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Heat transfer within the soil is a complex process in the presence of seepage flow. In such conditions, the soil’s thermal behavior is influenced by the thermal and hydraulic properties of the medium as well as the initial conditions and boundary conditions to which the medium is subjected. This paper presents the experimental and numerical studies of heat transfer within the sand subjected to the seepage flow. It focuses on the influence of saturated hydraulic conductivity and the porosity of medium on the heat transfer process. The temperature distribution within the sand was monitored by the optical fiber Distributed Temperature Sensor (DTS). The experiment was performed on three types of silica-dominated sands with different saturated hydraulic conductivities and different Soil Water Characteristic Curve (SWCC). In addition to the experimental study, a coupled hydrothermal numerical model was designed in FEFLOW software and validated by comparing its results with the experimental measurements. To determine the influence of porosity and saturated hydraulic conductivity on heat transfer, we analyzed the numerical models for different values of porosity and saturated hydraulic conductivity. The numerical and experimental studies showed that the thermal velocity is higher in sand with higher saturated hydraulic conductivity and temperature declination occurs more quickly due to the heat convection process. Saturated sand with larger porosity has an overall higher heat capacity, wherefore the temperature declination started later in the measuring points but dropped down lower close to the temperature of the upstream water. Přenos tepla v půdě je složitý proces za přítomnosti prosakujícího toku. Za takových podmínek je tepelné chování půdy ovlivněno tepelnými a hydraulickými vlastnostmi média, jakož i počátečními podmínkami a okrajovými podmínkami, kterým je médium vystaveno. Tento článek představuje experimentální a numerické studie přenosu tepla v písku vystavenému průsakovému toku. Zaměřuje se na vliv nasycené hydraulické vodivosti a pórovitosti média na proces přenosu tepla. Distribuce teploty v písku byla monitorována snímačem distribuované teploty z optického vlákna (DTS). Experiment byl proveden na třech typech písků s převahou oxidu křemičitého s různými nasycenými hydraulickými vodivostmi a odlišnou charakteristickou křivkou půdy (SWCC). Kromě experimentální studie byl v softwaru FEFLOW navržen spojený hydrotermální numerický model a ověřen porovnáním jeho výsledků s experimentálními měřeními. Abychom určili vliv pórovitosti a nasycené hydraulické vodivosti na přenos tepla, analyzovali jsme numerické modely pro různé hodnoty pórovitosti a nasycené hydraulické vodivosti. Numerické a experimentální studie ukázaly, že tepelná rychlost je vyšší v písku s vyšší nasycenou hydraulickou vodivostí a pokles teploty nastává rychleji v důsledku procesu tepelné konvekce. Nasycený písek s větší pórovitostí má celkově vyšší tepelnou kapacitu, proto pokles teploty začal v měřicích bodech později, ale klesl dolů níže blízko teploty vody proti proudu.

The paper presents the design and static analysis of a high arch dam. A feasibility study was conducted on the dam in the 90s and a preliminary layout was designed. However, the dam’s construction phase has been never started. In this paper, the design and layout of the dam under consideration are in accordance with the US manuals for the design of arch dams. The structure’s three-dimensional model was entered into the program SAP2000 and three-dimensional solid finite elements were used to discretize the model. This paper considers the hydrostatic pressure of the water reservoir and concrete self-weight. The analysis was performed for both the maximum and the minimum designed water level and for the case when the reservoir is empty. Special attention is given to the boundary conditions of the dam at its abutments and foundation. The results show that the planned layout is good for the dam’s construction. The arch dam’s curve transfers the loads to the abutments. The significant role of the foundation rigidity and the reservoir water level in the stress distribution and nodal displacements within the arch dam is observed.

Seepage flow through embankment dams and their sub-base is a crucial safety concern that can initiate internal erosion of the structure. The thermometric method of seepage monitoring employs the study of heat transfer characteristics in the soils, as the temperature distribution in earth-filled structures can be influenced by the presence of seepage. Thus, continuous temperature measurements can allow detection of seepage flows. With the recent advances in optical fiber temperature sensor technology, accurate and fast temperature measurements, with relatively high spatial resolution, have been made possible using optical fiber distributed temperature sensors (DTSs). As with any sensor system, to obtain a precise temperature, the DTS measurements need to be calibrated. DTS systems automatically calibrate the measurements using an internal thermometer and reference section. Additionally, manual calibration techniques have been developed which are discussed in this paper. The temperature data do not provide any direct information about the seepage, and this requires further processing and analysis. Several methods have been developed to interpret the temperature data for the localization of the seepage and in some cases to estimate the seepage quantity. An efficient DTS application in seepage monitoring strongly depends on the following factors: installation approach, calibration technique, along with temperature data interpretation and post-processing. This paper reviews the different techniques for calibration of DTS measurements as well as the methods of interpretation of the temperature data. Tento článek shrnuje různé techniky pro kalibraci měření DTS

Various models were developed in the past to simulate different hydrological processes. However, discrepancies between simulated and observed values are still significant and pose a challenge to many researchers. Models contain many parameters that cannot be directly measured. The values of most of these parameters are determined in the calibration process conditioning the efficiency of such models. This paper introduces the use of the enhanced Gauss&ndash, Levenberg&ndash, Marquardt (GLM) procedure in combination with the singular value decomposition (SVD) and Tikhonov regularization to improve the process of hydrological model calibration. The procedure is tested on a freely available hydrological model using a synthetic dataset. Based on several efficiency measures, the GLM procedure, in combination with SVD and Tikhonov regularization, was found to provide efficient model history matching and almost perfect parameter calibration. Moreover, by comparing the results of the proposed procedure with the results of global evolutionary calibration procedures, it was found that the only calibration using the combined GLM procedure gave a perfect fit in low flows. Last but not least, the noise in the calculation results with the combined GLM method was practically the same in either the calibration or validation procedure, suggesting that only computational noise remained in the results.

Seepage is the key factor in the safety of dikes and earthfill dams. It is crucial to identify and localize the seepage excesses at the early stages before it initiates the internal erosion process in the structure. A proper seepage monitoring system should ensure a continuous and wide area seepage measurement. Here, continuous monitoring of seepage at the laboratoryscale is achieved by a passive optical fiber Distributed Temperature Sensing (DTS) system. An experimental model was designed which consists of initially unsaturated sand model, water supply, seepage outflow, optical fiber DTS system, and water and air temperature measurement. Initially, the sand temperature was higher than the temperature of the seepage water. An optical fiber DTS system was employed with a hightemperature resolution, short sampling intervals and short time intervals for temperature monitoring in the sand model. In the system, the small variation in the temperature due to groundwater flow was detected. The numerical analysis was conducted for both the seepage process and the heat transfer progression in the sand model. The results of the heat flow simulation were evaluated and compared with the measured temperature by the optical fiber DTS. Obvious temperature reduction was obtained due to seepage propagation in the sand. The rate of temperature reduction was observed to be dependent on the seepage flow velocity. Proudění je klíčovým faktorem bezpečnosti hráze a přehradních nádrží. Je velmi důležité identifikovat a lokalizovat excesy prosakování v raných stádiích před tím, než zahájí proces vnitřní eroze. Řádný systém monitorování prosakování by měl zajistit nepřetržité měření prosakování - v laboratorním měřítku pomocí pasivního optického vlákna distribuovaného snímání teploty (DTS). Experimentální model byl sestaven z původně nenasyceného pískového modelu, přívodu vody, odtoku, systém optických vláken DTS a měření teploty vody a vzduchu. Zpočátku byla teplota písku vyšší, než teplota protékající vody. Systém optických vláken DTS byl použit s vysokým teplotním rozlišením, krátkými intervaly odběru vzorků a krátkým časem intervalů pro sledování teploty v pískovém modelu. Numerická analýza byla provedena pro jak prosakovací proces, tak i postup přenosu tepla v pískovém modelu. Výsledky simulace tepelného toku byly vyhodnoceny a porovnány s naměřenou teplotou pomocí optického vlákna DTS. Zřejmé snížení teploty bylo dosaženo díky prosakování v písku. Bylo pozorováno, že rychlost snižování teploty je závislá na rychlosti prosakovacího proudu.

This paper presents the first application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Brežice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identified if significant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.