US3611794A

US3611794A - Apparatus and method for determining the soil resistance of a subterranean earth formation

Info

Publication number: US3611794A
Application number: US860262A
Authority: US
Inventors: Pieter J De Geeter
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1969-09-23
Filing date: 1969-09-23
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12

Abstract

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF A SUBTERRANEAN EARTH LAYER BY DRIVING A SOUNDING PIN CARRIED BY A BODY INTO THE LAYER UTILIZING THE WEIGHT OF THE BODY TO DRIVE THE PIN THROUGH THE LAYER. THE FORCES EXERTED ON THE PIN ARE MEASURED AND RECORDED AND SOIL WITHIN THE LAYER IS WASHED AWAY WHILE DRIVING THE PIN THERETHROUGH.

Description

Oct- 12, 1971 P. J. DE GEL-:TER

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF A SUBTERRANEAN EARTH FORMATION 3 Sheets-Sheet 1 Filed Sept. 23, 1969 FIG. 2

L w 5 O 5 4 5 3 5 4 m. 6 5 .\4 7 8 5 4 uw 6 5 I f M M 4 9 3 4 5 7 3 4 2 n 9 2 I /q//r f IIL l IIITIIII l IJ 7 4 f H 19|. m 9 2 FIGl 3 FIG.

INVENTOR:

P|ETER J. DEGEETER BY:

@ZW )PEM/MM Has ATTORNEY Oct. 12, 1971 p, 1 DE GEETER 3,611,794

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF A SUBTERRANEAN EARTH FORMATION Filed Sept. 23, 1969 .'5 Sheets-Sheet .'3

72 RTW/4 /f n f/ y es nl 5 e7 i f fr lxs 76/ a l Y M75 f, a 75/ a 4 i '.r/ /8o E /sl 7 74/ r/74 5 f 'l 64 g Y,79

78 iff# INVENTOR:.

PIETER J. DEGEETER JW XW,

HIS ATTORNEY Oct. 12, 1971 p, DE GEETER 3,611,794

APPARATUS AM) METHOD FOR DETERMINING THE SOIL RESISTANCE OF A SUBTERRANEAN EARTH FORMATION 3 Sheets-Sheet Z Filed Sept. 23, 1969 FIG.

FIG. 9

FIG-8 FIG. 7

FIG. II

INVENTOR:

PIETER J. DEGEETER, BY: J

. I5 OQSMJJ HIS ATTORNEY Unted States Patent @mee 3,611,794 Patented Oct. 12, 1971 U.S. Cl. 73-84 6 Claims ABSTRACT or THE DISCLOSURE Apparatus and method for determining the soil resistance of a subterranean earth layer by driving a sounding pin carried by a body into the layer utilizing the weight of the body to drive -the pin through the layer. The forces exerted on the pin are measured and recorded and soil within the layer is washed away while driving the pin therethrough.

BACKGROUND OF THE INVENTION iField of the invention The present invention relates to a method and apparatus for determining the soil resistance of subsurface layers. Particularly, the present invention relates to a method and apparatus for determining the soil resistance of subsurface layers by means of a sounding pin carried by a body for driving the pin through the soil.

Description of the prior art The knowledge of soil resistance or bearing capacity of the soil is of particular interest when erecting heavy structures. vIt is then of utmost importance to know the resistance or bearing capacity of the soil at the site where the structure is to be erected. If, for instance, it is desired to set up a platform supported by legs on the bottom of the sea, such as is often required when drilling oil or gas wells, or when producing oil or gas from such wells, it is iirst necessary to investigate the ability of the sea bottom to support the platform legs in such a way that no impermissible subsidence of those parts of the sea bottom carrying the legs will take place.

It will be appreciated that the requirements for measuring the bearing capacity of the soil apply for marine work as described above as well as for land work.

SUMMARY OF THE INVENTION lIt is an object of this invention to provide `a method and apparatus for measuring bearing capacities, by which a record of the bearing capacity of subsoils may be obtained as a function of their depth. v

It is a further object of the present invention to provide a method and apparatus measuring the properties of subsurface formations wherein this information may be obtained in a very simple and quick manner.V

According to the invention, the sounding pin is driven through the soil under influence of at least part of the Weight of the body carrying the pin, and the soil at a level between the lower end of the body and lthe lower end of the sounding pin is washed away by hydraulic jets to form a hole for the free passage of the body.

The soil may be washed away by hydraulic iets to a level just below the lower end of the sounding pin when the sounding pin has to be driven through relatively hard layers odering a resistance to the sounding pin which is higher than the downward load exerted in the body on the sounding pin. n

The body may be suspended from a flexible tubular element rwhich is run at a substantially*constant'velocity into the hole in which the body driving the sounding pin descends.

The present application further relates to apparatus for determining the soil resistance of subsurface layers comprising a sounding pin carrying elements for measuring forces exerted on the pin, recording means for recording the values of the forces exerted on the pin, a body carrying the sounding pin at one end thereof, at least one nozzle carried by the body at the end carrying the sounding pin, a flexible conduit connected to rthe other end of the body and a passageway forming a communication between the interior of the [flexible conduit and the nozzle.

The apparatus according to the invention may further" comprise a second nozzle or set of nozzles communicating via a second passageway with the iirst passageway, a valve being arranged in this second passageway which valve may be opened by a relative displacement between the sounding pin and the body, and may be closed by a relative displacement between the pin and the body in a sense contrary to the sense of the rst displacement.

In, another embodiment, the apparatus according to the invention comprises a second nozzle or set of nozzles communicating with the interior of the ilexible conduit via a second passageway, a valve being arranged in said second passageway and the flexible conduit, which valve may be opened by a relative displacement between the sounding pin and the body, and may be closed by a relative displacement between the pin and the body in a sense contrary to the sense of the rst displacement.

In still another embodiment, the apparatus according to the invention comprises a second nozzle or set of nozzles communicating with the interior of a second exible conduit via a second passageway, a valve being arranged in said second passageway, which valve may be opened by a relative displacement between the sounding pin and the body, and may be closed by a relative displacement between the pin and the body in a sense contrary to the sense of the rst displacement.

A second valve may be arranged in the rst passageway which valve co-operates with the first valve so as to close the passage through the iirst passageway when the passage through the second passageway is being opened by the first Valve and vice versa.

The valve (or valves) may be coupled to the sounding pin and be loaded by a spring. The valve(s) may also be loaded in the normal working position lby hydraulic pressure to close the valve arranged in the second passageway.

*In another embodiment of the invention, the sounding pin is telescopically arranged with respect to the body between two positions, and loading means are provided urging the pin to the position in which the pin protrudes as farl as possible from the body.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view of the body and the sounding pinA carried thereby, of an apparatus according to the invention;

FIG. 2 is a vertical side view of a frame carrying guide wheels suitable for guiding the ilexible conduit carrying the body and the sounding pin of FIG. 1;

AFIG. 3 is a top plan view of the frame of FIG. 2;

FIG. 4 is a vertical sectional view of apparatus according to the invention wherein the valves arranged in the passageway leading to a first and a second set of nozzles respectively are biased by hydraulic pressure;

FIG. 5 is a view similar to FIG. 4 but with the valves in a diiferent position;

FIG. 6 is a View similar to FIG. 4, but with the valves in such a position that the passageway leading to the rst set of nozzles is closed and the passageway leading to the second set of nozzles is open;

FIG. 7 is a vertical sectional view of a body'and sounding pin vof apparatus according to the invention, which is provided with a single set of nozzles, and in which the pin is automatically retracted when relatively hard layers of the formation are to be passed;

FIG. 8 is a vertical sectional, partly schematic, view of the apparatus according to FIG. 7 in a position in which the pin has touched a. relatively hard formation layer;

FIG. 9 is a vertical sectional, partly schematic, view of the apparatus according to FIG. 7, in which the pin is in the retracted position;

FIG. 10 is a vertical sectional, partly schematic, view of the apparatus according to FIG. 7, when passing through the relatively hard layer;

FIG. 11 is a vertical sectional, partly schematic, view of the apparatus according to FIG. 7, in a position wherein the pin has passed through the relatively hard layer; and

FIG. 12 is a vertical sectional, partly schematic, view of the apparatus according to FIG. 7, wherein the body has passed through the relatively hard layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the apparatus according to FIG. 1, the sounding pin y1 is connected to the lower end of a body 2 by means of a telescoping arrangement. This arrangement comprises a thickened end 3 of the sounding pin 1, which thickened end at the lower side thereof is provided with a. valve body 4 and with its upper part may slide within the cavity 5 formed by a housing 6 which is connected to the inner side of the wall 7 of the body 2 by distance pieces 8. The valve body 4 cooperates with a valve seat 9 which is formed on the lower part 10 of the body 2. This lower part 10 is connected to the body 2 in a suitable (not shown) manner so as to partly close off the open side of the cavity 11 of the body 2, thereby leaving open a circular row of nozzles 12 arranged near the wall 7 of the body 2. The nozzles 12 are directed downwards when the sounding pin 1 is in its operational position. The part 10 further forms a nozzle 13 around the sounding pin 1, which nozzle has the supply thereto closed-off by the valve body 4 when the sounding pin is pressed downwards by the spring 14. This spring 114 is compressed between the thickened end 3 of the sounding pin 1 and the inner end wall 6a of the housing 6 surrounding'the cavity 5. The valve body 4 may be opened by depressing the sounding pin .1 relative to the body 2 thereby further compressing thespring 14.

The nozzles 12 are at one side thereof in communication with the cavity 11 which in its turn communicates via a bore 15 in the body 2 with the interior 16 of a exible conduit 17. The lower end of this conduit is clamped to the body 2 by a suitable clamping means 18.

At least two

electric cables

19 and 20 are incorporated in the wall of the flexible conduit 17. The cable 19 is grounded to the body 2 by means of a suitable screw 21, whereas the cable 20 is passed suitably insulated into a watertight coupling unit 22, in which unit the conduit 20 is connected to an insulated cable 23, which at its other end is connected to the one end of the electric circuit of a straingauge 24 (see dotted lines in FIG. 1) connected to the sounding pin 1. The other end of the electric circuit of the straingauge 24 is grounded via cable -25 to the sounding pin I1, and since the pin 1, valve 4, thickened part 3, housing 6, distance pieces 8, wall 7, and body 2 are all formed by metal, there is a suitable electric connection between the cable 25 and the cable 19.

The electric cable 23 is suitably insulated, and passed through a bore (not shown) in the sounding pin 1, through the cavity 5 in a flexible manner, so as to adapt itself to the various positions of the thickened part 3 of the pin y1 and the housing 6, and through a (not shown) bore in the housing 6, one of the distance pieces 8 and the wall 7 of the body 2. Thereafter it is passed alongside the body 2 and clamped thereto in a suitable (not shown) manner.

The operation of the means for determining soil resistance of subsurface layers as shown in FIG. 1 will now be described. As is shown in FIG. 1 of the drawing, the body 2 and the pin 1 are in the normal working position and suspended from the flexible conduit 17 in a substantially vertical, substantially cylindrical hole 26 which passes through the subsurface formation 27 .of which the soil resistance has to be measured as a function of depth. The manner in which hole 2.6 has been formed will be better understood after having described the way of operation of the present apparatus within the hole 26 as shown, and thus be described hereinafter, in particular with reference to the apparatus as shown in FIGS. 2 and 3.

Liquid under pressure (such as pressurized water) is passed from a suitable source at the surface via the flexible conduit 17 (FIG. 1) and the bore 15 into the cavity 11 of the body 2, and passes through this cavity 11 along the distance pieces 8 to the entrances of the nozzles 12. The liquid is ejected from the nozzles 12 in the direction of the arrows 28, thereby washing away the soil to a depth below the lower end of the body 2, but above the lower end .of the sounding pin 1. As the bottom of the hole 26 is continuously being removed by the washing action of the hydraulic jets issuing from the nozzles 12, the body 2, which is continuously being lowered in the hole 26 by paying out the flexible conduit 17 can descend in the hole 26 unhampered, and the sounding pin 1 will penetrate in the formation under influence of the weight of the body 2.

The resistance which the soil exerts on the sounding pin 1, compresses the pin to a certain extent. The compression of the pin by this resistance as well as by the hydraulic pressure acting thereon, is measured by the straingauge 24. These measurements are communicated to the surface via the

electric cables

19 and 20 and recorded on the surface (not shown) as a function of depth. It will be appreciated that the depths at which the measurements are taken are recorded by measuring the length of the flexible conduit 17 which has been played out into the hole 26. After compensation of the inuence of the hydraulic pressure on the recorded measurements (which pressure is linear to the length of the flexible conduit as played out below the sea level) a recording of the relationship between soil resistance and depth can be made.

Although the straingauge 24 has been shown in FIG. 1 to be located in a part of the sounding pin 1 which is located in the zone of the formation 27 which is not disturbed by the hydraulic action of the jets 28 passing out of the nozzles 12, it will be understood that this straingauge 24 could, with equal result, be arranged in that part of the sounding pin 1 which is out of contact with the formation 27. Those types of measuring apparatuses, however, which have to be in direct contact with the formation 27, are mounted in that part of the sounding pin 1 which is inside the formation 27 during operation of the equipment.

It will be appreciated that the largest value of the Soil resistance which can be measured by the present device cannot be greater than the weight of the body 2 and the sounding pin 1 divided by the cross-sectional area of the sounding pin 1. For example, assuming the total weight of the device having a volume of 30 cubic decimetres to be 240 kilograms and the cross-sectional area of the sounding pin 2 square centimeters, a maximum load capacity of the soil of kg./cm.2 can be measured in a waterfilled hole 26, if the upward forces exerted by the jets 28 are neglected. However, if liquid is used having a specific density greater than l, this latter figure will be somewhat smaller. When encountering formation layers having bearing capacities higher than 105 kg./cm.2, the weight of the device will be insufficient to penetrate the sounding pin 1 deeper into the formation 27. However, the characteristics of the spring 14 have been chosen such, that under this situation in which the full weight of the body 2 rests upon the immovable sounding pin 1, the valve 4 is opened by the weight of the body 2 against the action of the spring 14, thereby opening a passage between the cavity 11 lled with high pressure liquid and the nozzle 13. Consequently a jet of liquid will pass out of the nozzle 13 and onto the formation 27 (as indicated by 29), which jet has sufficient energy to wash away the formation to a level just below the lower end of the sounding pin 1. The boundary of this washed away section has been schematically indicated bythe dashed line 30 in FIG. l.

It will be appreciated that during this passage of the sounding pin 1 through formation layers having a bearing capacity over 105 kg./cm.2, no indication of the exact value of this capacity can be obtained. Once the sounding pin has passed through such formation layer (wherein the action of jets 29 is supported by the action of jets 28 to increase the diameter of the hole 26 sufficiently to obtain a free passageway for the body 2) the exact values of the bearing capacity of the formation 26 can be measured again.

It will be appreciated that the invention is not limited to the particular design of the means for determining the soil resistance of subsurface layers as shown in FIG. 1 and described with reference thereto. Thus the electric equipment as described for taking the measurements of the forces exerted on the sounding pin may widely differ from the one as shown in the drawing. Instead of the design as shown, an amplifier may be arranged for amplifying the signals obtained from the straingauge 24, which amplifier may be placed at a suitable location. The amplied signals are transmitted via two insulated electric cables to the surface. These cables may be incorporated in the flexible conduit 17 (like the cables 19, 20), but may also be separate therefrom or clamped thereto by suitable means.

The way in which the body 2 and the sounding pin 1 are lowered into the formation 27 will now be described in more detail. Although the equipment which can be used for this purpose and which is shown in FIGS. 2 and 3 is especially designed for measuring bearing capacities of formations lying below a body of water, it will be understood that this equipment can also be used for landwork.

The equipment as shown in FIG. 2 comprises a frame 40, which is preferably three-legged, and equipped with two

guide wheels

41, 42 which are rotatably supported by the frame by means of a set of cardan rings. This set comprises a ring 43 pivotally supported by the frame 40 by means of

pivots

44, 45 and a ring 46 which is pivotally supported by the ring 43 by means of pivots 47, 48 (FIG. 3). The

guide wheels

41, 42 are rotatably arranged around pins 49, 50 carried by the ring 46.

A guiding and protecting sleeve 51 for guiding and protecting the body 2 and the pin 1 is connected to the ring 46 by means of

rods

52 and 53.

FIG. 3 shows a top view of the equipment according to FIG. 2. The guide wheel 42 is positively driven by means of an electric motor 54 which obtains its energy via a cable 55, and is connected to the wheel 42 via a suitable (not shown) transmission.

The wheel 41 is freely rotatable around the

4,9 and connected via a suitable transmission (not shown) to a revolution counter 56. The signals obtained from this counter are, as will be explained hereinafter, representative for the length of the flexible conduit 17 which has been played out and consequently representative for the depth at which the sounding pin 1 is operating. These signals are sent via the cable 57 to a recording apparatus (not shown) where they are recorded in combination with the signals obtained from the sounding pin 1.

The ilexible conduit 17 which carries the body 2 and constitutes a passage for the liquid to be fed to the nozzles of the body 2, is passed in the form of a figure eight over the

guide wheels

41 and 42. The diameter of the wheels, and of the cable, and the friction between the wheels and the cable is chosen such that the conduit 17 is passed over the

wheels

41 and 42 at a speed dictated by the electric motor S4 actuating the wheel 42, as long as the body 2 can descend. However, when the body 2 is not moving in a downward direction (e.g. when the jet 29 is operating to break through a layer of high bearing capacity) the flexible conduit 17 will slip over the surface of the wheel 42 and consequently the wheel 41 will no longer be driven by the conduit 17 and the recorder which receives signals from the revolution counter 56 via the cable 57 will indicate that the lowering of the body 2 in the hole 26 has stopped.

When starting measuring operation, the frame 40 having the body 2 suspended in the protecting sleeve 51, is lowered from a ship onto the bottom of the sea 58. This lowering operation is to be carried out by suitable guide lines, cables and anchors but, since it is no part of the invention, will not be described in detail. As the guiding and protecting sleeve 51 enclosing the body 2 is suspended from the frame 40 by means of two cardan rings 43 and 46,V the axis of the sleeve 51 will be vertical, even if the sea bottom is not horizontal.

By starting the motor 54 which is operatively connected to the guide wheel 42, the ilexible conduit 17 is passed over the

guide wheels

41 and 42 and the body 2 is lowered in a vertical direction. The pin 1 on entering the bottom 58 under influence of the weight of the body 2, is compressed and this compression (which is a function of the bearing capacity of the soil 58) is measured and recorded in the manner as described with reference to FIG. 1. At the same time, the length of exible conduit 17 which has passed over the wheel 41 is measured by the counter 56 and recorded together with the information obtained from the sounding pin 1.

The liquid which is being fed to the cavity 11 (FIG. l) ofthe body 1 va the flexible conduit 17 issues from the nozzles 12 in a substantially downward direction and starts to erode the sea bottom 58 locally where the pin 1 has penetrated this bottom over some distance. The local erosive action forms the hole 26 (FIG. 1) which is of sufficient diameter to allow the body to pass therethrough so as to follow the pin 1 which is continuously being pressed into the bottom of this hole under influence of the weight of the body 2. The bottom of the hole is continuously being washed away by the action of the jets 28. The jets 29 come into action only when the weight exerted on the pin 1 is insufficient to allow further progress of the pin 1 in downward direction.

It will be appreciated that the present invention is not limited to the arrangement of nozzles as shown in FIG, 1. If desired, the nozzles may be arranged according to another pattern than the one as shown in FIG. l, provided that there is always one nozzle or a set of nozzles which is suitable to erode during normal operation the soil to a level which is below the body 2 but above the lower end of the pin 1. Further there may be arranged a second nozzle or set of nozzles, from which when relatively hard formation layers are to be passed, hydraulic jets can issue to erode the soil to a level just below the sounding pin, andv which nozzle(s) may be put in operation when the load exerted on the pin is insutlcient to force the pin into the soil. The valve or valves controlling the liquid supply to this second nozzle or set of nozzles may. eg., be operated electrically by receiving an electric signal from the recording means so as to indicate that the maximum load on the pin has been reached. When the hard layer has been passed, the load on the pin will drop below this maximum value, and a signal will be sent to the valve to close the passageway to the second nozzle or set of nozzles. In another manner the valve may be put in operation by a relative displacement between the pin 1 and the body 2 and put out of operation by a relative displacement between these two parts but in a direction contrary to the direction of the rst relative displacement.

If desired, the second nozzle 13 or set of nozzles may communicate with the interior 16 of the exible conduit 17 via a passageway which is different from the cavity'11.

In another embodiment, the second nozzle 13 or set of nozzles may communicate with the interior of a second flexible conduit. This latter conduit and the first conduit 17 may be combined to a single body. It will be understood that in both embodiments as described, a biased valve operated by the pin 1 is located in the passageway leading to the second nozzle or set of nozzles, which valve is operated in the same manner as described with reference to FIG. 1.

Reference is now made to FIGS. 4, and 6, all showing a longitudinal section of an apparatus according to the invention, in which the body carrying the sounding pin is provided with two sets of nozzles. Other than in the apparatus according to FIG. 1, the liquid supply to the nozzles is controlled by a valve system, in such a manner that the two sets cannot operate simultaneously at full energy. The valve system is biased by hydraulic pressure instead of by a spring as in the device according to FIG. l. As can be seen from the drawing, the FIGS. 4, 5 and 6 show the valve system in different positions.

The details, in which the apparatus according to FIGS. 4, 5 and 6 does not differ from the apparatus according to FIG. l, have been omitted. Such details are inter alia the flexible conduit 17, the straingauge 24 and the electric circuit.

In FIG. 4, the pin 61 is being forced into the formation 62 under influence of its own weight and the weight of the body 60. The bottom part 63 of the hole 64 is continuously being eroded by the action of the jets 65. Water under pressure is supplied to the body 60 from a suitable pump (not shown) via a flexible conduit (not shown) carrying the body 60. The ow of water within the body 60 is indicated by the arrows 66.

A valve body 67 is mounted on the pin 61, which valve body is provided with a first valve face 68, ports 69 and a second valve face 70. The first or lower valve face 68 is suitable to co-operate with the lower valve set 71 in the normal operative position of the apparatus as shown in FIG. 4, whereas the second or upper valve face 70 is suitable for cooperation with the upper valve seat 72 in the position as shown in FIG. 6, wherein the apparatus is passing through relatively hard layers.

The pin 61 and the valve body 67 are guided so as to be axially displaceable with respect to the body 60, by the guides 73, the restricted part 74 of the valve housing 75 and the part 76 of this valve housing.

The apparatus according to the invention as shown in FIGS. 4, 5 and 6 comprises two sets of nozzles. The rst set consists of nozzles 77 arranged in the lower wall 78 of the body 60, and the second set is formed by openings 79 arranged around the pin 61 and between the guides 73. The pin 61 is urged in downward position by the difference in load existing between the parts of the valve body 67 exposed to the pressure prevailing in the interior of the valve housing 75 and the parts of the valve body 67 and the pin 61, which are exposed to the pressure prevailing in the hole 64. The difference in pressure existing over these parts is created by the resistance exerted to the flow of water passing through the nozzles 77 arranged in the lower wall 78 of the body 60. Normally the difference in load on the various parts of the pin 61 and the valve body 67 will be suicient to retain the pin in the position as shown in FIG. 4. However, when hard layers are encountered, the pin 61 will move relatively to the housing 60 and be urged into the housing under inuence of the weight of the body 60 which is being lowered in the hole 64.

Thus, if the weight of the body 60 is, e.g. 205 kilograms, and the difference in hydraulic load over the valve 67 and the pin 61 is 200 kilograms, subsoil formations having a bearing capacity of up to 100 kilograms per square centimeter can be measured when the cross-section of the pin 61 is 2 square centimeters. The relative position between pin 61 and body 60 will then be as indicated in FIG. 4. By' meeting a resistance of a value higher than 200 kilograms, the housing 60, weighing somewhat over 200 kilograms, runs over the pin 61 (vide relative position as shown in FIG. 5) until the position as shown in FIG. 6 has been reached, in which position the passageway leading to the nozzles 77 has been closed off, and the passageway leading to the second set of nozzles 79 which are arranged around the pin 61 and between the guides 73 is opened. The flow of liquid supplied via the exible conduit (not shown) to the body 60 then flows through the valve body 67, the ports 69, the valve housing and enters the nozzles 79 at last via the annular passage between the pin 61 and the restricted portion 74 of the valve housing 75 (see arrows 80). The dimensions of the nozzles 79 have been designed such that the water issues therefrom in a powerful jet 81, which is capable of eroding in the relatively hard formation layer the direct surroundings of the pin 61 down to a level which is just below the lower end of the pin 61. Thus, the relatively hard layers in the formation 62 which have a bearing capacity higher than kilograms per square centimeter may be hydraulically washed through at the location where the pin 61 has to penetrate. After having passed through these hard layers, the lower end of the pin enters softer formations. Since the load on the pin is then reduced, the load difference existing over the pin 61 and the valve body 67 will push the pin partially out of the body 60 which results in a shift of the valve system to the position as shown in FIG. 4. Consequently, the jet streams 81 are cut off and the entry to the nozzles 77 are opened, thereby forming jet streams 65 which are able to erode the relatively hard layers of the forarntion during the descent of the pin 61 and the body 60 in the hole 64, since the distance between the nozzles 77 and the hard layers has been reduced as the pin has already protruded in the local hole 82, which has been pre-eroded by the jets 81.

It will be appreciated that the valve system according to the FIGS. 4-6 will in particular be useful for application in equipment which is applied for measuring the bearing capacity of formations having relatively hard layers present therein, which are of relatively small thickness.

An alternative of the apparatuses as shown in FIGS. 1 and 4 will now be described with reference to FIGS. 7-12 which show an apparatus according to the invention in various positions relative to a relatively hard formation layer which is to be passed by this apparatus.

The apparatus as is schematically shown in FIG. 7 in its normal working position and comprises a housing 100, and a sounding pin 101 which is telescopically arranged with respect to the housing 100 and slides in a tubular guide member 102 which with its lower end thereof is connected to the lower wall of the housing 100. In this lower wall, a set of nozzles 103 is arranged which nozzles are directed in such a manner that they create jet streams 104 under different angles with respect to the central axis of the apparatus.

A pin 105 is xed to the sounding pin 101 and slidably arranged in a slot 106 of the guide 102. The sounding pin 101 is movable between two positions which correspond with the end positions of the pin 105 in the slot 106.

Water under pressure is supplied from a suitable source (not shown) to the interior 107 of the housing 100 via the flexible tubing 108 of which the lower end is clamped by clamping means 109 to the upper end of the housing 100. The ow of water is indicated inside the housing 100 by the arrows 110 and outside the housing by the arrows 104.

The pressure drop existing in the liquid over the nozzles 103 also exists over the upper end and lower end of the sounding pin 101, thereby forcing the sounding pin 101 in the position as shown in FIG. 7, wherein the pin 105 rests in the lower extremity of the slot 106 of the guide v102. It will be appreciated that as long as the forces exerted on the lower part 111 of the pin 101 which protrudes in the formation 112 are smaller than the net hydraulic downward force acting on the sounding pin, this pin remains in the position relative to the housing 100 as shown in FIG. 7. The forces exerted on the part 111 compress the sounding pin and the compression is measured in a suitable manner, e.g. by a straingauge (not shown), similar to that described hereinabove. Since the measuring of the compression of the sounding pin and the transport of the measuring results to the surface has already been described with reference to FIG. 1, no further description thereof will be given with reference to FIG. 7 since the same equipment may be used.

If the forces exerted on the part 111 of the sounding pin 101 exceed a predetermined'value, the sounding pin 101 will be pushed into the housing 100. This value is in the present case equal to the net downward force exerted by the hydraulic pressure over the sounding pin 101 increased by the relative mass of the sounding pin. This position is shown in FIG. 8, when the sounding pin 101 cornes to rest during the downward travel thereof in the formation 112 on the top of the relatively hard formation layer 113. In the position as shown in FIG. 9, the sounding pin 101 is as far as possible retracted into the housing 100 (in a position in which the pin 105 is in its extreme upper position in the slot 106 of the guide 102) and the jets 104 which in the relatively soft formation 112 could wash away the formation to a level between the lower end of the housing 100 and the lower end of the sounding pin 101 are then in a position in which they may wash away the relatively hard layer to a depth just below the lower end of the sounding pin -1. The body/pin assembly in the relative position as shown in FIG. 9 then descends through the relatively hard formation layer 113 until the pin 101 passes into the underlying relatively soft formation 114, into which it immediately protrudes under influence of the hydraulic force acting on the sounding pin 101. This situation is indicated in FIG. 1l. Thereafter, the jets 104 wash away the relatively soft formation 114 to a level between the lower end of the housing 100 and the lower end of the sounding pin 101 so as to form a substantially vertical, substantially cylindrical hole 115 through which the body 100, which is being lowered into this hole by paying out the tubular conduit 108 (FIG. 7) at a substantially constant speed.

It will be understood that, if desired, the sounding pin 101 as shown in FIG. 7 may be provided with a piston having a diameter different from the diameter of the pin 101, on which piston acts at one side the pressure in the space 107 and at the other side the pressure which prevails outside the housing 100.

Suitable sealing means may be provided around the sounding pin 101 as well as around any of the other sounding pins as described in this specication so as to separate the high pressure hydraulic zone inside the body 100 from the hydraulic zone outside this body.

It will further be appreciated that the body and sounding pin, as described with reference to FIGS. 4-6 as well as the body and a sounding pin as described with reference to FIGS. 7-l2, may be lowered by means of the equipment as shown in FIGS. 2 and 3. However, any other type of equipment for lowering the body and sounding pin in the formation may be used as well for the equipment according to FIG. l as for the equipment according to FIGS. 4-6 and the equipment according to FIGS. 7-12. Thus, the flexible conduit carrying the body and the sounding pin may be looped at least once around a drum (not shown), which is continuously driven at a substantially constant speed, and thereafter guided past a measuring wheel, the rotation of which is measured and recorded for indicating the way length along which the sounding pin has been lowered in the formation. Obstructions met by the sounding pin in the form of layers of relatively high bearing capacity will momentarily hamper the progress of the body and the sounding pin in downward direction, since the jets will have to erode a hole through these relatively hard layers. During this stalling of the progress, the movement of the flexible tube along the measuring wheel is stopped as the tube slips over the driving wheel.

It will be apprecaited that the speed at which the body and sounding pin descend in the formation depends only on the speed at which the bottom of the hole is being eroded (by jets 23 in FIG. l and 65 in FIG. 4). The maximum speed at which the body and sounding pin may descend is limited by the rotational speed of the driving wheel (wheel 42 in FIG. 3).

I claim as my invention:

1. A method of determining the soil resistance of at least one layer of a subterranean earth foramtion comprising the steps of:

driving a sounding pin carried by a body from the earth surface through said layer utilizing the weight of said body to drive said sounding pin through said layer;

measuring the forces exerted on said sounding pin;

recording the forces being measured; and

washing away soil within said layer while driving said sounding pin therethrough by jetting a uid spray downwardly and substantially parallel to the longitudinal axis of said sounding pin in an amount sufficient to form a hole of suicient diameter to allow the body to pass therethrough.

2. The method of claim 1 wherein the step of washing away soil within said layer while driving said sounding pin therethrough by jetting a fluid spray downwardly and substantially parallel to the longitudinal axis of said sounding pin comprises at least some of the time washing away said soil to a depth above the lower end of said sounding pin.

3. The method of claim 2 wherein the step of washing away soil within said layer comprises the step of washing away said soil byI jetting a fluid spray downwardly and substantially parallel to the longitudinal axis of said sounding pin to a levelat least just below the lower end of the sounding pin when said apparatus encounters a layer of the subterranean earth formation which offers a resistance to said sounding pin greater than the driving force exerted on said sounding pin by the weight of said body.

4. Apparatus adapted to be lowered through a layer of a subterranean earth formation to determine the soil resistance of that layer comprising:

a hollow elongated body; a sounding pin axially slidably connected to one end of the body; measuring elements carried by the sounding pin for measuring forces exerted on the sounding pin; first jetting nozzle means for emitting a iluid jet carried by the body at the end connected to the sounding pin and opening away from the body in a direction substantially parallel to the longitudinal axis of the sounding pin; second jetting nozzle means for emitting a iluid jet around the sounding pin carried by the body adjacentr the sounding pin and opening away from the body in a direction substantially parallel to the longitudinal axis of the sounding pin;

flexible conduit means connected to the end of the body opposite the first and second jetting nozzle means for delivering uid to the body from a source of pressurized fluid.;

passage meanslextending through the body to provide uid communication between the conduit means and the rst and second jetting nozzle means; and

valve means disposed within the passage means and operatively associated with the sounding pin for increasing fluid ow to the second nozzle means as the sounding pin slides inwardly with respect to the body and for decreasing fluid flow to the second nozzle means as the sounding pin slides outwardly with respect to the body.

5. The apparatus of claim 4 wherein said passage means includes at least a first and a second passageway in said body, said first and second passageways being, respectivef 1y, in communication with said first and second nozzle means; and wherein said valve means is arranged in said second passageway, said valve means being coupled to said sounding pin whereby said valve means is opened by a relative inward movement of the sounding pin with respect to the body, and is closed by a relative outward movement of the sounding pin with respect to the body.

6. The apparatus of claim 7 wherein said conduit means includes rst and second flexible conduit means connected to the body; wherein said passage means includes a rst passageway extending through the body to provide uid communication between the rst conduit means and the rst jettng nozzle means and a second passageway extending through the body to provide uid communication between the second conduit means and the second jetting nozzle means; and wherein said valve means is arranged in said second passageway, said valve means being coupled to said sounding pin whereby said valve means is opened 12 by a relative inward movement of the sounding pin with respect to the body, and is closed by a relative outward movement of the sounding pin with respect to the body.

References Cited RICHARD QUEISSER, Primary Examiner C. E. SNEE III, Assistant Examiner U.S. Cl. X.R. 175-50