Geotechnical Engineering Properties of Soils Tests

Geotechnical plan Properties of Soils examensJump toAdvant senesces and Disadvantages of SPT Standard incursion TestAdvantages and Disadvantages of Cone cleverness TestAdvantages and Disadvantages of Shear Vane TestAdvantages and Disadvantages of wash away BoringAdvantages and Disadvantages of Percussion put up BoringAdvantages and Disadvantages of Rotary Auger BoringDuring the SPT, it was achievable to take disturbed and undisturbed consumes using split barrel- stressr which were employ for further riddleing set up hears. The in situ penetration mental test provides a malicious gossip sample for identification purposes and for the laboratory tests that allow the use of disturbed samples. The order acting of sampling soil consists of thrust a split-barrel sampler to obtain a representative, disturbed sample and to concurrently obtain a measure of the impedance of the subsoil to the penetration of a standard sampler. The test is conducted inside a borehole. A spli t smooch sampler is given up to the back end of a core barrel and move into position at the fundament of the borehole. The sampler is driven into the ground by a drop hammer weighing 68 kg stemmaing through a height of 76 cm. The exit of hammer blows is counted. The number required to drive the sampler three successive 150mm ontogenys is recorded. The first increment (0-150mm) is non included in the N value as it is anticipate that the top of the test bea has been disturbed by the class perioding 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 air-tight container for inspection and description.Advantages and Disadvantages of SPT Standard Penetration TestADVANTAGESRelatively quick and round-eyed to performAble to penetrate dense layers, gravel, and fillEquipm ent and expertise for the test is widely availableIn addition to overburden pressure and intercourse density the SPT N-value is excessively a function of soil persona, particle coat, and age and stress history of the depositProvides a representative soil sampleProvides useful index of relative vividness and compressibility of the soilDISADVANTAGESThe SPT does not typically provide continuous data, therefore important data such as weak seams whitethorn be missedSomewhat sulky than other sample orders due to sample retrievalThe basic problems to visit are change in effective stress at the bottom of the borehole, dynamic energy reaching the sampler, sampler design, interval of impact, penetration resistance count.Samples that are obtained from the SPT are disturbed.Cone Penetration Test (CPT)What is CPT?Cone Penetration Tests are conducted to obtain the conoid shape resistance, the side attrition and, if there is a piezocone, the pore pressure. The soil type substructure be determined by analysing these result the values dope also be used in the design of shallow foundations through the estimation of stiffness and shear effectiveness 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 fifties at the Dutch Laboratory for Soil Mechanics in Delft to ask 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. edgeCPT is static penetration test in which the craft 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 weapon remains. 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 dee p. The fight 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 potpourri testament be based on ratio of tip and sleeve resistance. The tip resistance will be high in backbone and low in clays duration the sleeve friction will be low in sands and high in clays.Advantages and Disadvantages of Cone Penetration TestADVANTAGEContinuous dataReliable, repeatable test resultsDISADVANTAGESunfitness to penetrate through gravels and cobblesElimination of operator errorLess populate database than SPT due to the new technologyLack of samplingSHEAR weather weathervane TESTWhat is Shear Vane Test?The vane shear test is an in-situ geotechnical exam methods used to number the undrained shear strength of in full saturated clays without disturbance. The test is relatively simple, quick, and provides a cost-effective right smart of estimating the soil shear strength therefore, it is widely used in geotechnical investigations. nether special condition, the vane shear test can be also carried out in the laboratory on undisturbed soil specimens up to now the use of the vane shear test in in-situ testing is much more common.ProcessThe 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 harmless 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 wax 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 wisdom of least three times the borehole diameter lower that the borehole bottom in order to avoid the borehole disturbance effects. The test perishs by displace the vane and the rod vertically into the soft soil. The vane is then revolved at a slow rate of 6 to 12 per minute. The tortuousness is measured at regular time intervals and the test continues until a level best 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 rotary motion 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 relative to the applied torque and the dimensions of the vane.Advantages and Disadvantages of Shear Vane TestADVANTAGESRapid and frugal testReproducible results in homogeneous soilsInexpensive method for standard clay sensitivityDISADVANTAGESLimited to soft to stiff cohesive soils product line vane shear strength must be correctedResults can be affected by anisotropic soils, sand lenses, shells, and seams oil production break BORINGWhat is Wash Boring?A popular method to drill larger size holes in soft formations. Casing with a showcase crown attached is rotated into the ground and wet is used to ladened out the drilled formation. It is one of a boring system by which material make relaxedned by a dapple is borne to the surface in the annular space between the bit and casing by water constrained down through the pipe bearing the bitProcessFor test boring over 3 meter in depth, this method can be conveniently used. In this method a fix steel pipe known as casing pipe or drive pipe is driven into the ground for a certain depth. thence a pipe usually known as water spring pipe or wash pipe, which is shorter in diameter, is lowered into t he 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. pee under considerable pressure is forced down the wash pipe. The hydraulic pressure displaces the material immediately down the stairs the pipe and the slurry and so formed is forced up through the annular space between the deuce 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. until now the change of stratification can be guessed from the rate of progress of campaign the casing pipe as well as the color of slurry silklike out. Yet the results obtained by wash boring process give plum good information about the nature of the sub-soil strata. This method can be adopted in soft to stiff cohesive soils and fine sand.Advantages and Disadvantages of Wash BoringADVANTAGES undersurface be used in difficult terrain diminished equipment costUsed in uncased holesDISADVANTAGESDepth limited to about 30m barrier in obtaining accurate location of groundwater level.Undisturbed soil samples cannot be obtained.rhythm section RIG BORINGWhat is Percussion Rig Boring?Percussion carpeting Boring is widely used in UK. Percussion bore 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.ProcessThis method consists of breaking up of the sub-strata by repeated blows from a bit or chisel. Percussion methods start by inflame up the tool assembly by the pull 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 leans and soils having boulders. In general, a mould used to drill holes is called a drill rig generally spring driven, but may be hand driven. A winch is provided to raise and lower the drilling tools into the hole.Advantages and Disadvantages of Percussion Rig BoringADVANTAGESSimple to be given and maintainSuitable for a wide variety of rocksOperation is possible above and beneath the water-tableIt is possible to drill to considerable depthsDISADVANTAGESSlow, compared with other methodsEquipmen t can be heavyProblems can occur with unstable rock formationsWater is needed for dry holes to help remove cuttingsROTARY AUGER BORINGWhat 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 firmly ground conditions. This type of boring machine can be also use for stiltbird works. It can bore the hole up to depth of 50 m and diameter of 300 mm to 2 m.ProcessWhen 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 gingersnap 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 low-toned diameter are needed, diamond bit is preferred. There are two main type of rotary auger boring which are lay AugerConsists 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 AugerShort courseSimple flightContinuous flightAdvantages and Disadvantages of Rotary Auger BoringADVANTAGE ardentDrill through any type of soil or rockCan drill to depths of 50 mUndisturbed samples can be easily recoveredDISADVANTAGEExpensive equipmentTerrain must be cordial to motorized vehicleDifficulty in obtaining location of groundwater level special time requir ed for set-up and clean-up