Lugeon Value Research Articles

孔内静水圧試験法（多段階孔内定水位試験法）を用いたルジオンテストの適用性について

The Lugeon test is a kind of water pressure test of the permeability test introduced by M. Lugeon for measuring permeability of the good foundation rocks of dams. Strictly speaking, it is distinguished from the ordinary permeability test, because it is not always based on Darcy's law. However, Lugeon test is extensively used as the permeability test for the foundation rocks of dams.In recent years, dams have been constructed not only on the hard bedrocks but also on the weak rocks, cracky rocks with wide open cracks, etc. Therefore, corrections and adjustments have been applied in testing procedures and interpretation methods.However, in case of bedrocks both with small critical injection pressure and under the condition of deep groundwater level, the proper Lugeon value within critical injection pressure cannot be easily obtained and larger Lugeon value is often gained, for hydrostatic head exceeds the bedrocks' own critical injection pressure and hydrofracturing occurs.In order to refrain from its phenomenon, injection pressure should be provided near the test stage, not on the ground. Therefore, lately improved Lugeon test method using the borehole multistage constant permeability test method have developed. As a result, the above mentioned problems were almost resolved.While, in case of huge permeable bedrocks with wide open cracks, Lugeon value resulted from the ordinary Lugeon test is often considerably smaller, because of huge pipelines friction due to turbulent flow. However, according to the writer's experiences, Lugeon value nearly equal to the real permeability under a laminar flow can be obtained by means of the above mentioned method.

PREDICTION OF GROUT TAKE IN DAM FOUNDATION GROUTING

Although foundation grouting for dams is always performed as one of the most important foundation treatment works, the prediction of necessary cement takes is considered to be difficult. In this paper, several dam grouting projects of granitic rock foundations which have similar specifications have been reviewed, and the results indicate that there exists good correlations between Lugeon value and unit cement takes in grouting procedure.In field practice, Lugeon value is obtained by using the water pressure tests prior to the grout injection, and the value is used for determining the details of further grouting works. The value suggests the properties of rock foundations, but it has been considered to be irrespective of cement grout takes. The study of this paper concludes however, that total amount of grout takes can be predicted from the initial Lugeon value macroscopically.

高粘性流体を用いた岩盤透水係数の測定 熔結凝灰岩を対象としたルジオンテスト

Although the Lugeon test is widely used to measure the permeabilities of rock masses, this test has some problems to be solved. One of the largest problems is how to reduce the influence of the turbulent flow created near the bore hole. The turbulent flow may greatly reduce the measured permeability if the permeability of rock mass is large.A possible technique to reduce the influence of the flow is to inject a highly viscous liquid instead of water. In this study, we tried to measure the permeability by using a highly viscous liquid at a damsite in the Oita prefecture. This area is mainly composed of fractured welded tuff. It was found that the high viscosity liquid was necessary for the measurement of the permeability in this area because the turbulent flow considerably decreased the measured permeability. A relation between the kinematic viscosity of the liquid used, injection pressure, and the Lugeon value obtained when using water was formulated. As a conclusion, the Lugeon test with a high viscosity liquid is a reliable method for the measurement of rock mass permeability.The fracture geometries developed near bore holes were also examined by using a bore hole TV.

PERMEABILITY AND LUGEON VALUES OF DAM FOUNDATIONS

In surveying the permeability of dam foundations, Lugeon water test is usually adopted and the permeability is evaluated by Lugeon value (Lu). The curve between pressure and rate of water injection (p-q curve) is drawn by using the test results and Lugeon value is obtained from the slope of straight line part of p-q curve. However, quite a few p-q curves which have various shapes except the straight line, are obtained when Lugeon water tests are performed at fields. Therefore, in order to interpret the results of Lugeon water tests accurately the authors performs the following things: (1) p-q curves obtained from Lugeon water tests are classified into several categories, (2) causes of several p-q curves classified in (1) are summarized, (3) the methods to determine the accurate Lugeon value from each p-q curve are illustrated.

地すべりにおけるすべり面の起源

Many landslides occur in stratified rock mass; a few landslide, in massive rock mass. In order to explain the phenomena, the joint system in the two geological area is examined on the basis of permeability (Lugeon value) and boring core observation. This reveals that deeper joints are more widely spaced and joints extend much deeper in the stratified rock mass. It is considered, therefore, that the joints are formed under stress relief field and develop remarkably in the stratified rock mass with different elasticity layers.A prerequisite for the occurence of a landslide is the existence of a permeable discontinuous fracture dipping toward a valley. Landslides in stratified rock mass move in general, along the stress relief joints. Even in massive rock mass, many landslides occur in peculiar geology, in which remarkable swelling is founded during tunnel excavation. Consequently, slip surfaces of landslides are regarded to originate mostly in joints, due to expansion of either stratified or massive rock mass.

Routine interpretation of the lugeon water-test : Houlsby, A C Q J Engng Geol, V9, N4, 1976, P303–313

Summary A relatively simple routine method of calculating and interpreting the “modified” Lugeon water test is described. The method is used for assessing the need for foundation grouting at dam sites; it comprises calculations of lugeon values for each of five test runs at increasing and then decreasing pressures, followed by interpretation of the pattern of results, and hence selection of an appropriate representative permeability. The relative frequency of different behaviour patterns is indicated by reference to 811 actual tests.

Routine interpretation of the Lugeon water-test

Summary A relatively simple routine method of calculating and interpreting the “modified” Lugeon water test is described. The method is used for assessing the need for foundation grouting at dam sites; it comprises calculations of lugeon values for each of five test runs at increasing and then decreasing pressures, followed by interpretation of the pattern of results, and hence selection of an appropriate representative permeability. The relative frequency of different behaviour patterns is indicated by reference to 811 actual tests.