ASTM_D_4622_-_86_1993.pdf

Designation:D 4622 86(Reapproved 1993)Standard Test Method forRock Mass Monitoring Using Inclinometers1This standard is issued under the fixed designation D 4622;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes the use of inclinometers forrock mass monitoring,lists some available instruments,out-lines operating techniques and maintenance requirements,andpresents data reduction formulas.21.2 This standard does not purport to address all of thesafety problems,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Significance and Use2.1 An inclinometer is a device for measuring the deviationsperpendicular to the axis of a borehole.Deviations can beconverted to displacements by trigonometric functions.Suc-cessive measurements enable the determination of the depth,magnitude,and rate of lateral movement of an unstable slope.3.Apparatus3.1 Probe-Type InclinometerMany types of inclinometersare available;however,the most commonly used is the probetype.This type consists of a control box and a probe attachedto a cable which is lowered into a flexible casing in a borehole.In some probes,a cantilevered pendulum with resistance straingages,vibrating wire,or inductive transducers is used tomeasure cantilever deflection.Other probes use the Wheat-stone bridge principle,the servo accelerometer principle,or adifferential transformer.The probe generally requires a specialflexible casing with four interior grooves spaced at 90.Theelectrical output from the probe is measured at the control boxand converted to visual display,punched or magnetic tape,orgraphic form.Fig.1 shows a typical inclinometer installation.4.Procedure4.1 Installation:4.1.1 Install the inclinometer casing in a near-vertical holethat intersects the zone of suspected movement.(Measure-ments in non-vertical holes can be made with some inclinom-eters;however,before planning such holes,check manufactur-ers specifications to determine the limitations of the particularinstrument being used.)Extend the hole at least 15 ft(4.5 m)beyond the zone of expected movement into soil or rock inwhich no movement is anticipated.Make allowance for loss ofthe bottom 5 ft(1.5 m)of the hole where sediment accumula-tion may occur.Hold casing in place with a sand backfill or aweak cement grout.Check casings over 50 ft(15 m)deep fortwist(spiraling of the interior grooves)using commerciallyavailable equipment,since some of the casings may bereceived with a built-in twist which would cause considerableerror in observations.4.1.2 Inclinometer casings are commonly installed in either5 or 10-ft(1.5 or 3.0-m)lengths and are available in eitherplastic or aluminum.Plastic casing joints are glued.Aluminumcasings are coupled with aluminum couplings and riveted(seeFig.2).Complete the installed casing using left and right twistin a compensating manner so that the grooves generally are inthe same azimuth from top to bottom.For casings over 50 ft(15 m),consider metal saddles with steel cable support forreducing twisting.Take care to ensure that all joints are sealedsince leakage can introduce fines into grooves and cause errorsin readings or plug the casings.Joints can be sealed withcaulking and taped.Greater installation details can be obtainedfrom manufacturers literature or from other sources.4.1.3 Whether to use plastic or aluminum casing depends onthe situation and the method used.Plastic casing can bedamaged if exposed to sunlight.4.2 Observations:4.2.1 Make initial observations after allowing sufficient timefor the grout around the casing to set or for the backfill to settlewhere sand or gravel is used.Since computation of alldisplacements is based on the position of the casing wheninstalled,verify the initial casing position with at least twoseparate sets of observations.Check these observations closelyto see that they agree within the accuracy of the inclinometerbeing used.Repeat observations until satisfactory agreement isobtained.When initial observations are made,the top of thecasing should be located with respect to a point on the groundsurface which is outside the zone of expected movement byconventional surveying means and its elevation determined.4.2.2 The frequency of observations depends upon severalfactors,the most important of which is the rate of movement.It is necessary to read inclinometers frequently just afterinstallation and,based on these results,to adjust the interval ofobservations.Observations should coincide with observations1This test method is under the jurisdiction of ASTM Committee D-18 on Soiland Rock and is the direct responsibi