GB2348219A

GB2348219A - Geological probes for acquiring physical and chemical data when driven into a formation.

Info

Publication number: GB2348219A
Application number: GB9903795A
Authority: GB
Inventors: Paul Anthony Jacobs; David John Everard
Original assignee: FUGRO Ltd
Current assignee: FUGRO Ltd
Priority date: 1999-02-19
Filing date: 1999-02-19
Publication date: 2000-09-27
Also published as: GB9903795D0

Abstract

Equipment for testing a geological formation 2 has a first probe 6 for acquiring data related to the physical properties of the formation and a second probe 8 for acquiring data related to the chemical properties of the formation, the probes being housed within an assembly 10, 12 and 14 which is driven into the formation via rod 4 linked to a vehicle such as a lorry 1.

Description

IMPROVEMENTS IN OR RELATING TO GEOLOGICAL TESTING METHODS AND EQUIPMENT This invention concerns improvements in or relating to geological testing methods and equipment.

It is known to employ equipment for the determination of soil type, for example sand, clay etc., and associated mechanical properties, for example shear strength in clays, relative density and hence friction angle in the case of sands. One conventional piece of equipment is a cone penetrometer which carries a suitably instrumented probe measuring tip resistance and friction, which data can then be used to calculate the parameters mentioned above. The penetrometer is pushed into the soil using hydraulic pressure at a constant rate of penetration, eg 20mm/sec. This equipment may be mobile and may accordingly be mounted on a suitable vehicle which will also carry appropriate instrumentation for monitoring the tip resistance and the friction as indicated above.

It is also known to use equipment which interrogates the soil to ascertain its chemical characteristics, in particular to detect the presence of contaminants. An apparatus used for this purpose is in the form of a probe including a heating coil surrounding a Teflon (Registered Trade Mark)-based membrane the hydrophobic nature of which permits the passage of any contaminant whilst preventing the ingress of water. The contaminant is volatilised by the heating coil and the resulting gas passes into a reservoir within the probe from where it is flushed by an inert gas circulating within tubing to surface detectors which serve to analyse and identify the contaminant gas.

This type of probe is typically driven into the ground by a hydraulically operated percussion hammer driving steel rods bearing the probe.

Hitherto it has been necessary to conduct each activity separately using the individual pieces of equipment on their own thereby extending the time required for the investigation.

An object of the invention is to provide an improved way of testing geological formations which facilitates the simultaneous acquisition of soil data in terms of both its physical and chemical profiles.

According to a first aspect of the invention equipment for testing a geological formation includes a first probe for acquiring data related to the physical properties of the formation, a second probe associated with the first probe and adapted to acquire data relating to the chemical properties of the formation, and a drive means associated with the probes for effecting in use penetration of the probes into the formation.

Conveniently the first probe may be provided as part of what is conventionally known as a cone penetrometer which as the name suggests is of conical form and is so shaped as to facilitate penetration into the formation. The probe may be constituted by strain gauges within the cone penetrometer and provided with suitable connections leading to monitoring apparatus remote from the cone end. The cone penetrometer is advantageously formed with a hollow cylindrical section through which the connections pass from the cone end.

The second probe may be one known as a membrane interface probe which incorporates a membrane surrounded by a heater and is contained within a cylindrical housing defining a chamber, the housing being conveniently adapted to connect in releasable manner with the hollow cylindrical section of the cone penetrometer. The connection may be a simple screw threaded connection or an equivalent which will form a firm connection which is not easily disconnectible when in use.

The drive means include one or more rods releasably connectible to one another and to the cylindrical housing of the second probe, together with a drive mechanism for forcing the rods carrying the probes into the geological formation, eg the ground, to test the soil for its mechanical properties and also for any contaminants which may be present.

According to a second aspect of the invention there is provided a method of testing a geological formation including the steps of using the equipment of the first aspect by assembling the first probe in line with the second probe, connecting the drive means to the second probe, actuating the drive means to drive the assembly into the formation, monitoring the probes and ascertaining the physical and chemical properties of the formation.

The second probe may be a membrane interface probe which conveniently has a membrane formed of Teflon (Registered Trade Mark) surrounded by heating coil and has suitable geometry to allow the application of an inert gas to an internal chamber of the housing, in order in use to flush out~ any volatilised contaminant passing into the probe through the membrane.

By way of example only, a method of and equipment for the testing of a geological formation are described below with reference to the accompanying drawing which is a diagrammatic cross section through a geological formation showing the equipment in situ for use in the method.

Referring to the drawing there is shown a vehicle, in this instance a lorry 1, jacked up in position over a geological formation 2 and provided with a drive mechanism (not shown) for a drive means constituted by a hollow rod 4 which carries two probes 6 and 8. The first probe 6 is in the form of what is commonly known as a cone penetrometer having a conical section 10 leading to a hollow cylindrical section 12. The penetrometer houses strain gauges (not shown) with appropriate wire connections led through the sections 10,12.

The probe 8 is in the form of a membrane interface probe which includes a membrane (not shown) and a heating coil (not shown) housed within a cylinder 14 defining a chamber through which the wire connections of probe 6 pass.

The cylinder 14 is screw threaded and connects with the section 12 of the probe 6 in releasable manner.

The rod 4 is screwed into the other end of the cylinder 14 and is connected at its upper end to a drive mechanism carried on the lorry 1, the wire connections of the strain gauges passing through the rod to the vehicle whereon they are connected to instruments (not shown) for monitoring the mechanical properties of the formation 2.

In use, the lorry 1 is appropriately positioned over the formation 2 where geological testing is to be conducted in order to establish its mechanical properties and to determine the presence or indeed the absence of contaminants. The assembly of the rod 4, and the probes 6 and 8 is forced gradually into the formation 2 by the drive mechanism which is conveniently hydraulically powered and can impart a steady driving force to the assembly with the cone penetrometer piercing the formation.

As the assembly penetrates the formation, data are transmitted by the probe 6 to the surface and analysed by suitable instrumentation on the lorry 1 to give values as to the mechanical properties of the soil encountered during penetration. Simultaneously, the probe 8 allows the ingress into its chamber of any contaminants present within the soil and these contaminants are volatilised by the heating coil the power for which is provided by cabling extending through the rod 4 from the surface. An inert gas flushes any contaminant gas generated by the volatilisation through the rod 4 to the surface for analysis.

Accordingly, the acquisition and processing of data relating to both the mechanical properties and the chemical properties of the soil in the geological formation are effected contemporaneously with the advantage of facilitating the survey of the formation and reducing the time expended thereon.

Although the probe 8 has been described principally in relation to the detection of contaminants, it is to be understood that other probes employed to test soil chemistry may equally be used in conjunction with the cone penetrometer, and accordingly the probe 8 may be other than the membrane interface probe.

Claims

CLAIMS: 1. Equipment for testing a geological formation including a first probe for acquiring data related to the physical properties of the formation, a second probe associated with the first probe and adapted to acquire data relating to the chemical properties of the formation, and a drive means associated with the probes for effecting in use penetration of the probes into the formation.
2. Equipment according to Claim 1 in which the first probe is provided as part of a cone penetrometer which is of conical form and is so shaped as to facilitate penetration into the formation.
3. Equipment according to Claim 2 in which the probe is constituted by strain gauges within the cone penetrometer and is provided with suitable connections leading to monitoring apparatus remote from the cone end.
4. Equipment according to Claim 2 or 3 in which the second probe is a membrane interface probe which incorporates a membrane surrounded by a heater and is contained within a cylindrical housing defining a chamber, the housing being adapted to connect in releasable manner with the hollow cylindrical section of the cone penetrometer.
5. Equipment according to Claim 4 in which the connection is a simple screw threaded connection or an equivalent which will form a firm connection which is not easily disconnectible when in use.
6. Equipment according to Claim 4 or 5 in which the drive means include one or more rods releasably connectible to one another and to the cylindrical housing of the second probe, together with a drive mechanism for forcing the rods carrying the probes into the geological formation to test the soil for its mechanical properties and also for any contaminants which may be present.
7. Equipment for testing a geological formation substantially as hereinbefore described with reference to the accompanying drawing.
8. A method of testing a geological formation including the steps of using the equipment according to any one of the preceding claims by assembling the first probe in line with the second probe, connecting the drive means to the second probe, actuating the drive means to drive the assembly into the formation, monitoring the probes and ascertaining the physical and chemical properties of the formation.
9. A method of testing a geological formation substantially as hereinbefore described with reference to the accompanying drawing.