Lugeon Test Research Articles

A STUDY ON THE ANALYSIS OF GROUND WITH DOUBLE POROSITY MODEL

An idealized double porosity model is developed for the purpose of studying the coupled effects of flow in porous blocks and fractures as well as solid displacement in saturated-unsaturated medium.Subsequently, Galerkin formulation is used for the finite element method to develop a new technique to investigate coupled hydraulic-mechanical behavior in the double porosity model reservoir.The verifications are performed in comparison with an analytical solution of one-dimensional consolidation problem and experimental results of unsteady flow in the sand box. Finally, a secondary compression is examined with this model, the environment of rock mass in Lugeon test is simulated, and two-dimensional consolidation problems in a saturated and saturated-unsaturated media are investigated with comparison with the single porosity model.

回転探触子型岩盤割れ目検知計による現場試験 (続報)

A crack-detector has been developed for measuring the -distribution of open cracks and the change sonic velocity in rockmasses, and in-site measurements have been performed with it. This paper describes the in-site measurements at three site.The results obtained in this study are as follows;1) At I tunnel, the distribution of cracks and the sonic velocity in a borehole were measured by the crack-detector. Thedistribution of cracks at the inner surface of the same borehole was observed with a borehole television camera. Theresults of undetectable area by the crack-detector were found in good agreement with open cracks obtained by theborehole television camera.2) At H quarry, Lugeon's tests and the measurements by the crack-detector were done in a borehole before and afterthe grouting to estimate the effect of the grouting operation. From the Lugeon's tests, the grouting operation hadlittle effect on filling the cracks. On the other hand, the position of the imcomplete filling-open crack was found withthe crack-detector.3) In order to comfirm what part of a retaining wall was damaged by an earthquake, the distribution of open cracks andthe change of sonic velocity were measured by the crack-detector in a borehole drilled in the retaining wall. From theresults of measurement, it was clear that the crack zone in the retaining wall lies on the extension of the boundarybetween the natural ground and the banking.These findings show that the use of the crack-detector is practical when the distribution of open cracks correspounds tothe undetectable area of the measurements for the design and maintenance of rock and concrete structures.

Water in Site Investigation

Abstract It is water that makes the difference between a dried-out clay as hard as a brick, and mud. The dry fields of summer can become a quagmire for construction work. Examples are given of rapid deterioration of chalk when allowance had not been made for the effect of a known high water table when excavation went below it and the effect of water on loose backfill at an opencast site. Houses had been built before the water level rose in the old pit and were damaged by the resulting settlements. Soil fabric can make the overall field permeability much greater than that obtained from tests on small samples and completely upset predictions of quantities of water and number of wells required for ground water lowering. Out of balance water pressures caused by allowing the water level in a borehole to be much below the ground water level can lead to low SPT N values and disturbed samples. The result could be unnecessary expense on the new works. False results may be obtained if excessive pressures are used in making field permeability tests such as the Lugeon test. On the other hand, hydraulic fracture tests can be used to obtain an assessment of total stress conditions in the ground.

Discussion Session 7

J.S. Sutton (Sir Alexander Gibb & Pts) queried Dr Money's dismissal of the Lugeon test in which although only a limited volume of rock in the immediate vicinity of the test length is tested, the conditions are comparable to those developed in curtain grouting. Hence the test results are usually comparable with grout take and illustrate the more general principle that the applicability of any test is greatest when its scale is closest to the scale of the engineering problem being analysed. Often external constraints preclude the use of appropriately scaled tests and it is perhaps a major justification for the use of specialist engineering geologists to relate small scale test results to actual conditions.

Rock grouting and water testing at Kielder Dam, Northumberland

Summary A cement grout curtain has been formed in the North Abutment bedrock of Kielder Dam in Northumberland. In order to gauge the effectiveness of the grouting, a series of pre- and post-grouting Lugeon water tests were conducted in special control holes. This programme was executed according to proposals made in this journal on Lugeon testing ( Houlsby 1976 ), which have now gained world-wide acclaim and acceptance. The paper demonstrates clearly both the practicality of the method and the usefulness of the results. Safe grouting pressures were selected following hydrofracture tests, again using similar methods. Data on curtain grouting design, execution and analysis are also provided, and fundamental observations made on the relationship of water takes and cement grout consumptions.

Seepage Control Methods in Dam Foundations and Abutments Consist of Recent Volcanic Rocks in Kyushu

Dams constructed on recent volcanic rocks have many difficult problems on foundations and abutments such as strength, permeability and so on. Authors have been conducting case studies on 25 dams constructed on Neogene and Quaternary volcanic rocks in Kyushu District to find out the most relevant seepage control methods for such dams. Obtained results are as follows.From a seepage control viewpoint, geological features of studied dams are classified into following six large groups: 1) Lava, 2) Alternation of lava and pyroclastic rocks, 3) Tuff breccia, 4) Densely welded tuff, 5) Partially welded tuff-“Shirasu”, 6) Old river deposits etc. On the other hand, permeability of rock mass estimating from ground water level at abutments is classified into following three large groups: A) Ground water level at abutments is relatively high, B) Ground water level at abutments is relatively low but higher than river bed elevation, C) Ground water level at abutments is lower than river bed elevation.Considering these six geological features and three permeability characteristics, the most relevant seepage control methods proposed by authors are shown in Table 7. As shown in Table 7 curtain grouting can be applied for a wide variety of geological conditions. Detailed profile of curtain grouting is shown in Table 8. But both Table 7 and 8 are tentative standards at early planning stage, so practical seepage control methods should be selected taking full account of precise geological conditions of each dams and conducting various in situ tests such as grouting test, Lugeon test, pumping test, etc.As recent volcanic rocks in Kyushu are often distributed laterally, problems on seepage control arise from not only dam sites but also overall storage areas. So it is important to investigate geological conditions of overall storage areas and to point out problems. Then the most relevant seepage control methods should be selected for various geological conditions such as consolidation grouting, limb grouting, branket, concrete cutoff, etc.

ルジオンテスト施工指針（案）について

The seepage through dam foundations and abatments reduces the capacity of storage and, furthermore, might cause the failure of dam. It costs very much to reduce seepage by grouting and other water tight procedures.Lugeon test method is common practice for measuring rock mass permeability in the field of dam construction. However, there was no standard test procedures nor interpretation methods. Therefore, the Ministry of Construction defined tentatively the Manual of Lugeon Test in 1977. Some test procedures are as follows; (a) the borehole diameter should be 66 mm, (b) test section length should be 5m, (c) the maximum pressure at the test section should be over 10kg/cm2 unless ground breaks.

The interpretation of the Lugeon water-test

Introduction The use of water-tests, of gradually increasing elaboration, for establishing the need for, and results of, grouting injections in rock has been discussed frequently (Randall 1923, Fox 1927, Lugeon 1933, Vaughan 1963, Little et. al 1963, Bishop et al. 1963, Fergusson & Lancaster-Jones 1964, Benko 1964, Lancaster-Jones 1967, Snow 1968). By ‘rock’ in this context is meant that part of the Earth's crust in which water circulation is mainly via fractures, joints and other random openings, so that the material cannot be considered as a homogeneous porous medium. Porous sandstones and limestones are included since they also contain joints. Few standard tests have however become accepted; an exception is that named, from it's originator, the Lugeon test. Since first described in 1933 this has been elaborated (Camembert 1964). The problem of extrapolation Although the Lugeon test may serve other purposes, its main object is to determine the ‘Lugeon coefficient’ which by definition is a water absorption measured in litres per metre of test-stage per minute at a pressure of 10 kgs/cm2 (1 MN/m2). At shallow depths or in weak rocks it is not always appropriate to apply such high pressures and the methods used for extrapolating the results of tests at low pressures in order to determine the Lugeon coefficient have been open to question, although Fergusson & Lancaster-Jones ( op. cit ) pointed out that such

Aménagement Caprivari-Cahoeira étude en charge

This article refers to the design studies and work done in constructing the pressure shaft in the Capivari-Cachoeira hydro-power scheme, which has an installed output of 250,000 kW. The shaft operates under pressures of up to 85 kg/cm2. Its diameter is 3.0 m in the upper unlined portion and 2.90 m in the lined portion below it. The article begins with a theoretical study of stresses in indefinite porous ground out of which a cylindrical cavity has been hollowed out and filled with water under a constant pressure. The ground thus contains a flow, the resulting loss of head being simply considered as an additional volume force acting at all points in the ground. The calculation result confirms the Bratz theorem which states that the forces acting at any point are defined simply by adding the percolating flow pressure and the stresses in the ground, assuming pressure to be only applied on the surface. The discrepancies between the resulting conclusion and the results of two other investigations are explained by calculation : the strain assumptions differ in each case, but each has its own particuar field of application. A theoretical study of the effect of grouting on the percolating flow characteristics is then described. Next, the results of pressure tests on a cavity under conditions which are seldom if ever attained in practice are discussed. The cavity was 15 m long, with a diameter of 2.20 m and was subjected to a pressure of 65 kg/cm2. The test was also appllied to the cavity with unlined sides, then with a concrete lining grouted under high pressure. The load with stood by the rock was found to he practically the same in both cases, with little difference between the respective leakage rates. The analysis of losses over a period of time confirmed the results of a theoretical interpretation of these effects, it having been found that the filling of the ground with water appeared to reduce the losses, i.e. an effect which is generally ignored in standard tests on small-diameter wells. These tests were completed by tests in which small-diameter boreholes were put under pressures of up to as much as 100 kg/cm2 by the classical Lugeon test method. The results obtained are compared with the experimental cavity data. This enabled the upper limit of the lined shaft portion to be determined, which was found to be at a point at which the maximum static head was 400 m of water. Finally, the calculations whereby the lining thickness in the lower shaft portions were determined are discussed. These calculations as conventiona1 as regards internal pressures, but an original solution was found to the outside pressure problem which consisted in sinking a shaft running parallel to the lined shaft and providing drainage borings to eliminate dangerous water pressure in the ground when emptying the system.