Borehole stress-meter and method and apparatus for the installation thereof
AssigneeUniversity of Alabama
InventorsDuk-Won Park, Theodore W. Ryan
Life of this patent
Estimating the term…
Abstract
A borehole stress-meter includes a resiliently radially expandable hollow body within which can be positioned a gage plug having strain gages fixed thereto. The interior section of the hollow body is tapered, as is the gage plug so that advancement of the gage plug within the hollow body will cause the gage plug to become prestressed. The hollow body can be inserted into a bore drilled in earth material whose stress is to be measured by an installation or setting tool. Subsequently, the gage plug is advanced within the hollow body so as to prestress the gage plug. The setting tool is then removed and stress may be measured by an appropriate strain indicator.
Claims23
A borehole stress-meter comprising:
- a hollow body having a first longitudinal axis, said body defining an internal bore extending from a first end of said body to a second end of said body, said bore having a cross-section which decreases in area from said first end to said second end, said hollow body including means for permitting resilient radial expansion thereof;
- a gage plug having a shape corresponding to at least a portion of said bore and being sized so that said gage plug can fit in said first end of said bore, and not in said second end of said bore, without causing said radial expansion of said hollow body;
- at least one strain gage fixed on at least one surface of said gage plug, said strain gage adapted for emitting a signal proportional to a strain of said gage plug;
- and
- signal processing means operatively connected to said at least one strain gage for processing said signal.
A method for measuring stress in earth material, said method comprising the steps of:
- drilling a borehole of a first diameter in said earth material;
- providing an expandable hollow body having at least an exterior portion in the form a cylinder with a diameter marginally smaller than said first diameter and having a tapered internal bore;
- inserting into a larger end of said internal bore a gage plug having at least one strain gage fixable thereto;
- inserting said hollow body in said borehole;
- advancing said gage plug in said internal bore towards a smaller end of said internal bore, whereby said hollow body is expanded against said earth material and said gage plug is prestressed;
- and
- processing strain related signals emitted from said at least one strain gage.
Dependencies are inferred from the claim text.