US3690389A

US3690389A - Method and an apparatus for taking an undisturbed soil sample

Info

Publication number: US3690389A
Application number: US7789A
Authority: US
Inventors: Roelof Van De Beld; Heinrich K S P Begemann; Hendrikus J Bos; Adriaan B Mann
Original assignee: ADRIAAN B MANN; HEINRICH K S P BEGEMANN; HENDRIKUS J BOS
Current assignee: ADRIAAN B MANN; HEINRICH K S P BEGEMANN; HENDRIKUS J BOS
Priority date: 1969-02-07
Filing date: 1970-02-02
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: JPS5025403B1; NL6902019A; NL165553B; FR2032810A5; DE2005539A1; BE745576A; DE2005539C3; GB1304701A; NL165553C; DE2005539B2

Abstract

A method and an apparatus for taking an undisturbed soil sample are described, by means of which the soil sample, which, during the introduction of a sampling tube into the soil, is surrounded by a hose, is supported substantially over its full length by means of a supporting tube which, after removing the sampling tube from the soil, is also used for transporting the sample to a laboratory. This supporting tube may consist of separate tube selections connected together by adhesive tape, so that the sample may be divided in easily transportable sections by cutting the adhesive tape and the sample. For facilitating the penetration of the sample into the sampling tube, a lubricating liquid may be used, and the sample may be supported near the lower end of the sampling tube by means of a supporting liquid, both liquids being immiscible. The lower part of the sampling tube is provided with means for pinching off the sample, and the corresponding secton of the supporting tube is weakened so that it may be deformed correspondingly, said pinching means being provided with means for locking it in its extreme positions, and with means for transferring pressing and pulling forces. Means are provided for closing the upper end of the hose and for guiding this end coaxially with the supporting tube for allowing the lubricating liquid to be uniformly distributed around the hose.

Description

United States Patent Van De Beld et al.

1451 Sept. 12,1972

[54] METHOD AND AN APPARATUS FOR TAKING AN UNDISTURBED SOIL SAMPLE [72] Inventors: Roelof van de Beld; Heinrich K.S.P.

Begemann; Hendrikus J. Bos; Adriaan B. Mann, all of Laboratorium voor Grondmechanica, Stieltjesweg 2, Delft, Netherlands [22] Filed: Feb. 2, 1970 [2i] Appl. No.: 7,789

[30] Foreign Application Priority Data Feb. 7, 1969 Netherlands ..69020l9 [52] US. Cl. ..l7S/59, 175/245, 175/249 [51] Int. Cl. ..E2lb 9/20, E2lb 25/00, E2lb 49/02 [58] Field of Search....l75/59, 60, 58, 245, 246, 249,

Primary Examiner-Stephen J, Novosad AuomeyMarmorek & Bierman [5 7] ABSTRACT A method and an apparatus for taking an undisturbed soil sample are described, by means of which the soil sample, which, during the introduction of a sampling tube into the soil, is surrounded by a hose, is supported substantially over its full length by means of a supporting tube which, after removing the sampling tube from the soil, is also used for transporting the sample to a laboratory. This supporting tube may consist of separate tube selections connected together by adhesive tape, so that the sample may be divided in easily transportable sections by cutting the adhesive tape and the sample. For facilitating the penetration of the sample into the sampling tube, a lubricating liquid may be used, and the sample may be supported near the lower end of the sampling tube by means of a supporting liquid, both liquids being immiscible. The lower part of the sampling tube is provided with means for pinching off the sample, and the corresponding secton of the supporting tube is weakened so that it may be deformed correspondingly, said pinching means being provided with means for locking it in its extreme positions, and with means for transferring pressing and pulling forces. Means are provided for closing the upper end of the hose and for guiding this end coaxially with the supporting tube for allowing the lubricating liquid to be uniformly distributed around the hose.

29 Claims, 7 Drawing Figures PKTENTED 1972 i 3,690,389

SHEET 1 OF 3 INVENTORQ- 4404M mu BY flMJ- ATTORNEYS.

PATENTEBSEP 12 I972 SHEET 3 0F 3 INVENTORS: vM a 2M4,

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BY Alhq'mm WM )Zw M ATTORNEYI METHOD AND AN APPARATUS FOR TAKING AN UNDISTURBED SOIL SAMPLE This invention relates to a method and an apparatus for taking an undisturbed soil sample, which apparatus comprises a cutting tube having a sharp cutting mouth, an annular chamber being disposed roundthe bottom end of the tube, in which chamber transversely resiliently stretchable hose may be arranged, which may enter into the interior of the sampling tube through a slot near the cutting mouth and may be carried along with the penetrating sample, as a result of which this sample is completely enclosed by the hose. Furthermore a supporting liquid may be used which may penetrate into this chamber at least in the vicinity of the slot, for keeping the hose free of the slot and for transversely supporting the sample at least near this slot.

Such a method and such an apparatus are described in the Dutch Patent No. 125 036 and US. Patent No. 3,511,324. The latter Patent describes a hose provided with a liquidproof coating, in order to prevent that the supporting liquid penetrates into the sample and that the water present in the sample runs out. The supportin g liquid fills the small space between the hose and the inner wall of the cutting tube and the extension tubes fixed thereto, as a result of which, on the one hand, the

friction between the hose and the tube is eliminated,

and, on the other hand, a lateral support of the sample is obtained by the static pressure of the liquid, which lateral support is supplemented by the supporting force which is a result of the fact that the lateral deformation of the hose is considerably reduced by the pulling force exerted thereon in axial direction.

For obtaining an undisturbed drilling profile the latter method has been satisfactory. However, in certain laboratory tests, an undisturbedness of the sample should be aimed at which cannot be achieved by the latter method. The support obtainable in this method may be insufficient in such cases, since it is possible that the sample is either outwardly deformed, at least locally, or is compressed by an excessive supporting pressure. In addition it is difficult to transfer the sample from the cutting tube into tubes suitable for the transport to the laboratory without additional deformation.

It is an object of the invention to improve these known methods and apparatus such that these disadvantages are eliminated.

For that purpose the method of I the invention is characterized in that a coaxial supporting tube is introduced into the cutting tube, which coaxial supporting tube extends up to the vicinity of the slot of the hose chamber and has an inner diameter which is only very little larger than the outer diameter of the sample surrounded by the hose, a lubricating liquid being introduced at the upper side of said supporting tube in order to fill the space between the hose and the supporting tube. Moreover, if necessary, a supporting liquid may be introduced into the interspace between the supporting tube and the cutting tube communicating with the hose chamber.

The surface tension and the viscosity of the lubricating liquid and the width of the interspace between the supporting tube and the sample are chosen in such a manner that, as the sample enters the supporting tube, the lubricating liquid remains in said interspace, but a transverse inward deformation of the sample in consequence of the static pressure of said liquid or the expulsion of the liquid layer by the outward pressure of the sample are avoided.

In particular the lubricating liquid has a greater cohesion to the wall of the supporting tube than to the wall of the hose, and, furthermore, the lubricating and supporting liquids may be mutually repellant in order to prevent the supporting liquid from being carried along into the space between the supporting tube and the sample.

By means of this method an unambiguous support of the sample is ensured over its total length and independent of its composition, and, moreover, friction between the hose and the supporting tube is eliminated.

Preferably the supporting tube comprises individual tube sections,.the length, of which corresponds to that of the cutting tube proper or to its extensions, said tube sections being placed together with their terminal faces against each other and being connected to each other in a sealed manner by means of an adhesive tape strip,

and, after withdrawal of the cutting tube from the soil, the individual tube sections together with the sample portions present therein are separated from each other by cutting the adhesive tape strip, the hoseand the sample, and covering the cutting planes with a covering for transporting the sample portions to the laboratory,

so that the disturbance of the sample when being transferred to transport tubes, such as required in the usual methods, is avoided.

In order to ensure a uniform penetration of the lubricating liquid into the interspace between the sample and the supporting tube, and, especially, to prevent the hose and the supporting tube wall from locally contacting one another, an exactly axial guiding force may be exerted on the closed upper end of the hose.

The apparatus of the invention for carrying out this method is characterized by a separate rigid supporting tube which sealingly fits into a fitting provided in the cutting tube proper near the exit slot for the hose and which is coaxially supported in the cutting tube. Particularly the interspace between the cutting tube and the supporting tube near the exit slot for the hose may be connected to the interior of the hose chamber.

In this manner it becomes possible that, as described in the afore-mentioned US. Pat. No. 3,511,324, that the hose will be pressed against the outer wall of the hose chamber near the lower side of the chamber by the supporting liquid present in the hose chamber, the latter being rounded towards the exit slot so that the hose emerges approximately tangentially to the sample, and, at the same time, the sample is supported by the supporting liquid at the locationof said slot and prior to reaching the supporting tube. Since, furthermore, the support of the sample is entirely taken over by the supporting tube, the supporting pressure exerted by the supporting liquid can be completely adapted to the pressure value required near said slot. In the usual apparatus this is not possible since the supporting liquid should serve for the support of the entire sample.

Particularly, the inner tube which defines the hose chamber at the inner side may be provided at the inner side with longitudinal grooves, the intermediate ribs thereof contacting the supporting tube, said grooves communicating, on the one side, with the interspace between the supporting tube and the portion of the supporting tube proper and its extensions above the hose chamber, and, on the other hand, with the lower side of the hose chamber. The passage through these grooves should be sufficiently wide for ensuring sufficiently wide for ensuring sufficient supporting pressure at the lower side of the cutting tube where only the supporting liquid is active.

Particularly this inner tube may be a thin-walled tube abutting'against a cage consisting of longitudinal thin rods which may contact the supporting tube.

At their lower sides these rods may be mounted in a lower fitting ring defining the exit slot for the hose, and their upper sides are mounted in an upper fitting ring defining the upper side of the hose chamber and being provided with recesses between the fixing points of the rods, saidrecesses communicating with the interspace between the cutting tube and the supporting tube above this chamber, and the ring portions between these recesses form guiding and supporting faces for the supporting tube.

Particularly .the upper fitting ring for the rods is secured in the cutting tube by means of a ball joint, and the lower jetting ring is separate from the cutting tube so that, as described in British Pat. No. 1,129,130 the exit slot is prevented from being shut off at a possible bending of the cutting tube.

, Furthermore the lower fitting ring is provided with an inner shoulder forming the fitting for the supporting tube.

The lower. edge of the lower fitting ring is outwardly and downwardly bevelled and forms, together with a ring which is'correspondingly bevelled at its outside and is secured in the cutting mouth portion of the cutting tube, the exit slot for the hose, the latter extending substantially tangentially to the entering sample.

Thisufitting ring may, particularly, end in a thin resilient lip, and the adjacent inner wall of the fitting ring extends substantially parallel to it, so that, when the cutting tube is upset when pressing it into the soil, its slot width is not appreciably reduced.

In most cases the supporting tube consists of separate tube sections, the length of which being about the same as that of the extensions of the cutting tube, which tube sections can be placed together with their terminal faces contacting each other, and the length of the lowermost tube sections fitting into the fitting at the lower end of the cutting tube corresponding to the length of the cutting tubeproper.

Furthermore the apparatus of the invention is provided with a flexible sleeve disposed above the hose chamber, said sleeve being fastened with both ends in a ring, the lower end of which is unrotatably connected to the lower cutting tube portion, and the upper end is coupled to a coupling tube which is rotatable but not slidable with respect to the cutting tube, which coupling tube may be firmly connected to the first extension tube in order to be able to distort said flexible sleeve by rotation of said coupling tube and thereby pinching the sample disposed within said sleeve, said upper ring and coupling tube being provided with locking means for maintaining said torsion sleeve in itw twisted position. Similar parts are known, in respect of which reference is made to the Dutch Pat. No. 125,036 mentioned before. For allowing the sample to be pinched when using a supporting tube, the wall thickness of the lower tube section of the supporting tube which is placed into the cutting tube proper is reduced at the location of this torsion sleeve as from its outside such that the supporting tube can be pinched flat by means of said sleeve.

The coupling between said coupling tube and the lower cutting tube portion comprises two grooves in the outer surface of the the coupling tube, which are symmetrically distributed over the surface and may have a length of arc of for example, which grooves are axially extended at their ends, and the inner wall of the cutting tube is provided with lugs fitting into these grooves, all this in such a manner that in their extreme positions the coupling tube and the cutting tube are non-rotatably coupled to each other, but are axially movable with respect to one another so that, in one extreme position, when this tube is withdrawn, transverse stopping faces of the coupling tube and the cutting tube proper contact each other for transmitting the axially directed compressive and pulling forces respectively. The locking is released by moving the extension tubes axially in opposite senses, whereafter the other extreme position can be reached by rotation. Thus, at the end of the pressing action, the coupling tube is brought in its pulling position, in which, during rotation, the uppermost ring which is coupled to this tube is carried along so that the torsion sleeve is twisted and is kept in the twisted position during pulling.

In large diameter samples an accordingly heavy pinching should occur for which purpose a relatively long torsion sleeve is required, which, however, leads to an excessive length of the portion in question of the cutting tube proper which may be weakened thereby. Nevertheless, for being able to use short torsion sleeve, its lower ring may be nonrotatably but axially slidably coupled to the cutting tube by means of a key, thus allowing the torsion sleeve to be shortened corresponding to its twisting as the upper ring is rotated. If desired, the lower ring may be maintained in its lower position by means of a snap lock until, during twisting, a certain pulling force is exceeded.

Preferably the grooves in the cutting tube have such a helical shape that the coupling tube in being rotated is displaced over a distance which is about equal but is opposite to the free travel of the coupling tube between its pressing and pulling positions. In this way a further decrease in length may be obtained.

Furthermore the apparatus of the invention may be provided with a clamp to be fixed to the upper end of the hose and provided with guiding lugs which may bear against the inner wall of the supporting tube, in order to ensure that the upper side of the hose remains as symmetrical as possible with respect to the supporting tube, so that the lubricating liquid may-uniformly penetrate into the interspace between the hose and the supporting tube, the interspace between the lugs being sufficiently large for allowing an undisturbed passage of the lubricating liquid.

Particularly, said clamp comprises a circular disc which may be clamped, with interposition of the free rim of the hose, on a plug disposed within the hose, this plate being provided with guiding lugs. More specifically these lugs may be spaced from said clamping plate by means of substantially axial connecting pieces in order to interfere as little as possible the lubricating liquid from forming a film.

For further decreasing the risk of tilting of the clamp, a pin may be disposed in the center of and perpendicularly to the clamping plate, to which pin the drawing string may be fastened, this pin, near its free end, being provided with a number of guiding lugs bearing against the wall of the supporting tube.

The invention will be explained below with reference to the drawing, in which:

FIG. lshows a longitudinal section of a cutting tube according to the invention provided with cutting mouth, without the protective hose and the supporting tube;

FIG. 2 shows a section on the line Il-II of FIG. 1;

FIG. 3 shows a view, partially in section, of the inner tube of this cutting tube with a supporting tube disposed therein;

FIG. 4 shows a section on the line IV-IV of FIG. 3;

FIG. 5 shows a section through the lower part of the cutting tube with a supporting tube placed therein during the penetration of a soil sample, as well as means for closing and guiding the end of the hose filled with the sample; and

FIGS. 6A and 6B show schematic developments of guiding grooves of a coupling part of the cutting tube. FIG. I shows a cutting tube 1 proper provided at one end, in the usual way, with a cutting mouth 2, which tube may be extended at its other end by means of extension tubes 3. Within the lower portion of this cutting tube an annular hose chamber 4 is closed at its upper side, and ends at its lower end into a slot 6 extending substantially tangent to the inner wall 7 of the cutting mouth 2. The end wall 8 of this chamber is rounded so that the hose present in the chamber 4 can be lead out tangentially to the sample, as shown in FIG. 5. This construction is of current design.

The inner tube 5, however, differs from the usual inner tube. This tube comprises an upper fitting ring 9 provided at its upper end with a more or less spherical thickening 10 which fits into corresponding seat 11 of the outer tube 1 so that the fitting 9 is adjustably held in the outer tube. Furthermore the inner tube 5 comprises a lower fitting ring 12, the bevelled inner wall 13 of which defining the exit slot 6. Both fitting rings are connected to each other by a number of thin rods 14 made of stainless steel or the like. These rods 14 are fixed in lugs 15 which, as shown in FIG. 2, extend into the bore of the fitting ring 9 at the latters lower side, and are separated from each other by recesses 16. In addition a thin-walled tube 17 of stainless steel or the like is disposed round the cage formed by these rods (FIGS. 3 and 4), said tube forming the inner wall of the hose chamber 4. In this way the lower fitting ring 12 is suspended from the adjustable upper fitting ring 9, so that, from the occurrence of minor distortions of tube 1, the slot 6 is kept substantially symmetrically, in order to avoid the risk of the hose being pinched, as described in British Pat. No. 129,130.

Both

fitting rings

9 and 12, together with the cage 14, form a support for a removable supporting tube 18 (FIGS. 3 and 4). This tube 18 has a close fit in a seat 19 of the fitting ring 12. The inner diameter of tube 18 and that of the portion 20 of the fitting ring 12 contiguous to the seat 19 are approximately equal to the inner diameter of the end 7 of the cutting mouth so that, as appears from FIG. 5, the sample surrounded by a hose slidingly fits into the tube 18 and is laterally supported thereby.

The lugs 15 in the upper fitting ring 9 have an interior circular inner wall, the diameter of which corresponds to the outer diameter of the supporting tube 18. Also at its upper end the fitting ring 9 is provided with interior lugs 21, the inner faces of which rest against the tube 18, with passages 22 lying between these lugs. The extension tubes 3 may be provided with such lugs too in order to maintain the supporting tube 18 co-axially and at a small distance from the inner wall of these tubes.

When using such a sampler, the cutting tube 1 is pressed into the soil in the usual way and is provided with extension tubes 3. The'supporting tube 18 comprises individual sections having a length approximately equal to that of the extension tubes. These tube sections are placed together with their terminal faces against each other, and are connected to each other by means of adhesive tape. The lower supporting tube which, as will be described below, slightly differs from the other tube sections, is inserted into the seat 19 of the fitting ring 12 and will, then, be supported by the

lugs

15 and 21, as clearly appears from FIG. 3. A supporting liquid is poured into the interspace between the tube sections 18 and the extension tubes 3, which liquid will flow downwards through the

recesses

22 and 16 through the interspaces between the rods 14. The inner sides of these rods rest against the supporting tube 18 (FIG. 4) and uniformly support this tube against the radial forces exercised by the sample. At its lower end the tube 17 is provided with a number of holes 23 which open into the hose chamber 4. Thus the supporting liquid can penetrate into the hose chamber 4.

As appears from FIG. 5, the supporting liquid will press the hose 24 in the chamber 4 and near the holes 23 outwardly. Since the hose is pleated around the tube 17 in the chamber 4, the supporting liquid cannot penetrate very much into this chamber. However, these pleats are fastened when pulling the hose through the slot 6. The hose is pressed by the supporting liquid against the rounding 8 so that the hose leaves the slot 6 substantially tangentially to the sample 25. The static pressure of the liquid in the complete cutting tube acts upon the exterior of the hose and the slot, so that, during its penetration from the cutting mouth wall 7 to the inner wall of the supporting tube 18, the sample is transversely supported at the location of the mouth of the slot. Since, as will be described below, this supporting liquid needs only be active at the location of the slot 6, its composition may be chosen so that its pressure in that point is just sufficient for supporting the sample against lateral deformation. In the known methods for taking samples with such a hose the supporting liquid has, in addition, to provide for an additional supporting pressure over the full length of the sample, so that, when the samples consist of layers having a considerably different compressibility, there is always the risk of the supporting pressure being locally too high or too low. According to the invention, however, the sample is completely supported by the supporting tube 18 so that this risk is avoided and the support supplied by the supporting liquid may be exclusively adjusted to the slot region.

As a result of the radial pressure of the sample 25, the hose 24 is pressed against the inner wall of the tube 18, thus producing a considerable friction which will induce deformation of the sample. For eliminating this friction a lubricating liquid is injected into the tube 18 having such a viscosity, surface tension and other physical properties that it forms a thin film between the supporting tube 18 and the hose 24. The adhesion of said liquid to the tube 18 should be greater than to the hose 24 in order to prevent the liquid from being carried along as the sample penetrates. The coherence and thickness of the layer should be sufficient for preventing that the layer is pressed away as a result of a local radial pressure, and that the hose contacts the tube wall. On the other hand this layer may not be so thick that the static pressure of the column of liquid will act upon the hose. Finally this lubricating liquid should be immiscible with the supporting liquid used, in order to avoid that the supporting liquid is carried along with the hose.

As usual the supporting liquid may be an aqueous suspension, the specific weight of which is adapted to the soil pressure to be counteracted. The lubricating liquid may be a lubricating oil type of liquid in which if necessary additional substances have been dissolved or suspended for adjusting the specific weight. As a matter of fact many other pairs of liquids may be used meeting the requirements.

For ensuring a uniform lubricating layer to be formed, a care should be taken that the upper side of the hose, which is closed and connected to a string which, during the introduction of the cutting tube into the soil, is kept tensioned for maintaining the upper end of the hose at a fixed height (showing that the sampling properly proceeds), be kept exactly coaxially in order to delimit, with the supporting tube 18, a slot opening which is as uniform as possible. For that purpose a clamp shown in FIG. is used. This clamp substantially comprises a plug 26 and a disc 27. Before the sample cutting is started, the disc 27 is introduced into the inner tube, and then the hose 24 which has been pulled inwards through the slot 6 is folded between the disc 27 and the plug 26, which plug is subsequently connected to the disc 27 by means of a screw connection so that the hose is clamped between the plug and the disc. The disc 27 is provided with a plurality of lugs which are uniformly distributed over the circumference, the outer diameter of which lug assembly being equal to the inner diameter of the tube 18, so that the disc is accurately centered in the tube 18. The diameter of the disc 27 between the lugs 28 is smaller so that the lubricating liquid may enter the interspace 29 between the hose and the tube 18. Preferably the lugs are slightly offset with respect to the plane of the disc 27 as shown in F IG. 5.

As shown the disc 27 is connected to a rod 30 which,

at its free end, is provided with an eye 31 to which the pulling string 32 referred to may be connected. In order to avoid tilting of the clamp assembly which would lead to the slot 29 being closed off, it is advisable to provide a number of radial arms 33 in the vicinity of the eye 31 and the ends of these arms may be provided with lugs abutting against the inner wall of the tube 18.

In withdrawing the cutting tube from the soil, it should be avoided that the sample sags as soon as the soil pressure disappears. For that purpose it is custom ary to pinch off the sample near the cutting mouth. Generally a resilient sleeve is used to that end, one end of which being fixed to the first extension tube, and the other end being coupled to the first extension tube, both tube portions being rotatably connected to each other. When the last extension tube protruding from the soil is rotated, the first extension tube will rotate with respect to the cutting tube proper, in consequence of which said sleeve is twisted and the sample is constricted, so that a support for the sample is provided. Without additional provisions, however, the presence of the supporting tube 18 according to the invention will make it impossible to constrict the sample.

In FIG. 1 such a pinching assembly isshown. At the location of this assembly, the wall thickness of the supporting tube 18 has been reduced, e.g. by turning off the outside of the wall in said region, as indicated at 34. This renders the wall sufficiently yieldable for being constricted when being pinched. Thereby its radial stiffness decreases, but by the presence of the supporting liquid which is also present round the pinching assembly sufficient lateral support is ensured.

In a cutting tube destined for large diameter samples the pinching assembly has to be slightly altered. The assembly shown in FIG. 1 comprises the usual torsion sleeve 35 which is clamped between two

fitting rings

36 and 37. The upper fitting ring abuts against a shoulder 38 of the outer tube 1 and is coupled to a coupling tube 40 by means of one or more teeth 39, which coupling tube rotatably fits in the end of tube 1 and may be connected to the first extension tube 3. This coupling tube 40 is provided with two circumferential grooves 41 each spanning an arc of about lugs 42 provided at the inside of the tube 1 engaging these grooves. The ends 43 and 44 are axially extended and thus form locking seats for the lugs 42 as shown in FIG. 6.

When the tubes are pressed down, each lug 42 is in the corresponding seat 43. In this position the sleeve 35 is untensioned, and the end face 45 of the coupling tube 40 may contact the fitting ring 37 as a consequenceof the axial extrusion of the end 43 of the groove, so that the pressing force exerted by the extension tubes on the coupling tube may be transmitted to the outer tube 1 via the shoulder 38. This situation is schematically shown in FIG. 6A in continuous lines. In this situation the lugs 42 are secured against rotation in the groove ends 43.

When the cutting tube has to be withdrawn from the soil, a pulling force is exerted on the extension tubes causing the lugs 42 to be released from the groove ends 43. Thereafter the extension tubes are rotated, so that each lug 42 passes through the corresponding groove 41 until the other end 44 is reached. When, subsequently, the extension tubes are pulled again, the lugs 42 will snap into the axial extensions 44 of the grooves 41. This causes a shoulder face 46 opposed from the end face 45 to contact a shoulder 47 of the outer tube 1, so that the pulling force exerted on the coupling tube 40 is transmitted in turn to the outer tube 1.

During rotation of the coupling tube 40 with respect to the outer tube 1, the fitting ring 37 is engaged by the teeth 39. Theother fitting ring 36 is not rotatable with respect to the outer tube 1 so that the torsion sleeve 35 disposed between both rings is twisted. In reaching its final position the coupling tube 40 is secured in the groove ends 44 by the lugs 42, so that the torsion sleeve 35 is held in its twisted position.

When the sample has a large diameter, the torsion sleeve should be submitted to a considerable constriction. In order to restrict the length of the twisting assembly and, thereby, to avoid any undesired weakening of the cutting tube proper, the fitting ring 36 is, as shown, coupled axially slidably but non-rotatably to the tube 1, in order to allow for the decrease in length to which a short torsion sleeve is submitted when being twisted. Preferably the ring 36 is held in its extreme position by means of a snap lock 48 which snap lock will yield to a given pulling force.

In order to enable a further decrease in length of the cutting tube proper, which is favorable with a view to the stroke of the press used for pressing the sampler into the soil, the grooves 41 may have a helical outline as'shown in FIG. 6B. The pitch of these grooves should be such that the displacement necessary for releasing a lug 42 from a groove end is recovered in rotating the coupling tube, so that the free travel between pulling and pushing may be reduced by about onehalf.

When the sampler is withdrawn from the soil, the extension tubes 3 are successively unscrewed. Then, at the same time, the corresponding sections of the supporting tube 18 are separated from one another by cutting both the strip of adhesive tape connecting two tube sections and the sample inside the tube with the aid of a knife, whereafter the sample is covered with a plate. Then the sample can be transported in the tube section. The cutting can also be done with a cutting plate which, at the same time, serves as a cover plate. The cutting can also be done with the aid of a cutting thread which is connected to an electric direct current source for locally increasing the water pressure during the cutting as a result of the voltage difference, and, thereby, decreasing the intergranular pressure, causing the friction ot the cutting thread to be reduced.

Particularly the lower fitting ring 12 may end into a thin elastic lip which, together with another substantially parallel lip in alignment with the inner wall 7, defines a slot, so that, when the outer tube 1 is upset during pressing, the width of the slot is not appreciably reduced, in order to avoid clamping of the hose.

Instead of the cage consisting of rods 14 and a surrounding tube 17, a tube provided with inwardly directed longitudinalribs may be used, which ribs serve the same purpose as the rods.

Within the scope of the invention many variations are still possible.

We claim:

1. A method for taking an undisturbed soil sample with the aid of a cutting tube with a sharp cutting mouth, an annular chamber being disposed round the bottom end of this tube, in which chamber a transversely stretchable hose may be arranged which may enter into the interior of the sampling tube through a slot near the cutting mouth, and may be carried along with the penetrating sample, as a result of which this sample is completely enclosed by the hose, characterized by the steps of introducing a coaxial supporting tube into the cutting tube, which coaxial supporting tube extends down to the vicinity of the slot of the hose chamber, the inner diameter of this tube being only slightly larger than the outer diameter of the sample surrounded by the hose, and introducing a lubricating fluid at the upper end of said supporting tube in order to fill the space between the hose and the supporting tube.

2. The method according to claim 1, wherein a sup porting liquid is introduced into the hose chamber at least in the vicinity of its exit slot for keeping the hose free of the slot and transversely supporting the sample at least in the vicinity of said slot, characterized in that the supporting liquid is poured into the interspace between the supporting tube and the cutting tube, the latter communicating with the hose chamber.

3. The method according to claim 2, characterized in that the lubricating liquid is immiscible with the supporting liquid in order to avoid that the supporting liquid be carried along with the hose. 4. The method according to claim 1, characterized in that the surface tension and the viscosity of the lubricating liquid and the width of the interspace between the supporting tube and the sample are such that, as the sample penetrates into the supporting tube, the lubricating liquid remains in said interspace, but a transverse inward deformation of the sample in consequence of the static pressure of said liquid and the expulsion of the liquid layer by the outward pressure of the sample is avoided.

5. The method according to claim 1, characterized in that the lubricating liquid has a greater adhesion to the wall of the supporting tube than to the wall of the hose.

6. The method according to claim 1 characterized by the steps of extending, during the cutting, the supporting tube by supporting extension tubes disposed within the cutting tube proper, the length of said supporting extension tubes corresponding to that of the extension tubes of the cutting tube proper, said supporting extension tubes being placed with their terminal faces abutting each other and being connected to each other in a sealed manner by means of an adhesive tape, and after withdrawal of the cutting tube from the soil and the subsequent loosening of the extensions of the cutting tube, separating the individual supporting extension tubes from each other by cutting the adhesive tape and the sample, and covering the cutting planes with covering plates.

7. The method according to claim 6, characterized by cutting the adhesive tape with the aid of a covering plate having a sharp edge.

8. The method according to claim 6, characterized in that the sample is transported within the supporting tubeand supporting extension tubes.

9. The apparatus for taking an undisturbed soil sample, comprising a cutting tube having a cutting mouth, an annular chamber disposed round the interior of the lower end of said cutting tube, into which a hose can be inserted, a sample tube arranged within said cutting tube, said annular chamber communicating with the interior of the sample tube by means of a circular slot disposed in the vicinity of said cutting mouth, fitting means disposed in the vicinity of said circular slot, and a detachable rigid supporting tube sealingly fitting into said fitting means, and being coaxially supported in said cutting tube, said sample tube defining said hose chamber and is provided at the inside with longitudinal grooves, the ribs between said grooves contacting said supporting tube, said grooves connecting the lower end of said hose chamber with the interspace between the supporting tube and the portion above the hose chamber of the cutting tube proper and its extensions.

10. The apparatus according to claim 9, characterized in that the sample tube includes a thin-walled inner tube disposed round a cage consisting of longitudinal rods which contact said inner tube and the supporting tube.

11. The apparatus according to claim 10, characterized in that, at their lower ends, the rods of the cage are mounted in a lower fitting ring supported in the circular slot of the hose chamber and, at their upper ends, are mounted in an upper fitting ring supported in the inner wall of said cutting tube above said hose chamber, said fitting rings being provided with recesses between the fixing points of the rods, which recesses communicate with the interspace between the cutting tube and the supporting tube above said chamber, the ring portions between these recesses forming guiding and supporting faces for the supporting tube.

12. The apparatus according to claim 11, characterized in that the upper fitting ring is secured in the cutting tube by means of a ball joint, the lower fitting ring being separate from the cutting tube and being supported by the rods only.

13. The apparatus according to claim 12, characterized in that the lower fitting ring is provided with an inner shoulder forming the fitting for the supporting tube, the diameter of the opening in this fitting means ring below said shoulder being at least about equal to the inner diameter of the supporting tube.

14. The apparatus according to claim 12, characterized in that the lower edge of the lower fitting ring is widened outwardly and downwardly, defining, together with a ring which is correspondingly bevelled at its inside and is secured in the cutting mouth portion of the cutting tube, the circular slot of the hose chamber, the latter extending substantially tangentially to the entering sample.

15. The apparatus according to claim 18, characterized in that the fitting ring ends in a resilient lip, and in that the adjacent inner wall of the lower fitting ring extends substantially parallel to it.

16. The apparatus according to claim 9, characterized in that the supporting tube consists of separate tube sections, the length of which being about the same as that of the extension tubes of the cutting tube proper, which tubes sections may be placed together with their terminal faces against each other, the lower tube section fitting into the fitting at the lower end of the cutting tube having a length corresponding to the length of the cutting tube proper.

17. The apparatus according to claim 16, characterized by covering plates for the tube sections of the supporting tube by which the sample pieces present in these tube sections can be covered at the location of the connection between two tube sections after the sample has been cut through.

18. The apparatus according to claim 9, provided with a flexible sleeve disposed above the hose chamber, said sleeve being fastened with both ends in a ring, the lower end of which being unrotatably connected to the lower cutting tube portion, and the upper end being coupled to a coupling tube which is rotatable but not slidable with respect to the cutting tube, which coupling tube may be firmly connected to the first extension tube in order to twist said flexible sleeve by rotation of said coupling tube and thereby pinching the sample disposed within said sleeve, said upper ring and coupling tube being provided with locking means for maintaining said torsion sleeve in its twisted position, characterized in that at the location of the torsion sleeve the supporting tube possesses a wall portion, the thickness of which is reduced from the outside in order to make the supporting wall yieldable in that region so that it can be pinched flat by the torsion sleeve.

19. The apparatus according to claim 18, characterized in that the coupling between the coupling tube and the lower cutting tube comprises two grooves in the outer surface of the coupling tube, which are symmetrically distributed over the surface, and have an arc length of about which grooves are axially extended at their ends, the inner wall of the cutting tube being provided with two lugs fitting into a corresponding groove, all this in such a manner that in their extreme positions the coupling tube and the cutting tube arenon-rotatably coupled to each other, but are axially movable with respect to one another, so that, in one extreme position, when the cutting tube is pressed into the soil, and in the other position, when this tube is withdrawn, transverse stopping faces of the coupling tube and the cutting tube proper are capable of contacting each other for transmitting the compressive and pulling forces respectively.

20. The apparatus according to claim 19, characterized in that the grooves in the cutting tube have such a helical shape, that the coupling tube in being rotated is axially displaced over a distance which is about equal but is opposite to the free travel of the coupling tube between its pressing and pulling positions.

21. The apparatus according to claim 18, characterized in that the lower ring of the torsion sleeve is non-rotatably but axially movably coupled to the cutting tube by means of a longitudinal key.

22. The apparatus according to claim 21, characterized in that the lower ring of the torsion tube canbe maintained in its lower position by means of a snap lock, until, during twisting of the sleeve, a certain pulling force has been exceeded.

23. The apparatus according to claim 9, characterized by a clamp for closing the upper end of the hose and provided with guiding lugs which are connected to the clamp and which abut the inner wall of the supporting tube so that the upper side of the hose is held substantially symmetrically with respect to the wall of the supporting tube.

24. The apparatus according to claim 23, characterized in that the clamp comprises a circular clamping plate provided with lugs, which plate, while interposing the free edge of the hose, may be clamped on a closing plug disposed within the hose.

25. The apparatus according to claim 24, characterized in that the guiding lugs are spaced from the 28. An apparatus for taking an undisturbed soil sample, comprising a cutting tube operable for being pressed into the soil without rotation from the soil surface and having a cutting mouth at the lower end thereof, coaxial extension tubes removably connectable to the upper end of said cutting tube and extending uninterruptedly to the soil surface, the bore of said extension tubes being substantially equal to the bore of said cutting mouth and thereby to the diameter of the sample to be taken, an annular recess provided in the inner wall of said cutting tube in the vicinity of said cutting mouth, said annular recess being terminated at its lower end with a rounded annular groove, a coaxial inner tube disposed within said cutting tube so as to define with said annular recess an annular chamber for a hose communicating with the interior of said inner tube by a circular slot resulting between the lower end of said inner tube and said annular groove, a removable, rigid, sample support tube insertable into said inner tube, fitting means provided on said inner tube for sealingly supporting said sample support tube near said slot and for axially spacing said sample support tube from said inner tube, the inner diameter of said sample support tube being substantially equal to the bore of said cutting mouth and being in alignment therewith, whereby said extension tubes are usable as a transport container for the sample cut by said cutting mouth and surrounded by said hose drawn from said annular chamber through said slot.

29. An apparatus according to claim 28 further comprising piercing means within said cutting tube, said extension tubes being rotatably connected to said cutting tube and operable for actuating said piercing means while said cutting tube is stationary due to the friction cause by the surrounding soil.

Claims

2. The method according to claim 1, wherein a supporting liquid is introduced into the hose chamber at least in the vicinity of its exit slot for keeping the hose free of the slot and transversely supporting the sample at least in the vicinity of said slot, characterized in that the supporting liquid is poured into the interspace between the supporting tube and the cutting tube, the latter communicating with the hose chamber.

3. The method according to claim 2, characterized in that the lubricating liquid is immiscible with the supporting liquid in order to avoid that the supporting liquid be carried along with the hose.

4. The method according to claim 1, characterized in that the surface tension and the viscosity of the lubricating liquid and the width of the interspace between the supporting tube and the sample are such that, as the sample penetrates into the supporting tube, the lubricating liquid remains in said interspace, but a transverse inward deformation of the sample in consequence of the static pressure of said liquid and the expulsion of the liquid layer by the outward pressure of the sample is avoided.

8. The method according to claim 6, characterized in that the sample is transported within the supporting tube and supporting extension tubes.

19. The apparatus according to claim 18, characterized in that the coupling between the coupling tube and the lower cutting tube comprises two grooves in the outer surface of the coupling tube, which are symmetrically distributed over the surface, and have an arc length of about 170*, which grooves are axially extended at their ends, the inner wall of the cutting tube being provided with two lugs fitting into a corresponding groove, all this in such a manner that in their extreme positions the coupling tube and the cutting tube are non-rotatably coupled to each other, but are axially movable with respect to one another, so that, in one extreme position, when the cutting tube is pressed into the soil, and in the other position, when this tube is withdrawn, transverse stopping faces of the coupling tube and the cutting tube proper are capable of contacting each other for transmitting the compressive and pulling forces respectively.

22. The apparatus according to claim 21, characterized in that the lower ring of the torsion tube can be maintained in its lower position by means of a snap lock, until, during twisting of the sleeve, a certain pulling force has been exceeded.

25. The apparatus according to claim 24, characterized in that the guiding lugs are spaced from the clamping plate by means of axially extending connecting pieces.

26. The apparatus according to claim 24, characterized in that in the center of the clamping plate and vertically directed thereto a pin is disposed, to which a pulling string can be fixed for guiding the upper end of the sample.

27. The apparatus according to claim 26, characterized in that in the vicinity of its free end the pin is provided with a number of symmetrical guiding lugs abutting the inner wall of the supporting tube.

28. An apparatus for taking an undisturbed soil sample, comprising a cutting tube operable for being pressed into the soil without rotation from the soil surface and having a cutting mouth at the lower end thereof, coaxial extension tubes removably connectable to the upper end of said cutting tube and extending uninterruptedly to the soil surface, the bore of said extension tubes being substantially equal to the bore of said cutting mouth and thereby to the diameter of the sample to be taken, an annular recEss provided in the inner wall of said cutting tube in the vicinity of said cutting mouth, said annular recess being terminated at its lower end with a rounded annular groove, a coaxial inner tube disposed within said cutting tube so as to define with said annular recess an annular chamber for a hose communicating with the interior of said inner tube by a circular slot resulting between the lower end of said inner tube and said annular groove, a removable, rigid, sample support tube insertable into said inner tube, fitting means provided on said inner tube for sealingly supporting said sample support tube near said slot and for axially spacing said sample support tube from said inner tube, the inner diameter of said sample support tube being substantially equal to the bore of said cutting mouth and being in alignment therewith, whereby said extension tubes are usable as a transport container for the sample cut by said cutting mouth and surrounded by said hose drawn from said annular chamber through said slot.