Underground Dam Research Articles

The use of inverse geotherms for determining underground water flow at the Ombla karst spring near Dubrovnik, Croatia

At the site of the Ombla permanent karst spring, near Dubrovnik, Croatia, it is planned that an underground hydroelectric power plant with an installed capacity of 60 MW be built. This assumed power capacity is based on the results of measurements of average annual discharge of the spring, which is approximately 24 m 3 s −1. The positions and dimensions of all the basic structural elements of this power plant have now, after 20 years of interrupted investigations, been outlined. However, one very important problem remained unsolved, concerning the degree of impenetrability of the planned underground dam and especially of its lower part, which is located inside the rock massif below sea level. One of the main results of the extensive hydrogeological and geophysical investigations, including drilling works, was the finding that all karst water discharging into the Ombla definitely flows by means of siphons passing through a roughly semi-circular vertical plane defined by the vertical boreholes drilled into the massif from the investigation gallery, some of which reached the impermeable barrier of the flysch base-rock lying some hundreds of metres below. The length of this plane is somewhat greater than 1000 m. The results of the first temperature loggings in the boreholes drilled from the investigation gallery disclosed a rare natural phenomenon: inverse geotherms, i.e., geotherms with negative geothermal gradients. This phenomenon has been observed at those underground locations and depths where the temperature of the rock or the fluid has a lower temperature than that of the surrounding rock at the same depth. When such a location is encountered, the temperature begins to fall with increasing depth. In the case of the investigated site, the special tectonic, hydrogeological and hydrogeothermal conditions needed for the occurrence of negative geotherms are fulfilled. On the basis of the large number of boreholes which have been drilled in the direct vicinity of the site, and the observed inverse geotherms, it has been possible to estimate the position of the underground karst channels beneath the investigation gallery of the planned dam.

THREE DIMENSIONAL SATURATED-UNSATURATED SEEPAGE ANALYSIS OF UNDERGROUND DAM

This paper desribes the method and result of three dimensional saturated-unsaturated seepage analysis of groundwater flow in an underground dam. Finite element method based on Richards equation is used, and its result for one dimensional infiltration is compared with Philip's analytic solution. Analysis of a model underground dam is carried out to obtain groundwater level distribution in the horizontal plane, moisture content and seepage velocity distributions in the vertical plane. The effectiveness of notching of the dam body as measures to prevent exceeding groundwater rise is discussed. The proposed method of analysis is also applied to an actual underground dam in Miyako island.

In situ flow testing of a cement borehole seal in welded tuff

Waste isolation at the Yucca Mountain repository site may require that penetration (boreholes, shafts, etc.) of the geological barrier be sealed to retard the migration of radionuclides to the accessible environment [1,2]. Cement is being considered as a part of multicomponent seals or plugs for the repository due to its relatively low permeability, high strength, longevity, and swelling capacity [3]. Cement or concrete has long been used as a hydrological barrier in underground mines [4] and in the oil and gas industry [5]. However, insufficient test data exists about the hydraulic performance of cement plugs under in-situ conditions. The primary objective of the present research is to determine experimentally the hydraulic conductivities of cement borehole plugs in welded tufts as affected by field installation and in-situ environment. The test results provide a data basis on the hydraulic behavior of cement seals in rock openings, which are applicable not only to the Yucca Mountain repository site, but also to other engineering practices, e.g. underground dams for seepage or flood control, sealing of abandoned oil or gas wells, and isolation of aquifers from contaminated groundwater. The present paper describes test methods, results and data analysis for the in-situ flow testing. The field results are compared with the results obtained from related experiments conducted in the laboratory.

THREE DIMENSIONAL ANALYSIS FOR FRESH-SALT GROUNDWATER FLOWS AROUND UNDERGROUND DAM BY INTEGRAL EQUATION METHOD

THREE DIMENSIONAL ANALYSIS FOR FRESH-SALT GROUNDWATER FLOWS AROUND UNDERGROUND DAM BY INTEGRAL EQUATION METHOD

Three Dimensional Analysis for Groundwater Flows in Unconfined Aquifer by Boundary Integral Equation Method

Three dimensional computation process by the Boundary Integral Equation Method has been developed for flows in an unconfined aquifer. An availability of the computation process presented here was applied to a duct flow and two dimensional groundwater flow through a dam, and was confirmed by the comparison of the theoretical values with computed ones concerning the potential, flux and groundwater surface profile. Finally, a transient three dimensional flow pattern arround an underground dam was shown as a typical computation example

Groundwater control by Tsunegami underground dam : Kamon, M; Aoki, K Proc Ninth European Conference on Soil Mechanics and Foundation Engineering, Groundwater Effects in Geotechnical Engineering, Dublin, 31 Aug–3 Sept 1987V1, P175–178. Publ Rotterdam: A A Balkema, 1987

Groundwater control by Tsunegami underground dam : Kamon, M; Aoki, K Proc Ninth European Conference on Soil Mechanics and Foundation Engineering, Groundwater Effects in Geotechnical Engineering, Dublin, 31 Aug–3 Sept 1987V1, P175–178. Publ Rotterdam: A A Balkema, 1987

IDENTIFICATION OF PARAMETERS IN INHOMOGENEOUS AQUIFER

In this paper, the method to identify the values of transmissivity and storage coefficient and those distribution in inhomogeneous aquifer is investigated in inverse problem. Especially, the importance of the selecting technique of observed head is emphasized, and the reasonable phases for observing is clearly shown with the sensitivity matrix. The applications of the proposed method to the simple aquifer model and to the area of the underground dam constructed are examined. Numerical values obtained agree well with the observed results in the field.

Design of underground artificial dams for mine water storage

The paper describes the approaches used for design of underground dams in different countries. The merits and demerits of design methods are critically discussed. An approach based on thick plate theory developed by the authors is presented. The factors which govern the thickness of a dam are outlined. The influence of blasting on dam design and a method to estimate the dynamic stresses due to blasting is suggested. In the authors' view only arch shaped dams of cement concrete should be constructed. If the thickness of a dam exceeds 3 or 4 m a multistage dam is suggested. A case study and design details are included in the paper for guidance.

Government-operated Irrigation Project with Underground Dams in Miyako-jima Island, Okinawa, Japan

Government-operated Irrigation Project with Underground Dams in Miyako-jima Island, Okinawa, Japan