Measuring and testing – Borehole or drilling – Downhole test
Patent
1991-11-27
1993-10-19
Williams, Hezron E.
Measuring and testing
Borehole or drilling
Downhole test
73151, E21B 4700
Patent
active
052535193
DESCRIPTION:
BRIEF SUMMARY
The present invention has for its object methods and devices for in-situ measurement of ground heave characteristics.
The technical sector of the invention is the manufacture of material and equipment for carrying out mechanical tests and measurements of ground in-situ.
One of the principal applications of the invention is the determination of ground heave prior to construction of a work thereon.
In fact, numerous works, dwelling houses of low height or industrial implantations, have suffered damage due to expansive ground and especially to heaving ground.
In France, several cases of ground-heave disorders have been noted in the Paris region by Mr. PHILIPPONNAT. Other examples are cited in Rumania (Mr. POPESCU), in Senegal (Mr. THUREAU) or in the United States (Mr. CHEN) for example. It may be noted that these disorders are all raised in clayey soils in arid or semi-arid climates, i.e. in a non-saturated environment.
These expansive clayey soils provoke serious problems for constructions, all the more so as the latter are light. Moreover, such disorders are amplified with time, very slowly, as the works progressively lose rigidity. The most current disorders due to heaving soils are differential deformations, as well as cracks which open and close at the rhythm of the seasons and therefore of the retraction-heaving cycle of the clayey soil.
Certain constructions are sometimes ruined by disorders of this type. The parts most exposed to the action of the heaving ground are the foundations and numerous constructional arrangements are recommended with a view to protecting them, but without optimalization due to lack of measurement and knowledge of the value and of the risk run, which is expensive when it is desired to be sure of avoiding any risk.
In particular, the following may be used: ground.
These preventive arrangements which are expensive due to lack of optimalization are in that case rathermore often ignored.
It therefore appears necessary to prevent heaving of the foundation ground and therefore to be capable of determining, by a test either in-situ or in laboratory, the propensity for future heaving of the clay constituting the ground. The reaction mechanisms of grounds are in fact very complex and are linked with their internal structures, however, which are often very heterogeneous and non-repetitive. The grounds may be classified by internal structures into categories, but the characteristics thereof cannot be quantified without the tests. Therefore, numerous publications, measurements and studies have been made and are being made on each parameter concerned by the problems of heaving with which we are preoccupied, such as, for non-saturated ground, the suction in the soils, the hydrodynamic behaviour and the flow of the water, the effective stress, and the resistance to shear.
Various apparatus have been developed to effect measurements of these parameters, knowing that, for a given parameter, there exists a range of equipment, often a function of the range of value to be measured.
However, it has proved that the principal information concerning the study of non-saturated ground is that of the values of its suction, and there exists a correlation between the drop thereof and the increase in heave, which correlation is one of the keys of the perception of the mechanisms and parameters of the heave.
This aptitude of ground to heaving is at the present time studied only in the laboratory on the basis of so-called "oedometric" tests on samples.
The most conventional method, to within some variants, remains that recommended by PAREZ and BACHELIER which, by a servo-controlled counterweight, prevents the sample from heaving and makes it possible without difficulty to determine the value, after stabilization, of the pressure exerted, which is the heaving pressure.
In fact, the heaving pressure of a ground may be defined either: to occur therein during saturation thereof; saturation to its initial volume before saturation.
The first of these two definitions is the most conventional and remains the one emp
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LeBlanc et al., "Numerical Surface Control Device for In-Situ Ground and Rock Tests with a Deep Drill", a translation of French patent application number 2512860.
Flavigny Etienne
Muschotti Ernest
Dombroske George
Societe Anonyme Stiled E.R.G.
Williams Hezron E.
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