Appendix A. Tests for bentonite and slurry fluidproperties

A.1. Marsh funnelviscosity test

Apparatus and testing method shall be generally to AmericanPetroleum Institute Recommended Practice RP 13B-1 as follows.

A.1.1. Equipment The equipment consists of the following:

(a) Marsh funnelA Marsh funnel is calibrated to out-flow one US quart (946ml) of fresh water at a temperature of 70±5°F (21±3°C) in26±0.5 seconds. A graduated cup is used as a receiver.

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SpecificationFunnel cone

Length 12.0 in (305 mm)Diameter (top) 6.0 in (152 mm)Capacity to bottom of screen 1500 ml

OrificeLength 2.0 in (50.8 mm)Inside diameter 3/16 in (4.7 mm)

Screen 12 mesh USHas 1/16 in (1.6 mm) openings and is fixed at a level 3/4in (19.0 mm) below top of funnel.

(b) Graduated cup: one US quart (946 ml)1

(c) Stopwatch(d ) Thermometer: 32–220°F (0–105°C)

A.1.2. Procedure The procedure is as follows.

(a) Cover the funnel orifice with a finger and pour bentonitesuspension through the screen into the clean, upright funnel.Fill until fluid reaches the bottom of the screen.

(b) Remove finger and start stopwatch. Measure the time for mudto fill to one-quart mark of the cup.

(c) Measure temperature of fluid in degrees C.(d ) Report the time to nearest second as Marsh funnel viscosity.

Report the temperature of fluid to nearest degree C.

A.2. Direct readingviscometer

Apparatus and testing method shall be generally to AmericanPetroleum Institute Recommended Practice RP 13B-l as follows:

A.2.1. Equipment The equipment consists of the following:

(a) A direct-indicating viscometer powered by an electric motoror hand crank e.g. Fann Viscometer. Bentonite suspension iscontained in the annular space between two concentriccylinders. The outer cylinder or rotor sleeve is driven at a

1One litre may be used instead of 946 ml, in which case the appropriate

calibration time should be used and the result should clearly reference theone litre volume.

S21Specification for the construction of slurry trench cut-off walls

constant rotational velocity (rpm). The rotation of the rotorsleeve in the fluid produces a torque on the inner cylinder orbob. A torsion spring restrains the movement of the bob, anda dial attached to the bob indicates displacement of the bob.

Instrument constants have been adjusted so that apparentviscosity, plastic viscosity and yield point are obtained by usingreadings from rotor sleeve speeds of 300 rpm and 600 rpm.

Specifications: Direct-indicating viscometerRotor sleeveInside diameter 1.450 in (36.83 mm)Total length 3.425 in (87.00 mm)Scribed line 2.3 in (58.40 mm)

above the bottom of sleeve

Two rows of 1/8 in (3.18 mm) holes spaced 120 deg (2.09radians) apart around rotor just below scribed line.

BobDiameter 1.358 in (34.49 mm)Cylinder length 1.496 in (38.00 mm)

Bob is closed with a flat base and tapered top.

Torsion spring constant386 dyne-cm/degree deflectionRotor speedsHigh speed 600 rpmLow speed 300 rpm

(b) Stopwatch.(c) Suitable container, e.g. the cup provided with viscometer.(d ) Thermometer: 32–220°F (0–105°C).

A.2.2. Procedure The procedure is as follows.

(a) Place a sample in container and immerse the rotor sleeveexactly to the scribed line. Measurements in the field shouldbe made with minimum delay (within five minutes, if possiblefrom sampling) and at a temperature as near as practical tothat of the mud at the place of sampling (not to differ morethan 10°F (6°C)). The place of sampling should be stated onthe report.

(b) Record the temperature of the sample.(c) With the sleeve rotating at 600 rpm, wait for dial to reach a

steady value (the time required is dependent on the mudcharacteristics). Record the dial reading for 600 rpm.

(d ) Shift to 300 rpm and wait for dial reading to reach steadyvalue. Record the dial reading for 300 rpm.

A.2.3. Calculation Plastic viscosity (in cP) =600 rpm reading�300 rpm reading

Apparent viscosity (in cP)=600 rpm reading

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Yield point (in lb/l00 ft2) =300 rpm reading�plastic viscosity

A.3. Specific gravitytestA.3.1. Equipment

The equipment consists of the following.

(a) A set of calibrated weighing scales of sufficient accuracy topermit measurement of weight to within ±0.1 g.

(b) A fixed volume container with a flat upper edge generally nosmaller than 1.0 litre capacity with a closely fitting top plate.

S22 Specification for the construction of slurry trench cut-off walls

A.3.2. Procedure The procedure is as follows.

(a) The empty fixed volume container and the top plate iscarefully dried and weighed and the weight is recorded, Wa .

(b) The fixed volume container is filled to the top with water. Thetop plate is carefully slid across the top of the container toexclude all air bubbles. Any excess water is removed to avoiderrors. The container, top plate and water are carefullyweighed and the weight recorded, Wb.

(c) The fixed volume container is emptied, dried and filled to thetop with fluid to be tested. The top plate is carefully slid acrossthe top of the container to exclude all air bubbles. Any excessfluid is removed to avoid errors. The container, top plate andfluid are carefully weighed and the weight recorded, Wc .

(d ) The specific gravity of the fluid is calculated as followsspecific gravity=(Wc�Wa)/(Wb�Wa ).

(e) The accuracy of the weighing scales should be checked atleast weekly.

A.4. Bleed testA.4.1. Equipment

The equipment consists of a plastic or similar material verticalmeasuring cylinder graduated in 20 ml increments up to 1000 ml,and a membrane or similar to seal the measuring cylinder top toavoid evaporation.

A.4.2. Procedure The procedure is as follows.

(a) Carefully fill the measuring cylinder to the 1000 ml mark withthe cementitious slurry, ensuring that no air is entrapped.Seal the top of the measuring cylinder. Leave to standundisturbed for 24 hours.

(b) When the slurry has stood for 24 hours record the volumeoccupied by the set solids.

S23Specification for the construction of slurry trench cut-off walls