On the basis of analyzing hydrogeological conditions, the spatio-temporal variation of hydrochemical characteristics of groundwater in Kuji water source area of Ordos basin is systematically researched. The chemical composition, spatial distribution, and variation of hydrochemical type were affected by geographic, geomorphic and runoff conditions. Results showed that hydrochemical type changed as a whole along the direction of groundwater flow from the peripheral watershed towards the interior and from the internal watershed towards the peripheral. The main negative ion gradually changed from HCO3 to HCO3•Cl and further HCO3•SO4•Cl, and then SO4•Cl. In vertical direction, close hydraulic connection between the middle layer and shallow layer groundwater was found, and their partition was not obvious. Due to close hydraulic connection in vertical direction for Cretaceous aquifer of huge thickness and the depth of groundwater, the groundwater quality is less affected by seasonal change.
The key to assess dam safety is to qualitatively evaluate each individual indicator. We determine the specific quantitative evaluation values of the dam safety level, and then define the model parameters of the dam safety level by non-linear fitting mathematical analysis tool (Matlab). Thereby, on the basis of Logistic model, we can get a precise quantitative evaluation model, which accurately fits the quantitative evaluation parameters with the determination coefficient of 0.998 6. In this way, the qualitative evaluation of individual indicators is transformed into quantitative evaluation.
Groundwater connectivity test was conducted to investigate the hydraulic connection between caves in the upstream and the downstream, and to quantitatively determine the ratio of water flow into the downstream caves. Rhodamine, which would be fluorescent illuminated by light of certain wavelengths, was used as tracer medium. Fluorescence spectrophotometer was employed to detect the intensity of fluorescence in the tracer solution, hence obtaining the curve of concentration vs. fluorescence intensity. The tracer was put at the entrance of Karst cave in the upstream, and water samples were collected at the exit in the downstream to detect the fluorescence intensity and measure the flow. According to the obtained curve, the tracer quality in the sample was calculated. Subsequently, the water allocation ratio was derived from the law of mass conservation and the theory of tracer transport and diffusion. Results showed that during the test period, 89% of the water flowed from caves in the upstream into the downstream. The relation between fluorescence intensity and tracer concentration is also believed to be feasible for quantitative analysis. The test method could be a reference for similar engineering practices.
The characteristics of cofferdam and foundation pit were analyzed. On this basis, the concept of seepage field regulation was put forward for cofferdam and foundation pit. The regulation aims at safety, construction period and cost control, as well as environment protection. It is emphasized that the efficiency can only be guaranteed by adequate and proper regulation measures at the right moment. The regulation measures were classified as preinstalled and urgent ones according to the time to take. Pertinent regulation measures and application conditions were presented. Furthermore, the importance of urgent measures when preinstalled measures failed was illustrated by an engineering example. The dynamic characteristics of seepage field corresponding to many factors were taken account into the seepage field regulation theory. With this theory, prompt and effective regulation measures would be arranged and fulfilled in the whole process through work planning, construction and operation to achieve aims inclusive of guaranteeing engineering safety, controlling construction period and cost, and mitigating negative effects on environment. Seepage field regulation theory is significant for all engineering involving surface and subsurface water.
A large number of cracks have made the deformation properties of rock mass become very complex. However, the effect of these microcracks is often neglected in the research of rock mass deformation properties using numerical simulation method. In order to make clear the effect of theses microcracks on the deformation parameters of rock mass, the deformation parameters of rock mass that contains one single microcrack are estimated based on equivalent deformation principle. Results show that the deformation characteristics of rock mass are related with the dip angle, the length and also the load orientation of the microcrack. When the length of the microcrack is longer, the deformation module of the rock mass is smaller and the Poisson ratio is bigger. When the intersection angle between the microcrack dip angle and the load orientation is smaller, the anisotropy of rock mass is more evident. Whereas with the increase of this intersection angle, the deformation moduli in different orientations are decreased, the Poisson ratios are increased and the anisotropy of the rock mass is weakened. When the intersection angle between the microcrack dip angle and the load orientation is 45°, the rock mass will be isotropic.
Through triaxial permeability tests and conventional permeability tests on reshaped Yangling loess of different dry densities, we analyzed the rules of permeability coefficient variation of the saturated loess respectively in gas-free pure water with pH=7.0, and acetic acid solution with pH=3.0, pH =4.0 and pH=5.0. We also investigated the degradation of loess permeated with acid solution. The research provides basis for analyzing the strength variation and the stability of loess structures permeated with acid solution. The results are as follows: (1) the permeability coefficient of saturated loess decreases with the growth of dry density; (2) with a constant dry density, the permeability coefficient reduces along with the increasing of confining pressure; (3) the largest permeability coefficient appears when the loess is permeated with acid solution with pH=3.0 in short-term, and with the rise of pH value, the permeability coefficient decreases as a result of the dissolving of insoluble salts by hydrogen ions of acid solution, forming new seepage channels. The permeability coefficient of pure water with pH=7.0 is between that of acid solution with pH=3.0 and pH=4.0. It is because that the pure water used in the test is boiled and gas-free, while there is small amount of gas in the acid solution for the test;(4) the permeability coefficient reduces with the increasing of time.
To research the strength characteristics, deformation properties, and failure regularities of sandy slate which has micro-bedding, triaxial compressed tests in loading and unloading conditions are carried out by MTS815 Flex test GT rock mechanics test system. The test results show that the peak intensities under loading are close to those under unloading condition when the bedding parallels to the maximum principal stress (parallel bedding). When the bedding is vertical to the maximum principal stress (vertical bedding), peak intensity and residual strength under unloading condition are respectively 20% and 25% lower than those under loading condition. The sandy slate with parallel bedding shows elastic brittle feature, and this brittle failure under unloading condition is stronger than that under loading condition. Failure surfaces of parallel bedding samples develop along the bedding planes direction, and the failure is caused by strong lateral expansion under tension. The failure faces of vertical bedding samples under loading condition display shear feature with diagonal transfixion plane, and the failure faces under unloading condition develop from the shear yielding planes at both ends to the center of the sample.
To explore the influence of the compressibility of reservoir water on the dynamic response, we carried out time-history analysis on the seismic dynamics of Wugachong arch dam using 3-D finite element model. Compared with the additional mass model, the model in the present study can better reflect the influence of reservoir water on the dynamic response. In the additional mass model, since the compressibility of reservoir water was not considered, the natural frequency of arch dam was lower and the hydrodynamic pressure was exaggerated. Changes of transverse and vertical displacements were little but the longitudinal displacement was increased, and the change of stress in arch direction was little while the vertical stress was increased.
The operation principle of POS (Position and Orientation System) is firstly described. Furthermore, problems need to be noted such as eccentricity component measurement, initialization of POS device, accuracy of data control and construction of base station are analyzed. Solutions and preventive measures are proposed in line with the requirements of practical aerial photography. The POS system has been used and tested successfully in several practices.
To tackle the difficulty of monitoring and statistically analyzing the grouting quality and construction schedule by traditional methods, we established a digital grouting management system by employing B/S network structure, in association with network technology, database technology and visual programming techniques. The system is to achieve real-time monitoring, data integration, data query, statistical analysis, and early warning for abnormal information. It can also integrate, manage and share the grouting data for engineers to acquire real-time on-site construction progress and to collect and analyze field information in time. The system would improve the grouting quality and provide support for decision-making.
The electrical conductivity of soil is controlled by the moisture content. With the voltage on both ends of the protective resistor in the circuit board as the signal to reflect the changes of moisture content, we designed a sensor for the moisture content. The sensors were calibrated in sand and sandy soil to obtain the linear variation relation between moisture content and voltage. The device is applied to the model of landslide induced by fog and rain infiltration to test the changes of moisture content. Results show that through this device we can get the moisture content variation conveniently, quickly and more accurately. It can meet the requirements of the landslide model test, but the infiltration relation and the influence of temperature were not taken into consideration. Further research and improvements are needed.
Cavitation erosion and abrasion will bring about damage, deformation, and crack to hydroturbine blades. A portable three-coordinate measuring machine was employed to repair the defects. Infinite 2.0 six-axis portable 3-D measuring machine was used as the hardware carrier. Software ScanWorks, Geomagic Studio, Geomagic Qualify and CAD were built in the machine. Through this measuring machine, reverse engineering scanning, 3-D spatial measurement, data visualization, 3-D modelling, point-cloud data analyzing and processing, and data conversion were carried out. By comparing the original 3-D model with the defective model, location and size of the defects were obtained. The three-coordinate measuring machine is accurate, and is of guiding importance for the repair of hydroturbine blades.
By traditional method of monitoring reservoir water temperature, the concrete temperature on the upstream surface of dam (which is measured by point thermometer inside the concrete) is taken as the water temperature. Errors are caused and the gauging points are limited. On the contrary, the distributed optical fiber (DOF) temperature measuring temperature system based on Raman scattering has resistance to EMI (electromagnetic interference), resistance to corrosion, electric insulation, high sensitivity, low cost, and can implement continuous spatial distributed measurement. We have applied this measurement system to the Three Gorges reservoir water temperature monitoring and studied its principle from perspectives of Optical Time Domain Reflectrometry(OTDR), Raman Scattering and scattering-light demodulation. Monitoring results show that the reservoir water temperature in front of the Three Gorges dam varies with atmospheric temperature with no obvious stratification along the water depth direction. The maximum average temperature is nearly 27℃ in August and the minimum is 10℃ in February.
The regularities and characteristics of the deformation of Maopingxi protective earth and rockfill dam in the Three Gorges are analyzed in the present paper. Data display that the internal cumulative settlement of the dam is 1.26m, about 1.21% of the dam height. The maximum external settlement is 205mm, and the maximum horizontal displacement is 85mm. The horizontal and vertical displacement values in the center of the river are great while at both banks are small. It's known that the horizontal and vertical displacement are irreversible. By means of statistical regression analysis, it is found that the horizontal displacement is affected by water pressure and aging effect, while the vertical displacement is mainly affected by aging effect instead of water pressure. The displacement rate of the dam has been decreasing year after year, but is still unstable. The dam is in normal working state.
