[0001] For executing soil investigation, a tube is driven substantially vertically into
the soil, which tube, at or near its lower extremity, is constructed either as a sounding
tube, in which case it is provided with means for determining the resistance against
displacement, e.g. in the form of a so-called sounding cone and/or sounding sleeve,
or as a sampling tool by means of which a sample of the soil can be taken in order
to be investigated in a laboratory.
[0002] In order to press such a tube into the soil, use is made of a device, which is generally
arranged in a vehicle, comprising a yoke which is to be brought into engagement with
the upper extremity of the tube, which yoke is coupled with the pistons of the two
pressure medium cylinders which are arranged at both sides of the tube. As soon as
the tube has been pressed downwards by means of said yoke over the piston stroke,
the yoke is moved upwards again, and another tube is connected to the former tube
by means of a screw-thread connection, and then the tube is pressed further downwards.
The force required therefor can be derived from the pressure of the pressure medium
(generally oil). In the case of a sounding tube this force is generally determined
by means of a transducer provided between the sounding tube and the yoke, and, on
the other hand, force sensors are often arranged in the lower end part, which are
adapted to produce an electrical signal which is a measure for the resistance met
with, and which can be processed further at the surface.
[0003] As soon as the tube has reached the desired or maximum possible depth, a pulling
head is mounted on the yoke, which is adapted to engage the tube in such a manner
that, by means of said yoke, a pulling force can be exerted on the tube. Such a pulling
head can, for instance, comprise a conical inner wall and a plurality of balls arranged
in several layers within a cage, the diameter of said balls in the different layers
being such that, if a tube is inserted through said cage with balls, the conical wall
surface uniformly presses said balls against the tube surface, so that the pulling
force will be transferred onto the tube.
[0004] An objection of such devices is that they are rather bulky and heavy, and must, therefore,
be arranged in or on a vehicle. For measurements in difficultly accessible locations,
in particular in existing buildings, e.g. for determining the bearing capacity of
the foundation in view of reconstruction works, or in difficultly accessible fields,
these known devices are not suitable.
[0005] It is an object of the invention to provide a device for the latter purposes which
does not show these objections and is, in particular but not exclusively, suitable
for being constructed in a transportable and, if required, portable manner.
[0006] To that end, the device according to the invention is characterised in that the driving
means for the tube grip around said tube substantially coaxially.
[0007] In a first embodiment, said driving means comprise a single cylinder having a piston
and associated piston rod which are made hollow, and this in such a manner that the
tube can be led through the interior thereof, said piston rod being connected to a
head by means of which the pressing and pulling forces .can be transferred on the
tube. This unitary construction without a yoke provides a substantial simplification
in respect of the known constructions with two cylinders, and,furthermore, leadsto
substantially smaller dimensions, and, moreover, a pressure acting on the tube in
an accurately axial direction is ensured.
[0008] In a second embodiment of the invention, the driving means comprise at least one
unit consisting of a pair of mutually oppositely arranged driving wheels with a concave
rim profile adapted to the shape of the tube to be driven, at least one of said wheels
of such a unit being connected to a driving motor, in particular a hydraulic motor,
and,in particular, several units can be superposed-along the tube, means being provided
in each unit for driving the wheels towards one another so as to increase the clamping
force.
[0009] With such a device the tube can be driven continuously itself, hnt it is also possible
to drive thereby an auxiliary tube which is provided with means adapted to be brought
into engagement with the tube to be driven into the soil, and corresponding to the
means used in the first embodiment.
[0010] If the driving means operate in a discontinuous manner and are to be reset when providing
or taking away an extension tube section, preferably a special coupling element is
used which is arranged in a horizontal sliding guide connected to the driving means,
so as to allow this element to be slid away laterally for clearing the passage for
a tube, and this element can be constructed as a pressing or pulling head respectively,
said guide being adapted to allow the replacement of a pressing head by a pulling
head and vice versa.
[0011] For application in the case of a sounding tube with an inner rod which is connected
to a measuring element, the pressure head can be provided with a rotatable fitting
with two bores of a different diameter, the narrower one forming an abutment shoulder
for the upper extremity of the upper tube section but allowing the inner rod to pass
so as to bring said inner rod into engagement with a superposed force meter, whereas
the wider bore also passes the sounding tube so that the latter itself will, then,
engage said force meter. In the latter case, for instance, the lateral friction in
the soil along the sounding tube can be measured.
[0012] For retracting the tube, preferably a special pulling head is used comprising a sleeve
surrounding the tube in which a plurality of slightly upwardly inclined strips of
metal or the like are arranged having,.at their free extremity, a concave rounding
adapted to the tube periphery. By means of such a head the friction force required
for the pulling force can be distributed more evenly over the tube surface, so that
the latter will not be damaged, this in contrast to the above-mentioned pulling heads
with balls which, in a rather small number, are being brought into engagement with
the tube wall.
[0013] When using a sounding tube with an inner rod, the extension tube sections are preferably
provided with inner rods which are secured against falling out, this in contrast to
the known constructions.
[0014] If electrical force transducers or the.like are provided in the lower portion of
the sounding tube, a pressing or pulling head resp. is to be used which is provided
with recesses for passing a measuring cord. Furthermore it can be advisable to arrange
the current source for.the measuring circuit in the lower part, and then, in particular,
the inner rods of the sounding tubes sections can be used as a conductor for signal
circuits, said inner rods being provided with coupling means adapted to interconnect
adjacent rods electrically; the contact resistance between the various inner rod sections
will, then, have no influence on the signal available at the transducers. The time-consuming
and troublesome stringing of the sounding tubes on an electric cable is, then, superfluous.
[0015] Instead of electrical signal transfer, also modulated radiation can be used, and
then, in the lower portion of the sounding tube, a radiation source, in particular
a laser diode, and in the upper end portion of this tube a photo-diode or the like
will be arranged. The inner tube diameter is, preferably, chosen as large as is compatible
with the strength of the tube so as to keep free a direct radiation path even in the
case of bending of the tube. It is also possible to polish the inner wall so as to
allow, if necessary, radiation transmission by reflection, but then care should be
taken to avoid disturbing signal broadening by transit time differences, e.g. by a
suitable choise of the modulation shape or by screening off undesired radiation directions
near the photo-diode.
[0016] It can sometimes be favourable to include in the lower portion of the sounding tube
a memory in which the measurement results can be stored, which can be read out later
after retraction of the sounding tubes, and a timing signal should, then,, be recorded,
allowing to correlate the measurements with the insertion depths recorded at the surface.
As a memory, besides a usual electronic memory, also a small tape recorder with micro-cassettes
can be used.
[0017] Such a tube can also be constructed as a soil sample cutter, an improvement being
obtained by accommodating the usual hose,used for reducing the friction between the
soil sample and the tube wall, in a chamber surrounding the sample space of the tube,
said chamber being situated between the cutting mouth at the lower extremity of the
tube and the exit slot between said chamber and the sample space, so that the hose
provided in this chamber can be pulled straightly upwards through the slot, intrusion
of soil particles into said chamber being hampered, and damaging the hose in the slot
being avoided then, so that the use of a supporting liquid,as is required in the current
soil sample cutters in which the hose is deflected by 180
0 in the slot,will be superfluous.
[0018] Such a device for driving a tube into the soil should be directed vertically as well
as possible. To that end, as usual, hydraulically actuated jacks can be used by means
of which the carrier of the device, in particular a vehicle, can be supported. According
to the invention, preferably an inclination sensor is used then, consisting of a housing
filled with oil in which an electrically conductive body is resiliently supported,
which body will contact electrical contacts provided around the circumference as soon
as the housing is not directed exactly vertically, which body and contacts are included
in a control circuit for the pressure medium supply. Inclination meters to be provided
in sounding tubes adapted to measure the inclination of the tube,so as to correlate
the inclination with the depth measurement,are known per se. For directing a device
of the present kind, however, inclination meters have not yet been used. The sensor
according to the invention allows to direct the device in a fast and precise manner.
[0019] The invention will be elucidated in more detail below by reference to a drawing,
showing in:
Fig. 1 a lateral view, partly in section, of a first embodiment of the invention;
Figs. 2A and B a lateral view, partly in section, of a special pulling head for such
a device, and a top view of an element of this pulling head resp.;
Fig. 3 a section of a special pressing head with a measuring body for such a device;
Fig. 4 a diagrammatic top view of an other embodiment of a device according to the
invention;
Figs. 5A, B and C highly simplified representations of different means for transmitting
signals in such a device;
Fig. 6 a simplified representation, partly in section, of a cutting tube to be used
in such a device; and
Fig. 7 a diagrammatic cross-section of a simple inclination sensor for such a device.
[0020] In Fig. 1 a first embodiment of the device according to the invention is diagrammatically
shown, which device is intended for pressing a tube 1 into the soil and, respectively,pulling
it therefrom again, which tube is, in particular, a sounding tube.
[0021] This device comprises an annular cylinder space 2 defined between an outer wall 3
and a coaxial inner wall 4, the inner wall 4 defining a space 5 in which the tube
1 fits with some play.
[0022] In the cylinder space 2 an annular piston 6 sealingly contracting the walls 3 and
4 by means of sealing rings ? is slidable. This piston 6 is connected to a tubular
piston rod 8 guided by means of seals 9 in a cap 10 closing the space 2. At the upper
end of the piston rod 8 a flange 11 is mounted on which a horizontal sliding guide
12 is provided in which a rim 13 of a pressing head 14 to be described below is horizontally
slidable, so that, when sliding away this head, the inner space 5 of the inner wall
4 becomes accessible from above so as to insert a tube 1 into it, which tube can be
an extension tube which can be screwed on another tube section 1 already pressed downwards.
[0023] The piston 6 is shown in its lowest position, and can be moved upwards by supplying
a pressure medium, e.g. oil, the stroke length corresponding to the length of the
tube sections from which the tube 1 is to be assembled. After having slid away the
head 14 in the highest position, another tube section can be introduced into the space
5 and screwed on the preceding tube section, after which the head 14 can be slid back
so that it can be brought into engagement with the upper extremity of the tube. Thereafter
the pressure medium will be supplied to the upper side of the piston 6 so as to press
the tube 1 further into the soil.
[0024] The cylinder wall 3 is mounted in a foot 15 which is immobilised in respect of the
soil in a manner not shown. This foot is, for instance, mounted on a sufficiently
heavy vehicle, but can also be fixed by means of ground anchors or the like. The latter
will be the case if the device is constructed as a portable one which is adapted for
being used in inaccessible places (e.g. in a basement or the like).
[0025] Such a device requires little space, since only one cylinder without a bridge piece
is used. Only the guide 12 is laterally protruding, but can be relatively short. The
pressure medium source can be mounted separately from the device, and can be coupled
thereto by means of pressure hoses.
[0026] In order to retract a tube 1 pressed into the soil, the rim 16 of a pulling head
17 according to Fig. 2 can be slid into the guide 12. Instead of the usual pulling
heads with balls bearing on a wedge-shaped surface and adapted to contact the outer
side of the tube 1, which may locally indent the tubes, use has now been made of a
plurality of lips 13 made of hard steel or the like which are fixed at a slight upward
inclination in the wall of the head 17, and are provided, at their free extremity,
with a recess with a rounded boundary edge having a curvature which corresponds to
that of the external surface of a tube 1. The number of lips 18 depends on the width
thereof, the depth of the recess, and the required force.
[0027] As soon as a tube 1 arrives into the space between the lips 18 from below, the rims
of the recesses 19 come into contact with the tube wall. When retracting the head
16, the tube 1 is gripped firmly between the lips 18. Since the clamping force has,
now, been distributed over a much larger surface portion of the tube wall than in
the case of clamping balls, the tube wall will not be damaged. On pressing downwards
the head 17, the lips 18 will be released automatically, and the head can be removed
from the tube.
[0028] In Fig. 3 a cross-section of a special embodiment of the pressure head 14 is shown,
which serves, at the same time, as a force meter. In this case the tube 1 comprises
an inner rod 20 which is guided slidably in the tube 1, and is, at the lower end,
connected to a measuring cone or the like for determining the soil resistance. Each
extension tube section is provided with such a rod 20, and the end faces of adjacent
rods 20 can contact each other. In order to avoid that the rods 20 fall out of the
corresponding tube sections, each rod is provided with one or more rings 21 which
can abut against a corresponding shoulder 22 in the tube section 1 in question so
as to prevent falling out.
[0029] In the head 14 a piston 23 is situated, against which the rod 20 of the uppermost
tube section will bear when the head is pressed on the tube section. The space 24
above the piston 23 communicates, by means of a fitting 25, with a pressure meter
or force transducer,not shown,for measuring the force acting on the rod 20.
[0030] The end face of the tube 1 bears on a shoulder 26 which is in a fixed position in
respect of the head. This shoulder forms a part of a rotatable insert 27, and is defined
by a through bore 28 in said insert through which the rod 20 extends upwards. Transversely
to the bore 28 a second wider bore 29 is formed in the insert. If the insert 27 is
turned 90
0 by means of a handle 30, the wider bore 29 is positioned in alignment with the tube
1. This bore is wider than the tube 1 so that, then, the end face of the tube 1 will
bear against the piston 23. This position will be used if, for instance, the adhesion
force exerted on the tube 1 by the soil is to be measured.
[0031] Fig. 4 shows an other embodiment of the device of the invention for pressing a tube
into the soil. This device comprises at least one unit 31, but, if required, a plurality
thereof can be superposed. Each unit comprises a pair of wheels 32 and 33 with an
outer rim of substantially semicircular cross-section, which wheels thus define a
substantially circular cavity 34 in which a tube to be driven will fit. The wheel
rims can be roughened or can be provided with a friction covering in order to increase
the grip on such a tube. The wheel 33 is contained in a yoke 35 coupled to a pressure
medium cylinder 36 by means of which this yoke can be pressed against the other wheel
32 so as to improve the grip on the interposed tube still more.
[0032] The shaft 37 of the wheel 32 is coupled to a hydraulic motor 38 adapted to drive
the wheel 38. If a larger driving force is desired, also the shaft 39 of the wheel
33 can be coupled to a motor 40. The driving force can be increased still further
by increasing the number of units 31.
[0033] Such a unit can, for instance, be used to drive a tube 1 directly so as to obtain
a substantially continuous drive. Coupling extension tube sections can take place
during driving. It is, however, also possible to use such a unit for driving a tube
corresponding to the piston rod 6 of Fig. 1, adapted to connect thereto a pressing
head 14 and/or a pulling head 17.
[0034] Instead of a pressure head 14 with a force meter according to Fig. 3, other force
measuring apparatuses can be used, in particular measuring cones or the like with
electrical force transducers. In that case a simple pressing head without measuring
bodies can be used, but, then, said head should be provided with a recess for passing
the measuring cord. For the measuring cord is to be stringed through all the tube
sections to be used since the use of extension cords with contact plugs and sockets
would lead to too high contact resistances. Of course pressing heads constructed in
a different manner can be used instead which, if desired, can be constructed as a
pulling head too. Such measuring cords are, by their nature, troublesome. The invention
provides a number of possibilities allowing to work without such measuring cords.
[0035] As shown in Fig. 5A, a central rod 20 can be used instead of a measuring cord, which
rod needs not to be slidable, and can be provided, at an extremity, with a fitting
41 in which the extremity of the rod 20' of an adjoining tube section will fit more
or less tightly so as-to obtain an electrical connection, and the tube sections 1
themselves serve as a return conductor. It can, then, be advisable to arrange the
current source 22 for the measuring circuit near the transducer 43 in the lower part
of the tube 1, so as to ensure a sufficient voltage near the transducer 43 independent
of the contact resistance in the couplings between the rods 20'. The transducer 43
can be provided with a circuit which is adapted to transform the measurement results
into suitable measurement signals, e.g. in digital form.
[0036] Instead thereof it is also possible to use, for the signal transfer, modulated radiation,
and then, as shown in Fig. 5B, the transducer 43 can be connected to a radiation source
44, e.g. a laser diode, which can send directed radiation through the interior of
the tube, and at the upper extremity of the tube 1 a radiation receiver, e.g. a photo-diode,
will be arranged. The tube 1 is, preferably, made as wide as is compatible with the
strength of the tube, so as to maintain an unimpeded passage for the radiation even
in the case of bending of the tube. It is also possible to polish the inner wall of
the tube 1 in such a manner that the radiation will be transferred by successive reflections,
and, then, care should be taken that only radiation with a given path length can reach
the receiver, and radiation with a different path length is screened there so as to
avoid unsharpness in the signal transmission caused by path length differences.
[0037] Fig. 5C shows still another solution in which the transducer 43 is coupled to a memory
45 in which the measurement results can be stored. After the tube is retracted again,
the measurement results can be read out from said memory. Timing signals should be
recorded then at the same time so as to allow to relate the measurements to the-insertion
depth which is continuously recorded above ground, this also with the associated timing
signals. Such a memory can, for instance, be formed by a small tape recorder with
micro-cassettes.
[0038] Such a tube 1 can also be constructed as a sample cutter for taking soil samples.
It is usual to counteract disturbation of the soil samples by wall friction by enclosing
the sample by a hose. This hose is provided, in the known samplers, in an annular
chamber surrounding the tube cavity into which the sample is inserted, and then the
hose can enter the central bore at the lower end of this chamber through an annular
slot, and the hose is closed there so that a penetrating sample pulls the hose along.
Bending the hose around the edge of this slot, however, can lead to damage, and also
soil particles can penetrate into this chamber. Therefore sometimes a so-called supporting
liquid will be used which is supplied to the hose chamber and facilitates pulling
the hose through the slot and, moreover, keeps soil particles out of this chamber.
Furthermore this liquid acts as a lubricant for the hose.
[0039] According to the invention such a cutting tube can be made in a simple manner as
shown in Fig. 6, in which the hose chamber 46 is situated between the cutting mouth
4? at the extremity of the tube 1 and an exit slot 48 for the hose 49, so that the
hose can be pulled substantially linearly from the chamber 46. Damaging the hose in
the slot 48 is prevented then, and, moreover, penetration of soil particles is prevented.
A supporting liquid can, then, be omitted, which considerably simplifies the construction
of the over-all device.
[0040] In order to drive the tube 1 correctly vertically into the soil, the device should
be directed vertically as well as possible. In the case of a device mounted on a vehicle,
generally jack cylinders will be used having piston rods provided with foot plates
which can be driven outwards by a pressure medium such as oil for relieving the springs
of the vehicle, and,, by a separate pressure medium supply towards the different cylinders,the
floor of the vehicle can be horizontally adjusted.
[0041] The invention provides means for considerably accelerating these operations and making
them independent of human intervention and, thus, of errors. To that end a special
sensor shown in Fig. 7 is preferably used. This sensor comprises a substantially cylindrical
housing 50 filled with oil, in which a float 51 of insulating material is provided
which, by means of a spring 52, is kept in the centre when the housing 50 is directed
vertically. In the inner wall of the housing electrical contacts 53 are provided adapted
to contact the float 51 as soon as the housing 50 has been removed somewhat from the
vertical orientation. The spring 52 is, with these electrical contacts, included in
a control circuit by means of which, in correspondence with the orientation of the
float, the pressure medium supply towards the different jacks can be regulated. A
fast, automatic and accurate orientation of the device can be obtained thereby.
[0042] The device according to the invention can also be used for driving a drainage tape
into the ground by means of a protecting tube which is finally retracted again, leaving
a a wedge-shaped driving end piece to which the tape is attached in the soil.
[0043] The embodiments allowing a continuous driving force to be exerted are particularly
suitable for sounding purposes, as an interrupted movement of a sounding tube may
influence the measurement results.
[0044] In the embodiment of Fig. 4 the driving motors 38 and 40 can, of course also be electric
motors,
[0045] Many other modifications are possible within the scope of the invention as defined
in the appended calims.
1. A device for performing soil inspection such as sounding or sampling, comprising
means for fixedly supporting the device in respect of the ground, and means for driving
a tube substantially vertically into the soil and retracting it therefrom again, characterised
in that the driving means for the tube (1) grip around this tube substantially coaxially.
2. The device of claim 1, comprising a cylinder provided with a driving piston having
a piston rod adapted to engage the upper end of the tube, characterised in that the
piston (6) and the associated piston rod (8) are made hollow in such a manner that
the tube (1) can be led through the bore thereof, the piston rod (8) being connected
to a head (14, 17) by means of which a pressing or pulling force resp. can be exerted
on the tube (1).
3. The device of claim 1, characterised in that the driving means for the tube (1)
comprise at least one unit (31), consisting of a pair of opposed driving wheels (32,
33) with a concave rim profile adapted to the shape of the tube (1) to be driven,
at least one of the wheels (32, 33) of such a unit (31) being connected to a driving
motor (38, 40). units (31) are adapted to be superposed along this tube (1).
4. The device of any one of claims 1..3, characterised in that the tube to be driven
is an auxiliary tube provided with means (14, 17) to be brought into engagement with
the tube (1) to be driven into the soil.
5. The device of claim 2 or 4, characterised by a coupling element which is arranged
in a horizontal sliding guide (12) so as to allow the coupling element to be shifted
away laterally and, thus, clearing the passage for a tube (1), which element can be
constructed as a pressing or pulling head (14, 17), the guide (12) being adapted for
substituting a pulling head (17) for a.pressing head (14) and vice versa.
6. The device of any one of claims 1..5, adapted for driving a sounding tube into
the soil, said tube having an inner rod connected to a measuring element, characterised
in that the pressing head (14) is provided with a rotatable fitting with two bores
of a different diameter, the smaller one (28) forming an abutment shoulder for the
upper end of the tube_(1) but letting through the inner rod (20) so as to allow the
latter to contact an overlying force meter (23..25) provided in the pressing head
(14), and the larger one (29) letting through also the tube (1) so that the latter
itself is allowed to contact said force meter (23..25).
7. The device of any one of claims 1..6, adapted for'using sounding tubes with a central
rod, characterised in that the central rods(20) of extension tube sections are secured
against falling aut (21).
8. The device of any one of claims 1..7, adapted to a sounding tube with electric
measuring elements, characterised in that the current source (42) for the measuring
elements (43) is arranged near the lower end of the tube (1).
9. The device of claim 8, in which the various tube sections are provided with a central
rod, characterised in that the central rods(20) are provided with coupling means (41)
adapted for realising an electrical connection between the central rods of adjoining
tube sections (1).
10. The device of claim 8, characterised in that, near the transducers (43) in the
lower portion of the sounding tube (1), a radiation source (44), in particular a laser
diode, is provided, and at the upper end of the tube (1) an element sensitive for
the emitted radiation, in particular a photo-diode, is arranged.
11. The device of claim 8 , characterised in that, near the transducer (43) in the lower portion of the tube,
a memory element (45) is mounted, means being provided for registering a timing signal,
enabling to relate the measurements to insertion depths recorded above ground.
12. The device of any one of claims 1..6, in which the tube is constructed as a sample
cutting tube, which, near its lower end, is provided with a chamber surrounding the
sample cavity and accommodating a hose, which chamber communicates with the sample
cavity by means of an exit slot, characterised in that the sample cavity (46) is situated
between the lower end of the tube (1) and the' exit slot (48).