types of penetrometers..(ubaid ahmed mughal)

8/7/2019 Types Of Penetrometers..(Ubaid Ahmed Mughal)

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UBAID AHMED MUGHAL 2007-CIVIL-44

ASSIGNMENT # 1

VARIOUS TYPES OF PENETROMETERS

Submitted To : Sir Mubashir Aziz

Submitted By : UBAID AHMED MUGHAL 2007-CIVIL-44


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TABLE OF CONTENTS

ContentsASSIGNMENT # 1 ........................................................................................................................................................ 1

VARIOUS TYPES OF PENETROMETERS ....................................................................................................................... 1

Submitted To : Sir Mubashir Aziz ........................................................................................................................... 1

Submitted By : UBAID AHMED MUGHAL 2007-CIVIL-44 ........................................................................................ 1

1) DILATOMETER ........................................................................................................................................... 3

Working & Explanation ...................................................................................................................................... 3

Improvements in Dilato-meter .......................................................................................................................... 4

Soils Parameters ................................................................................................................................................. 4

Advantages ......................................................................................................................................................... 4

Disadvantages .................................................................................................................................................... 4

2) PRESSEUR METER ........................................................................................................................................... 5

Types of Pressure meters ................................................................................................................................... 5

Parameters Obtained ......................................................................................................................................... 6

Advantages ......................................................................................................................................................... 6Disadvantages .................................................................................................................................................... 6

3) STANDARD PENETROMETER .......................................................................................................................... 6

Description and test procedure ......................................................................................................................... 6

Advantages ......................................................................................................................................................... 6

Disadvantages .................................................................................................................................................... 7

4) CONE PENETROMETER ................................................................................................................................... 8

Types of Cone penetration Tests ........................................................................................................................... 8

Parameters Obtained ............................................................................................................................................. 8

Advantages ......................................................................................................................................................... 8

Disadvantages .................................................................................................................................................... 8


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1) DILATOMETER

A dilatometer test consists of pushing a flat bladelocated at the end of a series of rods. Once at the testingdepth, a circular steel membrane located on one side of

the blade is expanded horizontally into the soil. Thepressure is recorded at specific moments during the test.The blade is then advanced to the next test depth. Dr.Silvano Marchetti invented the Flat Dilatometer in 1975and was improved by Dr. Aziz Akbar

Working & Explanation

A Flat Dilatometer probe consists in a steel blade with a circular membrane in one of its sides.

The membrane has electrical sensors which can detect its position (flexed to the inside or outside andparallel to the blade).This blade is pushed into the ground and at desired depths the membrane is inflatedusing any kind of compressed gas, normally nitrogen. When the probe is pushed into the ground the soilpressure makes the membrane flex to the inside of the dilatometer blade. At measurement depths themembrane is inflated and an "A" reading of pressure is obtained when the membrane reaches its initialposition (parallel to the blade), and a "B" reading is obtained when the membrane displaces 1.1 mm tothe outside. This parameters are used in several correlations to obtain properties of the soil, such ascompressibility and soil behaviour classification. The following figure depicts a normal flat dilatometersounding.


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Improvements in Dilato-meter Dilato-meter was improved by Dr. Aziz Akbar. SDMT had a rubber membrane which could be damaged if gravels are encountered while

expansion. SDMT was suitable for soft soils only. Dr. Aziz Akbar replaced the rubber membrane by a metallic piston. This rigid piston is operated

on the basis of magnetic flux. This improved form of dilato-meter gives satisfactory results for clays, silts as well as gravels. ANDMT can directly measure in-situ soil characteristics such as strength, stiffness and

deformation. The limit for the value of displacement is 1.1 mm.

Soils Parameters

THE DMT determines these soil parameters:

Tangent modulus Lateral stress Pre consolidation stress Water table and pressure (sands) Soil stratigraphy Un drained shear strength (clays) Drained friction angle (sands) Youngs Modulus Quick settlement calculations Compaction control

P-y curves for laterally loaded piles The in-situ stiffness Strength Stress history parameters of soil for better site characterization, reducing overall project cost and

improving design reliability. It also gives the engineer nearly continuous depth-profiles of these important soil properties.

Both researchers and practitioners have complemented the accuracy and breadth of theDilatometer, now in wide spread use throughout the world.

Advantages Yields in a short time a large volume of test data, working from either an SPT or CPT rig.

Test results presented in familiar parameters for easy presentation to client. Substitute for "undisturbed" sampling and testing. The DMT is quicker, less expensive, andprovides depth profile of tests.

Nearly continuous profiles of the soil parameters for design (especially settlement calculations!). Reduce lab testing delays and eliminate concerns about operator-induced error. Direct measurement of settlement and strength parameters.

Disadvantages No Sample Is recovered. Blade penetration effects the strength , stiffness.

Results of DMT are affected if the blade dirts out from the vertical during penetration.

Marchett

Akbars


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2) PRESSEUR METERDeveloped by Maynard in 1956. The pressure meter

test is an in-situ testing method which is commonly used toachieve a quick and easy measure of the in-situ stress-strainrelationship of the soil which provides parameters such asthe elastic modulus. The pressuremeter test is an in-situtesting method used to achieve a quick measure of the in-situ stress-strain relationship of the soil. In principle, thepressuremeter test is performed by applying pressure to thesidewalls of a borehole and observing the correspondingdeformation. ASTM D4719The pressuremeter consists of two parts, the read-out unit

which rests on the ground surface, and the probe that isinserted into the borehole (ground). The original Mnard-type pressuremeter was designed to belowered into a performed hole and toapply uniform pressure to the boreholewalls by means of inflatable flexiblemembrane. As the pressure increases, theborehole walls deform. The pressure isheld constant for a given period and the

increase in volume required formaintaining the constant pressure isrecorded. A load-deformation diagram andsoil characteristics can be deduced bymeasurement of the applied pressure andchange in the volume of the expandingmembrane.

Types of Pressure meters

Maynard Pressure meter Self Boring Pressure meter Skew boring Pressure meter

The major difference between categories of pressuremeter lies in the method f installationof the instrument into the ground. Three main types of pressuremeters are:

The borehole pressuremeter: The instrument is inserted into a performed hole. The self-boring pressuremeter: The instrument is self-bored into the ground with the

purpose of minimizing the sol disturbance caused by insertion.

Displacement pressuremeters: The instrument is pushed into the ground from base of aborehole. The soil displaced by the probe during insertion enters the body of instrument,reducing the disturbance to the surrounding soil


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Parameters Obtained Lift of Pressure Yield of Pressure Limit Pressure

Advantages Allows assessment of in-situ horizontal stress. Allows direct measurement of shear stiffness and un drained Strength. Well conditions boundary conditions.

Disadvantages Not very cheap. Operators need to be skilled. An appreciable amount of data processing is required.

3) STANDARD PENETROMETERThe Standard Penetration test (SPT) is a common in situ testing method used to determine

the geotechnical engineering properties of subsurface soils. It is a simple and inexpensive test toestimate the relative density of soils and approximate shear strength parameters.

Most Frequently used and cheapest of all available tests. Developed in 1927 and standardised in 1958 ASTM D1586

Description and test procedure

Standard Penetration Test, SPT, involvesdriving a standard thick-walled sample tube into theground at the bottom of a borehole by blows from aslide hammer with standard weight and fallingdistance. The sample tube is driven 150 mm into theground and then the number of blows needed for thetube to penetrate each 150 mm (6 in) up to a depthof 450 mm (18 in) is recorded. The sum of thenumber of blows required for the second and third 6

in. of penetration is reported as SPT blow countvalue, commonly termed "standard penetrationresistance" or the "N-value".

The N-value provides an indication of therelative density of the subsurface soil, and it is usedin empirical geotechnical correlation to estimate theapproximate shear strength properties of the soils.

Advantages Quick and simple to perform. Equipment &Expertise easily available.


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Can penetrate into the dense layers, gravel and fill. Provides a representative sample.

Disadvantages Does not provide continuous data (5ft interval). Limited applicability to cohesive soils, gravels, boulders, cobbles. A number of corrections have to be applied to get a standard value.


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4) CONE PENETROMETER The CPT test has

become one of the mostcommon and economicalmethods of subsurfaceexploration. The conepenetrometer is pushed intothe ground at a standardvelocity of 2 cm/s and data isrecorded at regular intervals(typically 2 or 5 cm) duringpenetration. The resultsprovide excellentstratigraphic detail andrepeatability provided propercare has been taken incalibration of the equipment(transducers and electronics).The cone penetrometer isinstrumented to record anumber of differentparameters, with the mostcommon being the force of the tip, the force of thesleeve, and the pore pressure behind the tip. Cone penetrometers have also been used to provideor measure electrical properties, shear wave velocities, visual images of the soil, acoustic

emissions, temperature, and water samples. Developed in Netherlands so also called as Dutch Cone Test (DCT) ASTM D3441 , ASTM D 5778

Types of Cone penetration Tests Mechanical CPT Electrical CPT Piezo Cone Electric Piezo/Friction

Seismic Cone

Parameters Obtained Cone End Resistance qc Sleeve Resistance qf Friction Ratio Fr

Advantages Test can be performed on wide range of soil types. .It provides a continuous or near continuous data.

Disadvantages Does not provide any soil samples. It cannot penetrate into very dense soils or soils containing boulders and cobles.

types of penetrometers..(ubaid ahmed mughal)

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