Boring or penetrating the earth – Processes – Sampling of earth formations
Reexamination Certificate
2001-07-27
2003-11-11
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Processes
Sampling of earth formations
C175S020000, C175S050000
Reexamination Certificate
active
06644423
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and method for conducting geotechnical and geoenvironmental measurements using direct push tools, and more particularly to a latching and retrieval system that allows the in situ interchange of several different tools including, but not exclusively, an electric cone penetrometer, a soil core sampler, a soil vapor sampler, and a grouting device, all through an embedded direct push rod string without requiring withdrawal of the string. The device also allows the collection and retrieval of soil core samples from multiple depths during a single penetration without requiring withdrawal of the rod string.
BACKGROUND OF THE INVENTION
Currently, the use of multiple direct push tools during a site characterization (i.e., piezocone, chemical sensors, core sampler, grouting tool) must be accomplished by withdrawing the entire penetrometer rod string to change tools. This practice results in multiple penetrations being required during characterization of a site, and to subsequently seal the resulting multitude of holes with grout.
SUMMARY OF THE INVENTION
The present invention allows multiple tools to be interchanged during a single penetration without withdrawing the rod string from the ground. This allows more work to be accomplished and reduces overall costs as time is not wasted pulling rods back out of the ground to change tools or retrieve soil core samples.
The implementation of a wireline tool approach to direct push technologies is unique from drilling implementations because in contrast to drilling (1) direct push incorporates direct sensing tools at the tip of the rod string, (2) direct push relies entirely on the transmission of axial force through instruments at the tip of the rod string to penetrate the earth, and (3) direct push tools are used to measure in situ stresses, electrical properties, the presence of chemical, and other properties as a means of characterization. Because of these differences direct push uses smaller diameter casings than drilling, with relatively greater wall thickness, and requires the accommodation of electrical cabling and/or optical fibers within the rod string.
The wireline system for multiple direct push tool usage of the present invention is composed of several components which are similar in function to conventional direct push and cone penetrometer technology (CPT) equipment used for in situ geoenvironmental. site characterization. Conventional equipment uses either a heavyweight push truck to advance tools into the earth under static load (cone penetration testing), or a percussion hammer approach using a lighter rig. The electronic probes are instrumented and signals are transmitted to the surface via electrical cable and/or fiber optics strung through the center of the hollow push rods. Also typical is the simple collection of multiple soil core samples.
With the wireline system of the present invention, the same method is used to advance the rod string into the earth. However, in the present invention, the first rod (i.e., the deepest one) has a provision for a latching mechanism that allows various tools to be locked into and unlocked from the rod string, as well as retrieved and deployed through the rod string while the rod string remains embedded in the ground. This system allows instrumented probes and samplers, as well as other tools, to be used during a single penetration.
The wireline system consists of six major components:
rods,
latching mechanism,
soil core sampler,
piezocone module,
vapor sampler, and
grout module.
Rods: The push rods have a relative wall thickness (about 19% of the diameter) exceeding that a typical drive casings used with drilling technologies because direct push systems do not rely on rotary action, cutting bits, or augers to remove material from the path of the rod string, and thus must support the transmission of greater axial load relative to casing diameter than drilling systems in order to penetrate the earth. Typical direct push rod diameters range from about one inch to two and a quarter inches.
The wireline rod string of the present invention has a two-inch outer diameter and a one and one-quarter inch inner diameter. The shouldered joints of the one-meter rod segments are joined by double-lead rope threads which connect faster and sustain greater loading than V-threads.
The rod string optionally incorporates occasional rod expanders (one on every fifth or sixth rod in the string). Expanders are rings welded to the outside of the rods which widen the borehole beyond the normal outside diameter of the rod segments as they pass into the earth, thus creating an annular void between the earth and the normal outer rod surface which alleviates sidewall friction that can accumulate along the embedded length of the rod string. By this action, the expanders enable deeper penetration in some soils than would be achievable without them when using the system.
Latching Mechanism: The latching mechanism comprises two main components, one stationary and the other removable. The stationary component is also the lowermost push rod segment. It is a specialized segment called the tool housing which embodies the receiving mechanism for the removable element. The removable element is the lock assembly.
The lock assembly employs two horizontally opposed, hinged locking dogs which lock the tools into place by rotating outward to occupy a receiving groove in the inside surface of the tool housing. The dogs are held in the locked position by a locking wedge which slides vertically between them. This dog arrangement allows the axial stress on the direct push tools from application of static force, rapid percussion, or other dynamic loading to be distributed over a greater bearing area than on systems used in conventional drilling.
This fulfills the unique requirement of the direct push application for more bearing capacity than required in wireline drilling arrangements because direct push tools encounter the stress of penetration, which must be transferred to the rod string, whereas with drilling, less axial stress is generated on the tools and the outer casing carries most of the bearing load directly. When the locking dogs are in the engaged position, a spring-loaded locking wedge rests between them, preventing retraction of the dogs.
A retraction system allows disengagement of the locking dogs in the latching mechanism by displacement of a spring-loaded locking wedge which travels vertically between the dogs and has a conic outer surface at its base, a cylindrical outer surface above the conic surface, and a smaller diameter shaft above that. The dogs have a vertical inner surface that is beveled at the top, such that when the dogs are not engaged, the wedge must be in a raised position with its conic surface acting against the complementary beveled surface on the dogs, but when the dogs are engaged, the wedge is in a lower position with its vertical surface acting against a vertical surface on the interior of the dogs.
The nature of the contact between the wedge and the dogs disallows retraction of the dogs when the vertical surfaces are in contact, regardless of the inward force exerted on the dogs by the receiving groove, but allows the dogs to retract in response to inward force when the wedge has been raised enough that the conic surfaces are in contact. When not counteracted for retrieval, a compression spring around the shaft of the locking wedge keeps the wedge in the downward position.
The lock mechanism allows the deployed tool to lock into place upon reaching an appropriate depth. A landing nut allows free fall deployment of tools, fine tuning of lock clearances, and easy replacement of the most wear-receiving parts.
The tool housing is a specialized version of the individual rods segments that compose the rod string. First, it is shorter than the one-meter length of the other rods. Second, while the inner diameter of most of the tool housing is identical to that of the individual rods in the string, the tool housing adds a receiving groove o
Bratton Wesley L.
Farrington Stephen P.
Nolet Darren C.
Shinn, II James D.
Applied Research Associates, Inc.
Bagnell David
Fish & Richardson P.C.
Halford Brian
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