Pressuremeters and other In Situ Testing Equipment Presented by : Louis Marcil, Eng

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Pressuremeters and Pressuremeters and

other In Situ Testing other In Situ Testing

EquipmentEquipment

Presented by : Louis Marcil, Presented by : Louis Marcil, Eng.Eng.

Roctest Webinar April 2012

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INTRODUCTIONINTRODUCTION

1. Pressuremeters (PMT)1. Pressuremeters (PMT)1.1 Description of the Test1.1 Description of the Test1.2 Description of the Equipment (Types of 1.2 Description of the Equipment (Types of Pressuremeters)Pressuremeters)1.3 Main Applications1.3 Main Applications1.4 Advantages and Limitations1.4 Advantages and Limitations

2. Other In Situ Test Equipment2. Other In Situ Test Equipment2.1 Vane Testers2.1 Vane Testers2.1 Cone Penetration Test Equipment (CPT)2.1 Cone Penetration Test Equipment (CPT)

CONCLUSIONCONCLUSION

Presentation OverviewPresentation Overview

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IN SITU TESTING

Proper characterization of mechanical properties of the ground onto which structures are to be built has a great importance.

Rhomboidal ‘bent’ Pyramid, Egypt

Pyramid Initial Slope

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IN SITU TESTING

Means for characterizing the ground:

1)Laboratory Testing

2)In Situ Testing

- Penetration Resistance Measurement (SPT, CPT)

- In Situ Permeability Tests (Packer Test, Rising Head Test...)

- Strength and compressibility testing (PMT, Vane Testing, Plate load tests, Flat Dilatometer…)

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1 Pressuremeters1 Pressuremeters

PMT = An in situ loading test executed by radial expansion of a cylindrical cavity. The stresses are exerted on the walls of a borehole by mean of a pressurized fluid acting on one inflatable membrane.

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1.1 Test Description1.1 Test Description

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TYPICAL PRESSUREMETER CURVE• Progressive loading in steps. Waiting period required at every step for stabilization before recording pressure and radial expansion

• Unload-loading cycle

• Test duration : 10 min

• Standards: ASTM 4719-07 NF P94-110-1, EN_ISO_22476-4

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General Testing Procedure

•Tests executed at various depths in the same borehole

•Common spacings : 1 to 3 m.

•Borehole cannot be done in one pass

•Results are presented for each elevation giving general profile of the soil.

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Pressuremeter modulus (E)Pressuremeter modulus (E)

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Main Parameters:

v

p x V x ) + (1 2 = E b

mR

Where:

- R : Poisson's ratio of the soil/rock

- Vm : the volume of the cavity at mid-point of the testing zone

- : the variation of volume of the cavity due to the variation of the applied pressure

v

pb

Limit pressure (Pl)Limit pressure (Pl)

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The Making of the Borehole = Critical to make successful tests ! ! !

Borehole = Adequate if:

1. Undisturbed Soil

2. Borehole of Proper Diameter

3. Smooth wall borehole


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Various drilling methods suggested in Standards as per type of soils.

Use of rotary drilling with axial injection (towards hole bottom) of mud is applicable in most

cases. Slotted casing in large-gravels soils.

• Ideally: Roller bit for silt, sand, and gravel. 2 7/8 in. to 3 inches. Three-wing bit for clayey soils.

• Diameter of rods must be one or two sizes smaller than diameter of bit to allow good flow up of cuttings

• Do not ram the bit up and down as this will result in an oversized hole

• Popular method : 3-in hollow auger for first portion of the borehole + use of rotary bit in the testing zone only

Go slowly:

Injection pressure: < 500 kPa with borehole full of mud

Bit rotation: < 60 rpm

Flow : < 15 liters per minute

Bit pressure: < 200 kPa (100 kg in a 76 mm borehole)

Typical advance rate: 15 to 25 cm/minute


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1.2 The Equipment1.2 The Equipment

VARIOUS TYPES OF PRESSUREMETERS:

- Pre-Boring vs Self-Boring Pressuremeters

- Volume Variations vs Direct Radial Strain Measurements

- Mono-cellular vs Tri-cellular Probes

- Diameter of the Probe : 33 mm to 95 mm

- Type of Loading: Pneumatic vs Hydraulic

- Reading Mode: Manually vs Automatically

- Working Capacity: 4,000 kPa to 30,000 kPa

- Various Sensitivities

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Soil Pressuremeters:

Trimods Pressuremeter(Radial expansion measurement, hydraulic, mono-cellular probe)

Menard Pressuremeter(Volumetric, pneumatic, tri-cellular probe)

Texam Pressuremeter(Volumetric, hydraulic, mono-cellular probe

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Model PROBEX

Capacity pressure: 30 000 kPa (3500 psi)

Hydraulically loaded Fiberglass-reinforced polyurethane membrane Capacity modulus: 0.01 to 30 GPa approx. Testing depth to (date): 300 meters

Model PROBEX

Capacity pressure: 30 000 kPa (3500 psi)

Hydraulically loaded Fiberglass-reinforced polyurethane membrane Capacity modulus: 0.01 to 30 GPa approx. Testing depth to (date): 300 meters

Rock Pressuremeters:

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Model DMP

Measures radial deformations by

mean of 3 LVDT disposed at 120 °

Capacity pressure: 20 000 kPa

For used in soft to moderately hard

rock (Maximum modulus of 50 GPa)

Rock Pressuremeter / Borehole Dilatometer:


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• Interesting tool because minimizes remolding

• Confined to soils with few gravels


Self-Boring Pressuremeters:

BOREMAC Pressuremeter(volumetric, hydraulic, mono-cellular probe)

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1) Shallow foundations

2) Laterally loaded piles

3) Vertically loaded piles

4) Compaction control

5) Design of pavement

Of less use for slope stability problems and embankments

1.3 Main Applications1.3 Main Applications

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Semi-empirical methods vs. methods based on the theory of elasticity

Semi-empirical method:

1) Bearing Capacity = K x Pl

The factor of proportionality K is function to:

- Relative depth

- Shape of the foundation

- Type of ground

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BqE

BqE

S aM

ppa

M32 9

6,0/9

2.1

2) Settlement :

Ref: Canadian Foundation Engineering Manual

- S is the settlement - EM is the pressuremeter modulus.- qa is the allowable bearing capacity- λ2 and λ3 are the coefficients of shape of footing, (L/B)- B is the width of the footing- αp is a coefficient of structure (function to type of soils and E/Pl)

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3) Lateral Deflection of laterally-loaded structures

P-Y Curve:

Various Methods

Robertson et al.

Example :VGS Reduction of Rock Pressuremeter Tests

Design P-Y Curves 54-inch Diameter Rock Socket

(Courtesy: Failmezger, In Situ Soil Testing, VA)

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Design of High Rise Buildings

Petronas Towers(Kuala Lumpur, Malaysia)

AT&T Tower(Chicago, USA)

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LIMITATIONSLIMITATIONS

• Well-trained operator is required for ensuring: Well-trained operator is required for ensuring:

Making a good boreholeMaking a good borehole

Taking care not to burst too many membranesTaking care not to burst too many membranes

• Soils with large gravels are difficult to test. A slotted Soils with large gravels are difficult to test. A slotted casing might be required.casing might be required.

1.4 Advantages and Limitations1.4 Advantages and Limitations

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ADVANTAGESADVANTAGES

• Versatile: Can be performed in most types of soils and soft rocks

• Gives an in situ stress strain curve

• The loading sequence can be adapted according to the application (long or rapid loading, cyclic loading)

• Close analogy with laterally-loaded piles

• Validity of the test can be controlled from the shape of the curve.

1.4 Advantages and Limitations1.4 Advantages and Limitations

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Various types of in situ tests can be performedVarious types of in situ tests can be performed ::

Penetration Test (SPT, CPT), Vane Test, Plate Loading Test, Flat Dilatometer Test, Packer Test, Penetration Test (SPT, CPT), Vane Test, Plate Loading Test, Flat Dilatometer Test, Packer Test, Compaction Control Test, etc.Compaction Control Test, etc.

2. 2. Other In Situ Testing EquipmentOther In Situ Testing Equipment

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2.1 2.1 Vane Shear TesterVane Shear Tester

• For cohesive soils onlyFor cohesive soils only

• Test DescriptionTest Description

• Quick and EasyQuick and Easy

• Used either for designing of shallow or Used either for designing of shallow or deep foundationsdeep foundations

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2.1 2.1 Vane Shear TesterVane Shear Tester

Su = K (as - af) x C

Where:Su = the undrained shear strength in kg/cm2

C = vane form constant in 10-2 x cm-3 K = calibration constant for the torque recording head in kg

m / cmas = distance in cm between the zero torque reference line to the peak

of the curveaf = distance in cm between the zero torque reference line and the

circular arc scribed during the first 15 degrees of rotation (corresponds to rod friction)

Recording sheets from the Model M-1000 Vane Tester

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2.2 2.2 Cone Penetration TestCone Penetration Test

Dynamic Cone Penetration Test:

Procedure: Record number of blow counts required for trusting a conical point into the ground. Size and shape of the point, weight, and the mass falling distance are standardized.

Used for soil classification and for compaction control.

Model PEM-1 Cone Dynamic Penetrometer

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Static Cone Penetration Test (CPT) :

The most common penetration test.

Pushed into the ground.

Recording of: tip resistance, friction resistance, pore pressure and others.

Models:Models:

-Handsounding Cone Penetrometer (1)-Mechanical Cone (2)-Mechanical Friction Cone (3)-Electric Cones (4)

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Static Cone Penetration Test (CPT) :

Interpretation and use of results:

Soil Classifications using cone and friction resistance.

Determination of various parameters from empirical correlations: For instance:

- Stiffness and relative density in cohesionless soils. - Undrained Shear Strength in cohesive soils.

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CONCLUSIONCONCLUSION

Roctest has specialized in pressuremeters

PMT not a routine testing method

Required well-trained operator

Special attention must be given for the making of the borehole

PMTproves to be a useful tool for applications :

1) Such as for the laterally loaded foundations, and high rise buildings2) Where undisturbed samples cannot be obtained, and where other conventional tests cannot be done (rock & weakly

cemented material)3) On large projects where it is justified to put efforts to get

better information on the soil/rock

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Thank you ! Questions ?Thank you ! Questions ?

(Courtesy of

ODOT)

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Pressuremeters and other In Situ Testing Equipment Presented by : Louis Marcil, Eng