What Is The Standard Penetration Tests Engineering Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

The Standard Penetration Tests aims to determine the SPT 'N' value, which gives an indication of the soil stiffness and can be empirically related to many engineering properties. The purpose of the Standard Penetration Test is to identify the soil stratification and engineering properties of soil layers.

Process

During the SPT, it was possible to take disturbed and undisturbed samples using split barrel-sampler which were used for further laboratory tests. The in situ penetration test provides a soil sample for identification purposes and for the laboratory tests that allow the use of disturbed samples. The method of sampling soil consists of driving a split-barrel sampler to obtain a representative, disturbed sample and to simultaneously obtain a measure of the resistance of the subsoil to the penetration of a standard sampler. The test is conducted inside a borehole. A 'split spoon' sampler is attached to the bottom of a core barrel and lowered into position at the bottom of the borehole. The sampler is driven into the ground by a drop hammer weighing 68 kg falling through a height of 76 cm. The number of hammer blows is counted. The number required to drive the sampler three successive 150mm increments is recorded. The first increment (0-150mm) is not included in the N value as it is assumed that the top of the test area has been disturbed by the drilling process. The SPT N is the number of blows required to achieve penetration from 150-450mm. The hammer weight, drop height, spoon diameter, rope diameter etc. are standard dimensions. After the test, the sample remaining inside the split spoon is preserved in an airtight container for inspection and description.

Advantage and Disadvantage

DISADVANTAGE

Relatively quick and simple to perform

The SPT does not typically provide continuous data, therefore important data such as weak seams may be missed

Able to penetrate dense layers, gravel, and fill

Somewhat slower than other sample methods due to sample retrieval

Equipment and expertise for the test is widely available

In addition to overburden pressure and relative density the SPT N-value is also a function of soil type, particle size, and age and stress history of the deposit

Provides a representative soil sample

The basic problems to consider are change in effective stress at the bottom of the borehole, dynamic energy reaching the sampler, sampler design, interval of impact, penetration resistance count.

Provides useful index of relative strength and compressibility of the soil

Samples that are obtained from the SPT are disturbed.

CONE PENETRATION TEST (CPT)

What is CPT?

Cone Penetration Tests are conducted to obtain the cone resistance, the side friction and, if there is a piezocone, the pore pressure. The soil type can be determined by analysing these result the values can also be used in the design of shallow foundations through the estimation of stiffness and shear strength of cohesive soils. The cone penetration test (CPT) is a method used to determine the geotechnical engineering properties of soils and delineating soil stratigraphy. It was initially developed in the 1950s at the Dutch Laboratory for Soil Mechanics in Delft to investigate soft soils. Based on this history it has also been called the "Dutch cone test". Today, the CPT is one of the most used and accepted in soil methods for soil investigation worldwide.

http://geosystems.ce.gatech.edu/Faculty/Mayne/Research/devices/cpt.gif

Process

CPT is static penetration test in which the device is pushed rather than then driven by blows into the soil. The CPT consist of cone which been attached to a rod that been protected by an outer sleeve. A 60o cone with face area 10cm2 and 150cm2 of friction sleeve is hydraulically pushed into the ground at a constant speed ranging from 1.5 to 2.5 cm/s about 80mm deep. The force required maintaining this penetration rate, and the shear force acting on the friction sleeve is recorded. The friction ratio gives an indication of the soil type. The CPT Soil Classification will be based on ratio of tip and sleeve resistance. The tip resistance will be high in sand and low in clays while the sleeve friction will be low in sands and high in clays.

Advantage and Disadvantage

ADVANTAGE

DISADVANTAGE

Continuous data

Inability to penetrate through gravels and cobbles

Elimination of operator error

Less populated database than SPT due to the new technology

Reliable, repeatable test results

Lack of sampling

SHEAR VANE TEST

What is Shear Vane Test?

The vane shear test is an in-situ geotechnical testing methods used to estimate the undrained shear strength of fully saturated clays without disturbance. The test is relatively simple, quick, and provides a cost-effective way of estimating the soil shear strength; therefore, it is widely used in geotechnical investigations. Under special condition, the vane shear test can be also carried out in the laboratory on undisturbed soil specimens however the use of the vane shear test in in-situ testing is much more common.

vanetoggle.jpg (29984 bytes)

Process

The vane shear test is an in-situ geotechnical testing methods used to estimate the undrained shear strength of fully saturated clays without disturbance. The results of the test are not reliable if clay contains silt or sand. The vane shear test apparatus consists of a four-blade stainless steel vane attached to a steel rod that will be pushed into the ground. For a weak soils which has Cu less than 50 kPa, the size of the blade is 75mm wide x 150 mm long while for the slightly strong soils which has Cu between 50 kPa to 100 kPa, 50 x 100 mm blade should be use. The height of vane is usually twice its overall widths and is often equal to 10 cm or 15 cm. 

The test can be conducted either from the ground surface or from the bottom of a borehole or a test pit. If conducted from the bottom of a borehole, the test area should be should be at the depth of least three times the borehole diameter lower that the borehole bottom in order to avoid the borehole disturbance effects. The test starts by pushing the vane and the rod vertically into the soft soil. The vane is then rotated at a slow rate of 6° to 12° per minute. The torque is measured at regular time intervals and the test continues until a maximum torque is reached and the vane rotates rapidly for several revolutions. At this time, the soil fails in shear on a cylindrical surface around the vane. The rotation is usually continued after shearing and the torque is measured to estimate the remoulded shear strength. The undrained shear strength of the saturated soil is proportional to the applied torque and the dimensions of the vane.

Advantage and Disadvantage

ADVANTAGE

DISADVANTAGE

Rapid and economical test

Limited to soft to stiff cohesive soils

Reproducible results in

homogeneous soils

Field vane shear strength must be

corrected

Inexpensive method for measuring

clay sensitivity

Results can be affected by

anisotropic soils, sand lenses,

shells, and seams

4.0 BORING

WASH BORING

What is Wash Boring?

A popular method to drill larger size holes in soft formations. Casing with a casing crown attached is rotated into the ground and water is used to flush out the drilled formation. It is one of a boring system by which material loosened by a bit is borne to the surface in the annular space between the bit and casing by water forced down through the pipe bearing the bit

http://www.denichsoiltest.com/wp-content/uploads/2010/12/washboring-rig.png

Process

For test boring over 3 meter in depth, this method can be conveniently used. In this method a hollow steel pipe known as casing pipe or drive pipe is driven into the ground for a certain depth. Then a pipe usually known as water jet pipe or wash pipe, which is shorter in diameter, is lowered into the casing pipe. At its upper end, the wash pipe is connected to water supply system while the lower end of the pipe is contracted so as to produce jet action.

Water under considerable pressure is forced down the wash pipe. The hydraulic pressure displaces the material immediately below the pipe and the slurry thus formed is forced up through the annular space between the two pipes. The slurry is collected and samples of material encountered are obtained by settlement. In this process the particles of finer material like clay, loam etc. do not settle easily and the larger and heavy particles of the soil may not be brought up at all.

Moreover, the exact position of a material in the formation cannot be easily be located. However the change of stratification can be guessed from the rate of progress of driving the casing pipe as well as the color of slurry flowing out. Yet the results obtained by wash boring process give fairly good information about the nature of the sub-soil strata. This method can be adopted in soft to stiff cohesive soils and fine sand.

Advantage and Disadvantage

ADVANTAGE

DISADVANATAGE

Can be used in difficult terrain

Depth limited to about 30m

Low equipment cost

Difficulty in obtaining accurate location of groundwater level.

Used in uncased holes

Undisturbed soil samples cannot be obtained.

PERCUSSION RIG BORING

What is Percussion Rig Boring?

Percussion Rug Boring is widely used in UK. Percussion drilling method of advancing a boring is of common use in drilling water wells. This method consists of breaking up of the sub-strata by repeated blows from a bit or chisel. This type of boring can make a borehole up to 150 mm - 300 mm diameter and depth up to 50 - 60 m. However this method is not recommended for loose sand or clayey soils.

http://www.globalsecurity.org/military/library/policy/army/fm/5-484/fig9-2.gif

Process

This method consists of breaking up of the sub-strata by repeated blows from a bit or chisel. Percussion methods start by raise up the tool assembly by the winch to 1 m above the bottom of the hole. It allows the tool assembly to fall under its own weight to drive the cutting tools into the soil. The material thus pulverized is converted into slurry by pouring water in the bore. At intervals the slurry is bailed out of the hole and dried for examination.

The slurry will be removed by bailers or pump. After that, tool will be raise to surface when the cutting tools are full of soil to obtain undisturbed sample. This method can be adopted in rocks and soils having boulders. In general, a machine used to drill holes is called a drill rig generally power driven, but may be hand driven. A winch is provided to raise and lower the drilling tools into the hole.

Advantage and Disadvantage

ADVANTAGE

DISADVANTAGE

Simple to operate and maintain

Slow, compared with other methods

Suitable for a wide variety of rocks

Equipment can be heavy

Operation is possible above and below the water-table

Problems can occur with unstable rock formations

It is possible to drill to considerable depths

Water is needed for dry holes to help remove cuttings

ROTARY AUGER BORING

What is Rotary Auger Boring?

A drill bit is pushed by weight of drilling equipment and rotated by a motor. This drilling method with mud pump for flushing can be direct circulation and reverse circulation, with tricone bit and drag bit Nevertheless, the torque is relatively critical for this drilling method. It is widely used in soft to medium hard ground conditions. This type of boring machine can be also use for piling works. It can bore the hole up to depth of 50 m and diameter of 300 mm to 2 m.

http://3.bp.blogspot.com/-TauofjmHi3c/UE6pCzo9ROI/AAAAAAAAAo8/7RPeYxK9eR0/s1600/05.gif

Process

When rocks or hard pans are to be penetrated for examination, core drilling is done to get undisturbed samples of the formation. In this process a hole is made by rotating a hollow steel tube having a cutting bit at its base. The cutting bit makes an annular cut in the strata and leaves a cylindrical core of the material in the hollow tube. Two types of cutting bits are generally used, namely, diamond bit and shot bit. Diamond bit consists of industrial diamonds set in the face of the bit and in shot bit, chilled shot is used as an abrasive to cut the hard pan. When core samples of small diameter are needed, diamond bit is preferred. There are two main type of rotary auger boring which are:

Bucket Auger

Consists of an open‐top metal cylinder with cutter mounted on a baseplate as the soil is cut, it passes into the bucket, which is then raised and emptied at intervals.

Can be used in frim soil.

Not suitable for cohesionless soil below water table.

Flight Auger

Short flight

Simple flight

Continuous flight

Advantage and Disadvantage

ADVANTAGE

DISADVANTAGE

Quick

Expensive equipment

Drill through any type of soil or rock

Terrain must be accessible to motorized vehicle

Can drill to depths of 50 m

Difficulty in obtaining location of groundwater level

Undisturbed samples can be easily recovered

Additional time required for set-up and clean-up

5.0 GEOPHYSICAL SURVEY

Geophysical methods provide information about the physical properties of the earth's subsurface. Geophysical surveys are non-destructive methods for investigating the subsurface soil, rock, and groundwater, without digging, probing, or drilling. Geophysical surveys can be used to locate many types of buried objects. Underground storage tanks (USTs), buried drums, underground utilities, subsurface foundations, rebar in concrete, or other buried objects can be located using geophysical surveys. Soil or ground water contamination, sinkholes, and other subsidence features can also be investigated using surface and downhole geophysical surveys. There are two general types of methods which are active, which measure the subsurface response to electromagnetic, electrical, and seismic energy and passive, which measure the earth's ambient magnetic, electrical, and gravitational fields.

METHOD

MEASURED PARAMETER

OPERATIVE PHYSICAL PROPERTIES

Seismic

Travel times of reflected/refracted seismic waves

Density and elastic moduli, which determine the propagation velocity of seismic waves

Gravity

Spatial variations in the strength of the gravitational field of the earth

Density

Magnetic

Spatial variations in the strength of the geomagnetic field

Magnetic susceptibility and remanence

Electrical Resistivity

Earth resistance

Electrical conductivity

Induce Polarization

Polarization voltages or frequency-dependent ground resistance

Electrical capacitance

Self-Potential

Electric potentials

Electrical conductivity

Electromagnetic

Response to electromagnetic radiation

Electrical conductivity and inductance

Radar

Travel times of reflected radar pulses

Dielectric constant

5.1 Seismic

Seismic measurement involves the measurement of seismic waves traveling through the subsurface. There are three method of seismic that has been commonly used for shallow applications include refraction, reflection and surface wave analysis (MASW).

METHOD

APPLICATIONS

ADVANTAGE

DISADVANTAGE

Seismic Refraction

To determine the depth of bedrock and thickness of geologic strata, structure and identifying anomalous conditions.

Can provide data up to 100 feet or more.

Can show up to 2 or 3 layers.

Sensitive to noise and vibrations.

Will not detect thin layers.

Seismic Reflection

Can be used to determine the depth and thickness of geological strata and detect any changes of lateral and locate anomalous geological conditions.

Provide high resolution of cross-section

Depth range as shallow as 30 feet and can be more than 1000 feet.

Sensitive to noise and vibrations.

Slower production rate than mast geophysical methods.

Multichannel Analysis of Surface Waves (MASW)

Can determine the depth, thickness of strata layers, soil and rock elastic properties.

Can provide cross-section of shear wave velocity along a profile line.

Maximum depth limited to approximately 80 feet in typical conditions.

5.2 Electrical Resistivity

Electrical resistivity measurements are made by placing four electrodes in contact with the soil or rock (ASTM D6431-99). A current is caused to flow in the earth between one pair electrodes while the voltage across the other pair of electrodes is measured. The depth of measurements is related to the electrode spacing. The resistivity measurement represents the apparent resistivity averaged over a volume of the earth determined by the soil, rock, and pore fluid resistivity, along with the electrode geometry and spacing.

METHOD

APPLICATIONS

ADVANTAGE

DISADVANTAGE

Electrical Resistivity Imaging (ERI)

Can be used to determine the depth and thickness of geological strata and detect any changes of lateral and locate anomalous geological conditions. Locate also buried wastes

Good vertical resolution.

Depth range up to 200 feet.

Effectiveness decrease at very low resistivity.

Interference from nearby metal pipes, cable or any other material that have influence on magnetic field

Capacitively - coupled Resistivity Measurements

Can be used to determine the depth and thickness of geological strata and detect any changes of lateral and locate anomalous geological conditions.

Used without electrodes.

Data acquired continuously.

Will works in high resistivity area only

Maximum depth of 30 feet.

Induced Polarization Measurements (IP)

Used commonly for mineral exploration and also can detect lateral subsurface changes in 2-D and located buried wastes

Can be used to measure up to 200 feet or more.

Will responds to certain types of non-metallic debris.

Very sensitive to external electrical noise.

Interference from nearby metal pipes, cable or any other material that have influence on magnetic field

Spontaneous Potential

Use to determine the seepage from dams, locate the fracture flow, caves and recharge zones

Easy to make measurement.

Time series management can be used to monitor any changes in seepage.

Need intrusive contact with the ground.

Nonpolarizing electrodes must be used.

Interference from cathodic protection, natural Earth currents and cultural features.

5.3 Electromagnetics

Electromagnetic methods provide a means to measure subsurface electrical conductivity and to identify subsurface metal objects. Electrical conductivity is a function of soil and rock type, porosity and permeability, as well as the composition of fluids that fill the pore spaces (McNeill, 1980 and McNeill and Bosnar, 1986). Conductivity values may be related to groundwater properties such as specific conductance or total dissolved solids.

METHOD

APPLICATIONS

ADVANTAGE

DISADVANTAGE

Frequency Domain Electromagnetic

Primarily used of profiling to detect and map lateral change in natural geologic and hydrologic conditions. Also can detect any other metal material buried in the ground.

Easy to make the measurement.

Does not needed ground contact.

Can provide measurement up to 200 feet.

Limited vertical resolution.

Interference from nearby metal pipes, cable or any other material that have influence on magnetic field.

Time Domain Electromagnetic (TDEM)

Primarily used to determine the depth and thickness of natural geologic and hydrologic conditions. Can also detect and maping of leachate plumes from landfill.

Good lateral and vertical resolution.

Depth range from 20 to nearly 3000 feet

Require a large transmitter coil if the measurement is deep.

Interference from nearby metal pipes, cable or any other material that have influence on magnetic field.

Very Low Frequency Measurement (VLF)

Primarily used for location and mapping of near vertical contacts, fractures and faults containing minerals, clay or water

Measurement are easily and rapidly

Can provide relatively deep measurements

Station measurements only.

In horizontal layers of soil and rock with very fractures, this method does not well function

REFFERENCE

Akhtar-Schuster, M., Kirk, M., Gerstengarbe, F.-W., and Werner, P. C. 2000. Causes

and impacts of the declining resources in the Eastern Sahel. Desertification Control Bulletin 36:42-49.

Garcia Latorre, J., Sanchez Picon, A. and Garcia Latorre, J. 2001. The man-made

desert: effects of economic and demographic growth on the ecosystems of arid southeastern Spain. Environmental History 6:75-94.

Holzel, N., Haub, C., Ingelfinger, M. P., Otte, A., and Pilipenko, V. N. 2002. The return of

the steppe - large-scale restoration of degraded land in southern Russia during the post-Soviet era. Journal for Nature Conservation 10:75-85.

Saiko, T. A. and Zonn, I. S. 2000. Irrigation expansion and dynamics of desertification in

the Circum-Aral region of central Asia. Applied Geography 20:349-367.

UNCCD 1995. Down to Earth: A simplified guide to the Convention to Combat

Desertification, why it is necessary and what is important and different about it. Bonn, Germany: Secretariat for the United Nations Convention to Combat Desertification. (see also Facts Sheet, FAQ and Explanatory Leaflet at http://www.unccd.int/knowledge/menu.php

Juo, A. S. R. and Wilding, L. P. 2001. Land and civilization: an historic perspective. Pp.

13-19 in Bridges, E. M., Hannam, I. D., Oldeman L. R., Penning de Vries, F. W. T., Scherr, S.J. and Sombatpanit, S. 2001. Response to Land Degradation. Enfield, New Hampshire, USA: Science Publishers.

Deforestation (n.d.) Retrieved November 19, 2012, from

http://www.botany.uwc.ac.za/envfacts/facts/deforestation.htm

Global Deforestation (n.d.) Retrieved November 19, 2012, from

http://www.globalchange.umich.edu/globalchange2/current/lectures/deforest/deforest.html

Case Study of Indonesia (n.d.) Retrieved November 19, 2012, from

http://deforestationproject.webs.com/casestudyofindonesia.htm

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.