Advanced Materials Research Vols. 255-260

Abstract: Inconstruction process of mass concrete is apt to form excessive temperature stress and cause mass concrete cracking, because of its high inner temperature, big internal and external temperature difference. In order to prevent their cracking, in mass concrete of the internal Settings with cooling water pipe cooling is one of the commonly used massive concrete construction method. This paper presents a massive concrete design of cooling water cooling and calculation theory, based on the cooling pipes in concrete heat transfer performance, through the cooling water pipe and concrete heat exchange principle.

Abstract: After foundation excavation for a dam of a hydropower project, the rock mass would be unloaded and relaxed and its mechanical parameters would be lowered, thus influencing the dam stability. This paper makes an analysis of the deformation development law of the unloading rock mass of the dam foundation by analyzing the advance deformation of the dam foundation before excavation and the unloading rebound deformation of the dam foundation after excavation, and by analyzing the monitoring results of the compressive deformation after concreting of the dam and of the whole process deformation after impounding of the reservoir taking into account the results of both deformation test and acoustic test, which provides scientific basis for quality assessment of the arch dam foundation rock mass and for readjustment of the dam foundation rock mass mechanics design parameters, thus giving a reference to projects of the kind.

Abstract: Based on the data of water depth in the South Branch and the Hengsha Passage, and the flow spilt ratio of the North Passage and the South Passage, the reasons for the sediment deposition in the upper reach of the Deepwater Navigation Channel in the Changjiang River Estuary are explored. The study shows the influence of the development of the Hengsha Passage is significant. The development of Hengsha Passage causes the increase of sediment and water exchange between the North Channel and the North Passage, which weakens the sediment and water exchange between the North Channel and the North Passage, and enhances the sediment silting in the upper reach of the Deepwater Navigation Channel. The development of Hengsha Passage also causes the scour of the upper reach of the South Passage, which weakens the ebb tide entering into the North Passage and further strengthens the sediment deposition in the upper reach of the Deepwater Navigation Channel. On the other hand, the Coriolis force and V-shaped diversion dike at the head of the Deepwater Navigation Channel also contribute the sediment deposition in the upper reach of the Deepwater Navigation Channel.

Abstract: Fluvial action is the most universal erosion process in geological history. Rivers in the surface of the Earth had molded different kinds of geomorphic features and varied landforms; also they had great effect on the human beings. Evaluating the fluvial landforms correctly and objectively will help people to exploit the living space adequately and utilize natural environment reasonably. Moreover studying on the spatial distribution of the rivers in a local area will help people to understand the situation of the river at present and forecast the development of the river in the future. Fractal and multi- fractal theory is a new and developing subject in modern science; it is widely used in many fields of earth science. Static Cone Penetrate Test is an exploration technology which can obtain the physical indices of soil. A study had found that specific penetration resistances varied with the buried depth of the strata and the curves of test values have characteristics of fractal. In this paper, with the assistance of fractal and multi-fractal theory, we analyzed the simple dimension and multi-fractal properties of these curves. Results suggested that simple dimension as well as the multi-fractal spectrum can tell the difference between the soils deposited in distinct sedimentary environments.

Abstract: The developed groundwater pipe network drainage system in the gravel soil slope has a significant impact to its stability. Considering the underground water level monitoring result, this paper simulates the xikengkou slope after the excavation and rainfall conditions based on fluid-solid coupling. The result presents that excavation at toe of slope damaged the groundwater discharge path. In the rainfall condition, the groundwater level increases significantly, which leads displacement occurring within the gravel soil slope. On the other hand, the displacement makes the drainage system be further destroyed and the permeability coefficient continues decreasing. Finally, the high water table leads the slope stability decreasing considerably, even to instability.

Abstract: The heat(cold) caused by atmospheric temperature flows backward during construction period makes the temperature field and the stress field of concrete change a lot, and we have to take relevant measures when the change influence the crack resistance of concrete. Based on the causes and the change-principium of thermal stress, we use ANSYS software to analyze the influence on temperature field and the stress field of concrete that caused by atmospheric temperature, and find some measures to protect the concrete from excessive temperature stress.

Abstract: With its good spanning capacity and whole structural stress performance, the prestressed concrete box girder is widely used in modern large-span bridge structures. But, if the construction of box girder prefabricated control is inappropriate, cracks will appear easily, thereby the structure stability and durability will be greatly influenced. Through analysis of concrete box girder constituent materials, pouring temperature, construction process, and according to correlative concrete anti-cracking theories and analysis, there comes the prestressed concrete box girder crack preventative measures and repairing technic.

Abstract: The hydration coefficient of cement is the main influence factor of the cumulating quatity of internal heat. It directly affects temperature-rise of the concrete and the variation in temperature stresses of mass concrete, to a certain degree, control occurring of the mass concrete cracks. So,it is the main content of construction management of mass concrete. According to the root cause which lends to mass concrete cracks occur, we have analyzed the influence of hydration coefficient on mass concrete temperature stress by the large finite analyzing software ANSYS, and drawn the corresponding conclusion.

Abstract: Reducing emitters’ working hydraulic pressure appropriately can cut down construction cost and running cost of the whole drip irrigation system. Reduction of the emitters’ working hydraulic pressure, however, will directly affect emitters’ hydraulic characteristics and anti-clogging property. In this study, experimental research into the hydraulic characteristics of multiple types of emitters under micro-pressure and compared the hydraulic characteristics with the ones under normal hydraulic pressure has been done. The experimental results showed that compensating emitters had poor water discharge uniformity at critical startup hydraulic pressure while non-compensating emitters, dripping arrows and dripping tape had consistent water discharge uniformity under micro-pressure and under normal pressure.

Abstract: The water forces acting on spur dike were systematically analyzed under the different influenced factors (flow discharge, water depth, bottom slope, length of spur dike). The results indicate that : ①the total pressure decreases with increasing flow, increases along with the water depth basically assumes the linearity to increase; ②the fluctuation pressure decreases along with the water depth and dike length increases, increases along with the discharge increases on each sampling points. The research results may not only be of great significance in understanding spur dike scour and destruction mechanism, but also provide a valuable reference for the design of spur dike.