosion in Weak Sulfate Environment

The erosion failure mechanism of concrete is studied systematically based on field investigation and laboratory experiments of concrete samples from more than 30 km concrete lining and 10 hydraulic structures of Shandong Jiaodong water diversion project, in which the concrete failed only 3-6 months after conslruction was completed. With electron microscopy scanning, energy dispersive analysis, XKD （X-ray diffraction） analysis and Raman spectrum analysis of the mineral composition of the failure concrete and precipitates, chemical and physical reactions that occurred in the concrete under engineering environment were investigated. The analysis indicated that the rapid corrosion and dissolution reaction of the concrete in weak sulfate environment is due to sulfate and carbonate corrosion with the catalytic magnesium salt at low temperature. Also, corrosion damage facilitates the sulfate ions and carbonate ions into the concrete, and the expansion of ettringite and TSA （thaumasite sulfate attack） reaction also accelerates the corrosion damage of the concrete.

Study on Seepage Control in Complicated Hydrogeological Conditions on the Right Bank of JinPing-I Hydropower Station

With consideration of the special hydrogeological conditions and layout characteristics of the hydraulic structures, the seepage control measures of dam abutment and underground powerhouse on the right bank of JinPing-I hydropower station is drawn up. Based on the three dimensional finite element analysis of seepage control with dry area virtual flow constant mesh analysis method, the rationality of the seepage control measures of dam abutment and underground powerhouse has been verified and the key factors affecting the effect of seepage have been compared. In combination with the curtain of dam abutment, the curtain of underground powerhouse is reasonable. The results showed that the steel liner of penstock after the curtain is necessary.

Effect of air bubble size on cavitation erosion reduction

Over the past 60 years, the air concentration in water has been considered as a control index of cavitation erosion reduction and widely used in the designs of hydraulic structures. However, the mechanism of air entrainment against cavitation erosion has been paid good attention to. In the present work, the effect of air bubble size on cavitation erosion reduction was experimentally investigated. A device with micron-scale orifice diameters(10, 20 and 50 μm in size) was specially designed to introduce air bubbles into water. The experiments about the effect of air bubble size were conducted by means of a vibratory apparatus, including the behavior of formation and movement for single air bubble, the characteristics of cavitation erosion reduction at different air entrainment conditions. The findings demonstrate that high air concentration has significant effects on cavitation erosion reduction.But, a notable problem was that the size of air bubbles is of outstanding effect on cavitation erosion reduction. Small air bubbles support to alleviate cavitation erosion, even at same air concentration.