US2810289A - Oedometers - Google Patents

Description

Oct. 22, 1957 s. J. BUTTON oEDoMETERs Filed Jan. 19, 1956 ATTORNEY United States Patent Oce 2,810,289 Patented Oct. 22, 1957 OEDOMETERS Sidney John Button, Ealing, London, England, assignor to Ground Explorations Limited, London, England, a British company Application January 19, 1956, Serial No. 560,251

4 Claims. (Cl. 73-94) This invention relates to oedometers.

An oedometer, or consolidation apparatus, as it is commonly called, is used for measuring the compression of a sample of soil when the sample is subjected to a constant load.

One disadvantage of existing consolidation apparatus is that it is necessary for a laboratory assistant to take readings at relatively short intervals of time, and eventually to plot all the readings obtained in order to ascertain the rate of compression.

The present invention provides an oedometer `comprising means for applying a constant uid pressure to a soil sample to determine the consolidation of the sample under constant load, and means for automatically recording the consolidation.

The invention also provides an oedometer comprising an abutment member, a movable member, and means for applying a selected constant uid pressure to said movable member to move it towards said abutment member, whereby a sample interposed between said abutment and said movable member may be subjected to a constant load and the compression of the sample under that load may be measured.

There is further provided by the invention an oedometer comprising a cylinder, a piston movable in said cylinder under tluid pressure, a control valve adapted to control the supply of fluid pressure to said cylinder to maintain a constant loading on said piston, and means for supporting a sample, the arrangement being such that a selected constant load can be applied to the sample by the application of uid pressure to said piston to to determine the consolidation of the sample under constant load.

One construction of oedometer according to the present invention will now be described, by way of example only, reference being made to the accompanying drawing which shows a sectional side elevation of the oedometer.

ln this construction a soil sample is housed in a cylindrical ring 11 and rests on a porous stone 12, the latter fitting within a lower ring 13 on which the lower edge of the ring 11 rests. The lower ring 13 ts in a depression in the base of a liquid container 14. The sample is held in position in the container by a locating ring .15 which is secured by three clamping screws 16 (only two of which can be seen in the view illustrated), which latter engage in the base of the container 14.

A further porous stone 17 iitting within an upper ring 18 rests on the top of the soil sample 10 and is engaged by an abutment plate 19. The abutment plate 19 is apertured to form a seating for a metal ball 20, the latter being held on its seating by an adjustable stud 21 which is in threaded engagement with a cross-beam 22. 'The cross-beam 22 is supported at each end by vertical support members 23, only part of one of which is visible in the view illustrated, the members 23 being mounted at their lower ends in the base 24 of the apparatus. Thus, the cross-beam 22 is ixed relative to the base 24, and

the position of the abutment plate 19 can be adjusted relative thereto by rotation of the stud 21 which, after adjustment, is xed in position by the lock nuts 25.

The outer diameter of the upper ring 18 is less than the inner diameter of the cylindrical ring 11, and it will be clear that the soil sample 10 can be compressed between the stones 12 and 17 by upward pressure applied to the container 14. Moreover, such compression can be effected in the presence of water which is held in the container 14, and for this purpose grooves 14a are formed in the base of the container 14 to admit water to the underside of the porous stone 12.

In this construction the upward pressure is provided by uid pressure which is applied to a piston 26 movable in a cylinder 27 which is Xed relative to the base 24. The duid pressure applied to the piston 26 is transmitted to the container 14 by a connecting rod 28.

The uid pressure may be derived from a source of any known kind, but with the present apparatus it is convenient to use oil from a reservoir in which the oil is maintained under pressure by compressed air supplied from any suitable source such as a motor driven pump. The oil pressure applied to the cylinder 27 being controlled by means of a valve 29 which is also mounted on the base 24. A pipe from the oil supply reservoir is connected to the valve inlet 29a, and the valve outlet 2911 is connected by a fluid line 30 to the interior of the cylinder 27. The valve body is also provided with a relief port 29C through which under conditions to be eX- plained oil is returned to the oil supply reservoir. The valve 29 comprises a plunger 31 by which a force due to the uid pressure applied to the piston 26 is balanced against a weight 32 to maintain the loading upon the sample proportional to the weight 32. The lower end of the plunger 31 is provided with a passage 31a, the horizontal position of which terminates at a mid-portion 31h of the plunger which is of reduced diameter to leave a clearance with the inside of the valve body 29. With the plunger 31 in the position shown the inlet 29a communicates with the passage 31a and the reservoir is in direct communication with the cylinder 27. The pressure in the reservoir will normally be such that the force applied to the lower end of the plunger 31 will become greater than the opposing force due to the weight 32, and consequently the plunger 31 will rise and cut-off the inlet 29a from the passage 31a. Should the pressure in the cylinder 27 still be such that the upward force is greater the plunger 31 will continue to rise until the mid-portion 31h of reduced diameter uncovers the port 29C. The resulting reduction in pressure due to escape of oil from the cylinder 27 through the passage 31a and port 29e will cause the plunger 31 to fall, and it should come to rest in a position at which both ports 29a and 29e are cutoi`r. In this-way the loading on the sample is maintained substantially constant at a value proportional to the weight 32 irrespective of fluctuations in the pressure in the reservoir. Moreover any desired loading within the range of pressure available from the compressor is readily obtained by suitable alteration of the weight 32.

For recording the movement of the container 14 it is provided with an arm 33, a projection 33a upon the end of the arm 33 engaging one end of a pivoted lever 34, the other end of which carries a stylus 35. The fulcrum 34a of the lever 34 is positioned so that the movement of the stylus 35 corresponds to a magnified movement of the container 14. The stylus 35 has a rounded end of extremely small diameter, e. g. 0.00.1 of an inch, which engages a surface of a Celluloid strip 36 fixed on a circular drum 37 rotated at a predetermined rate by means of a clock motor 38. It will be appreciated that as the sample is compressed and the container 14. nieves upwards the Stylus 35 will be dis placed laterally relative to the movement of the Celluloid strip 36 and a trace will be `formed on the strip 3 i 6"I 'he stylus 35 acts in known manner to produce a ow of the surface o f the Celluloid material resulting in the formation of a trough with corresponding ridges on either side. After completion of a test the strip 36 can be examined by optical projection, preferably with magnification, in order to determine the rate and extent of compression af the, sample` is mounted so that its pressure on the strip 36 can be adjusted.

1t will be clear that an pedometer of the form described can be set up and then be left with the minimum of attention until. the automatic recording is Completed at the and 0f. the isst period, whish period may extend with periodically increased load for as much as six days. The necessity for an assistant to take readings continuously is thereby avoided with consequent saving in labour, and furthermore the record is obtained in readily readable manner without the necessity for plotting curves from the readings as with existing apparatus. A further disadvantage of existing apparatus is that the lever system used `therein for loading the sample has required a heavy, and therefore cumbersome, framework and has also suffered from the drawback that false readings may result from vibration transmitted to the machine. The elimination of the lever `system and consequently the heavy framework enables the present apparatus to be of much more compact form.

It will be understood that where two or more oedometers are used only a single fluid reservoir need be provided, although separate control valves are required for each apparatus.

Although the use of oil has been referred to, other fluid ymedia may be used. Thus, compressed `air may be used in conjunction with a pressure control valve of known form.

What l claim is:

l. In an oedometer, an abutment, a first porous stone engaging Said abutment, an open-ended soil sample housing having a uniform internal` cross-section, a second porous stone, each of said porous stones being positioned adjacent one end ofsaid housing respectively, said first stone having `a cross-section similar to the internal crosssection of said housing and being slightly smaller than said internal Across-section whereby s aid rst stone can 4enter said housing to compress against ,the second stone a soil sample ,contained in said housing and restrained from lateral movement by said housing, a cylinder, said cylinder having a port through which fluid under pressure is admitted, a piston movable Ain said cylinder under .fluid pressure, a connecting rod secured to said piston, a liquid containing vessel mounted on said connecting rod, said liquid containing vessel having a base on which said second stone rests with said first stone `and said housing located Within said vessel whereby consolidation can be effected in the presence of liquid, a fluid-pressure regu- `lating valve for maintaining tluid under substantially constant pressure, and a fluid carrying connection between said valve and said cylinder port.

Preferably, the stylus 35` 2. ln an oedometer, a fixed abutment, a first porous stone engaging said abutment, an open-ended soil sample housing; a'second porous stone, each of said porous stones being positioned adjacent one end of said housing respectively, said first stone being smaller than the opening in the end of the housing adjacent which it is mounted whereby said first stone can enter said housing to compress against the second stone a soil sample contained in said housing and restrained from lateral movement by said housing, a cylinder, said cylinder having a port through which fluid under pressure is admitted, a piston movable in said cylinder under fluid pressure, a connecting rod secured to said piston, a liquid containing vcsswel mounted on said connecting rod, said liquid containing vessel having a base on which said second stone rests with said first stone and said housing located within said vessel whereby consolidation can be effected in the presence of liquid, a fluid-pressure regulating valve for maintaining fluid under substantially constant pressure, and a fluid carrying connection between said valve and said cylinder port.

3. Ionian =oedoxneter, an abutment, an abutment engaging member, a first porous stone, said first porous stone bearing against said abutment engaging member, an open-ended soil sample housing having a uniform internal cross-section, a second porous stone, each of said porous stones being positioned adjacent one end of said housing respectively,'said first stone having a cross-section similar to the linternal cross-section of said housing and being slightly smaller than said internal cross-section whereby said iirst stone can enter said housing to compress against the second stone a soil sample contained in said housing and restrained from lateral movement by said housing, a cylinder, said cylinder having a port through which `fluid under pressure is admitted, the position ,of 4said abutment relative to said cylinder being adjustable, a piston movable in said cylinder under fluid pressure, a connecting rod secured to said piston, a liquid containing `vessel mounted on said connecting rod, said liquid containing vessel having a base on which said second stone rests with said first stone and said housing locnitcd within said vessel whereby consolidation can be effected in the presence of liquid, a fluid-pressure regulating valve fi?! maintaining fluid under substantially constant pressure, and a fluid carrying connection between said valve and said cylinder port.

4. An oedorneter according to claim 3, comprising a beam fixed relative to said cylinder, said abutment comprising a stud in screw-threaded engagement with said beam.

References Cited in the file of this patent UNITED STATES PATENTS

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