Soil sampler

TECHNICAL FIELD

The invention relates to a soil sampler, as well as to a method for taking soil samples.

BACKGROUND OF THE INVENTION

Soil samples are taken at a desired depth by means of a sampling tube, which is vibrated, screwed, driven, etc. into the ground by means of a drill string attached to the upper end thereof, until the desired depth is reached. The distal end (the lower end) of the sampling tube is provided with a valve, such as a cone, that is coupled to the sampling tube and closes a receiving space for the soil. An aid, such as a gripper, is lowered from above through the hollow drill string to receive the soil sample, with the coupling between the valve and the sampling tube disconnected. Subsequently, the drill string including the sampling tube is pressed deeper into the ground with room being made for the soil in the receiving space because the soil stops the valve with respect to the sampling tube.

Mechanical means such as balls, springs and pawls are used for coupling/uncoupling of the valve to/from the sampling tube. In actual practice, however, action of the mechanical means may quickly be impeded by soil particles.

An object of the invention is to overcome the above problem.

A further object of the invention is to provide a soil sampler that is simple in construction and is capable of working reliably over the long term.

Another further object of the invention is to provide a soil sampler that is well-suited for taking soil samples in a layer below a layer of granular material.

SUMMARY OF THE INVENTION

The present invention provides a soil sampler comprising a sampling tube having a receiving space for receiving a soil sample, the receiving space being limited in a radial direction by a wall, being open in a distal direction for permitting soil to enter and in a proximal direction being limited by a transverse wall, the transverse wall having line means for supplying and discharging fluid to the receiving space and with means for closing the line means, a free plug or piston being placed in the receiving space closely fitting in there and moveable between the transverse wall and the distal area of the sampling tube and the transverse wall and the plug or piston defining a sealed chamber for fluid when the plug or piston is situated at a distance from the transverse wall.

Thus, use is made of an incompressible fluid body for stopping the soil during movement of the end of the sampling tube to the wanted starting level. To permit entry of the soil, the fluid is permitted to escape via the line means. Mechanical provisions at the distal end of the sampling tube are not required. Long-term reliable action is guaranteed. The plug or piston has the same function as the known cone, but is freely slidable within the receiving space, without connection means to the sampling tube. When sampling occurs through one or several layers of material, particularly granular material, the receiving space can remain closed until the starting level for taking the soil sample has been reached.

Preferably, the plug or piston has a distal surface that is a part of the front surface of the soil sampler. The distal surface has a conical distal surface when the consistency of one or more of the soil layers necessitate a pointed-shaped end for penetration therein.

Preferably, the plug or piston is provided with a cavity in at least one of its axially oriented surfaces. The press force against the radial boundary of the receiving space and thus sealing against fluid leakage as well as against passage of soil material past the plug or piston are improved.

Optimization of the sealing against fluid leakage is obtained when the plug or piston at the proximal side is in liquid-sealing engagement with the wall surface of the receiving space according to a line shaped contact.

A comparable measure can be taken at the distal side of the plug or piston for counteracting soil leakage.

Preferably, the plug or piston has a diabolo-like or hourglass shape.

Preferably, the line means comprise a fluid duct extending through the transverse wall. A valve that can be remotely controlled is present for selectively opening the fluid duct. Preferably, the valve is a one-way valve that is biassed against the distal end of the fluid duct. It is furthermore preferred that the valve comprises a valve disc and a valve rod connected thereto, the valve rod extending through the fluid duct to the proximal side of the transverse wall and being biassed at that location by means of a compression spring. Preferably, the fluid duct is adapted for selective discharge of fluid from the receiving space. When the receiving space is filled with fluid, the valve will prevent escape. When it is desired to let the fluid escape, the valve is operated by pressing against the valve rod by means of a lowered weight, so that the fluid can flow out of the receiving space, corresponding to the volume of the received soil.

Discharge of the fluid can occur via the same duct. It is preferred, however, that the line means comprise a separate and closable supply duct for the fluid.

The supply duct also supplies fluid to the receiving space after raising the soil sampler in order to press out the soil sample.

Preferably, the sampling tube is provided with a core catcher at the distal end to prevent a soil sample of noncohesive material from spilling out after the soil sample has been received.

It may be desirable to pack the soil sample. To that end, according to the invention, means are provided for at least radially enveloping the soil sample received in the receiving space.

In one embodiment, the enveloping means comprise a sleeve arranged at the distal end of the sampling tube such that it can be unwound and extending with a closed end over the open distal end of the receiving space. The sleeve can then be pulled along and unwound by the entering soil.

In case there is a plug or piston, it may be advantageous in the preparation of the soil sampler that the plug or piston is connected to the sleeve.

In an alternative embodiment, a liner is placed in the sampling tube, which liner covers the inner surface of the sampling tube at the location of the receiving space. The liner is already at the desired place prior to the soil sample being taken. It is preferred that a fluid seal is placed between the liner and the sampling tube in order to close off a possible leakage path for the fluid in the receiving space.

Preferably, the plug or piston is in engagement with the inner surface of the liner.

The present invention also provides a method for taking soil samples, wherein a sampling tube having an open end giving access to a receiving space for the soil sample is filled with fluid, is forced into the ground until the location is reached where the soil sample is to be taken, the fluid is given the opportunity to escape while pushing the sampling tube deeper into the ground so that the wanted soil enters the receiving space.

The invention thus provides a method wherein the fluid filled receiving space is sealed to the outside with a fluid sealing free piston, wherein the soil moves the piston to the inside while urging the fluid out when the soil enters.

After disconnecting the cone in known soil samples, soil samples can only be taken from the same location. One or several of the preferred constructions according to the invention discussed above, however, permit closing of the receiving space again at any wanted moment, so that any remaining fluid and the soil already received forms a sealing at the distal end of the sampling tube.

To that end, the invention provides that the receiving space is only partially filled with soil, the fluid is stopped again from escaping, the sampling tube is urged further into the ground to a lower spaced apart desired location, the fluid is given another opportunity to escape while pushing the sampling tube deeper into the ground so that the wanted soil enters the receiving space.

After the soil sampler has been raised, the receiving space is preferably filled with a pressurized fluid to urge the soil sample out of the sampling tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described in greater detail on the basis of a number of exemplary embodiments shown in the attached drawings, in which:

FIG. 1

is a longitudinal sectional view of a lower end of a first embodiment of a sampler according to the invention;

FIG. 1A

is a cross-sectional view of a free piston used in the embodiment of the sampler according to

FIG. 1

;

FIG. 2

is a longitudinal sectional view of a lower end of a second embodiment of the sampler according to the invention;

FIG. 3

is a longitudinal sectional view of a portion of a third embodiment of the sampler according to the invention; and

FIG. 4

is a longitudinal sectional view of a portion of a fourth embodiment of the sampler according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In

FIG. 1

is shown a sampler

1

having a stainless steel sampling tube

2

of a length of about 1.5 meters and a cutting shoe

3

made of hardened metal with a sharp cutting angle. The shoe is screwed on the lower end of the sampling tube via a threaded connection

23

. The cutting shoe

3

defines a passage

4

to the inside of the sampling tube

2

.

A core catcher

5

is attached to the inner surface of the cutting shoe

3

. The core catcher

5

is provided with lips

6

that can be bent away radially to the outside to allow soil to pass in an upward direction but prevent movement of the soil in a downward direction. Core catchers are generally known and are specifically used when a sand sample is to be taken.

The sampling tube

2

forms a chamber

7

that is bounded at the upper end by a wall

9

. A valve

10

is present in a passage

28

in the wall

9

and abuts a seat

12

for sealing. The valve

10

is provided with a valve rod

11

that is biassed in an upward direction by means of a spring

13

so that the valve

10

seals off the passage

28

around the valve rod

11

. The wall

9

is furthermore provided with a duct

14

extending from the chamber

7

to the outside and is closed off by a removable plug

15

.

The sampling tube

2

is provided with a screw thread

26

above the wall

9

for connection to a drill string (not shown).

The chamber

7

provides room for a free piston

8

which can be made of hard rubber. As shown in

FIG. 1A

, the piston

8

has a more or less diabolo-like or hourglass shape having an uppermost circumferential edge

16

and a lowermost circumferential edge

17

and cavities

18

and

19

on the top side and the bottom side.

The sampler

1

of

FIG. 1

can be used as follows: The plug

15

is removed and a source of an incompressible fluid, such as water, is connected to the duct

14

. The fluid flows into the chamber

7

under pressure, and will move the piston

8

to the distal end portion of the sampling tube

2

. When the piston

8

has been moved far enough towards the distal end, the duct

14

is closed by the plug

15

. The chamber

7

is upwardly closed by the valve

10

and downwardly closed by the piston

8

. The shape of the cavity

18

and the circumferential edge

16

prevent downward leakage of the fluid past the circumference of the piston

8

. The piston is kept in its place by friction with the sampling tube wall and by the influence of the closed-off fluid filled chamber

7

.

Subsequently, the soil sampler

1

including the sampling tube

2

and the cutting shoe

3

are inserted into the ground and pushed by means of the drill string to almost above the layer of which the soil sample is to be taken. A weight or another operating means, such as a rod, is then lowered through the hollow drill string to press the end of the valve rod

11

downwards. A stone having a weight of 1 kg on a wire may be used when the soil sampler is screwed into the ground and the spring pressure of the valve need not be high. A rod is recommended when vibrations occur and the spring pressure is about 10 kg. As a result of the downward movement of the valve rod

11

, the valve

10

opens in the direction A. With further downward movement of the sampler

1

, the piston

8

will move upward in the direction B because the fluid is able to flow out of the chamber

7

, through the passage

28

for the valve rod

11

, to the hollow space above the wall

9

. Thus, room is made within the sampler

1

for soil entering via the passage

4

.

When the piston

8

is urged upward under the influence of the soil pressure, the circumferential edge

17

together with a line-shaped contact and the cavity

19

ensure that no soil material can move upwards past the piston

8

.

When the piston

8

is moved upwards inside the sampling tube

2

to a desirable amount, the valve rod

11

is unloaded, and the chamber

7

is closed again. The sampler can then be raised with the piston and the column of soil secured against downward movement. A vacuum may arise in the chamber

7

which offers an upward force against downward movement of the soil sample.

In the case of a non-cohesive material such as coarse sand, further security against downward movement is provided by the core catcher

5

.

After the soil sampler

1

has been brought above ground level, the plug

15

can be removed and the fluid supplied again in order to urge the piston

8

and thus the soil sample in the chamber

7

to the distal end and out of the sampler.

Consecutive samples can be taken from soil layers that are situated at different depths. In that case, when the piston has come halfway of the original chamber

7

, the weight will be removed earlier from the valve rod

11

and then the sampler

1

pressed further downward into the ground, the lower end of the soil sample taken then forming the end plane of the sampler

1

. Possibly, the soil will be compressed to some extent, though this can be taken into account in the analysis of the soil sample.

When, after having penetrated further into the soil two meters, the weight can be brought onto the valve rod

11

again to open the valve

10

and subsequently by pressing in the sampler

1

further in the soil, taking the next sample. Finally, in the manner discussed above, the sampler

1

can be raised again after taking all the wanted soil samples.

In

FIG. 2

, the sampler

1

is given a pointed shape for penetration into the soil. A hard rubber cone

20

with a tip

21

is placed at the lower surface of the piston

8

. The cone can form a separate part with respect to the piston

8

or glued to the piston. The cone is only deployed when the soil in question necessitates such. Further, the operation of the embodiment of

FIG. 2

is the same as that of FIG.

1

. When taking samples using the embodiment of

FIG. 2

, the volume of the cone

20

should be taken into account.

In

FIG. 3

, the soil sample is packed immediately in a so-called sleeve. The shoe

3

is extended in the proximal direction and forms an annular chamber

27

with the extended sampling tube

2

. An end of a rolled up permeable nylon sleeve

21

there is attached in that chamber, the annular chamber

27

thus offering room to a stock

21

a

of the sleeve

21

. The sleeve

21

extends downwards and extends about the lower end of the sampling tube

2

to the inside and upwards, in order to be closed with the other end. The end of the sleeve may be attached to the piston

8

at the location

22

.

When the valve

10

is opened and the sampler

1

is urged downwards into the ground, the soil entering the space below the piston

8

will move the piston

8

upwards and also move the end of the sleeve

21

upwards, the sleeve being able to unwind from the stock

21

a

accommodated in the annular chamber

27

, until the wanted sample length is achieved. After raising the sampler and after screwing the cutting shoe

3

off, the portion of the sleeve that is situated at the outside of the sampling tube

2

can be engaged to make a sleeve sealing there.

In

FIG. 4

, a so-called rigid liner or tubing

24

is also used for the packing of a soil sample. The liner

24

is accommodated in the sampling tube

2

and forms a radial boundary of the chamber

7

. The liner may be transparent. The piston

8

moves within the liner, in the same manner as is the case in the embodiment of FIG.

1

. Between the cutting shoe

3

and the liner

24

, the core catcher

5

is fixed with a flange

26

. To prevent downward escape of the fluid via the upper edge of the liner

24

and past the outer surface of the liner

24

and the inner surface of the sampling tube

2

, a sealing or O-ring

25

is placed at the bottom between the outer surface of the liner

24

and either the sampling tube

2

or the cutting shoe

3

. As a result, the liners can be thin-walled and have a continuous profiling without treatments.

Preferred embodiments of the invention have been described. It is to be understood that the invention is not limited to them and that modifications and changes can be made without going beyond the spirit and scope of the following claims.