How to Read a Spt Boring Log

Dynamic Compaction and Dynamic Surcharging at Dubai's Palm Jumeira Sewage Treatment Plants

Babak Hamidi , Serge Varaksin , in Footing Comeback Case Histories, 2015

Site-specific geotechnical investigation

4 SPT boreholes (BH-one to BH-4) were drilled, and tested in the center and three sides of Lot A-A's tank. These boreholes as well indicated that the upper 3   k of sand was very dense, simply the soil then became very loose to medium dense at groundwater level. SPT blow counts at depths of 3–eight   m varied from equally low as iv to as high as 14. Northward values and then vicious within the range of 11–20 downwardly to depths of approximately 12–13   m, where the ground became very dense and N exceeded 50. Fines content of the 38 samples that were extracted from the four boreholes ranged from 16 and 21%, which was greater than the 2–ten% range that was indicated by the preliminary geotechnical investigation. Also, although no silt pockets were identified nether the tank, as fines content was observed to exist more 20% in almost half of the samples and equally loftier as 30%, it was understood that the tank's location was probably ane of the siltiest areas of the reclamation.

SPT accident counts and fines content in the preliminary and supplementary boreholes are shown in Fig. 10.seven. Comparison of these results shows that while soil forcefulness down to depths of approximately 8   g was very like in the preliminary and site-specific SPT boreholes, the thickness of the loose to medium dumbo sand layer was greater in the latter tests. It can also be seen that the actual fines content of the soil was noticeably greater than what could have been conceived from the preliminary geotechnical investigation report.

Figure x.7. SPT blow counts and fines content in the preliminary and site-specific boreholes before ground improvement.

Two PMTs were besides carried out in the tank area. As information technology was already established that the ground was very dense above water table level, testing was done at 1   grand intervals below bounding main level. These tests also reconfirmed that the submerged soil was in a loose country. In this zone, PMT limit pressure level, P_LM , was less than 100   kPa to about 700   kPa, and Menard modulus, E_G , was measured to be from less than 1–half-dozen   MPa. P_LM and East_Yard before ground improvement are shown in Fig. 10.8.

Figure x.eight. PMT limit pressure level and modulus before basis improvement.

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Soil Investigation and Pile Design

Mohamed A. El-Reedy PhD , in Onshore Structural Design Calculations, 2017

8.2.4 Standard Penetration Test

The standard penetration examination (SPT) is a well-established and unsophisticated method which was developed in the United States c.1925. It has since undergone refinements with respect to equipment and testing procedure. The testing procedure varies in different parts of the world.

Therefore, standardization of SPT was essential in club to facilitate the comparison of results from dissimilar investigations. The equipment is uncomplicated, rugged, and relatively cheap. Some other advantage is that representative soil samples are obtained, though they are disturbed.

The reliability of the method and the accurateness of the result depend largely on the experience and care of the engineer on site.

A split-barrel sampler is driven from the lesser of a prebored hole into the soil by means of a 63.v-kg hammer, dropped freely from a acme of 0.76   m. The diameter of the prebored pigsty commonly varies between threescore and 200   mm. If the hole does not stay open by itself, casing or drilling mud should be used. The sampler is first driven to a depth of xv   cm beneath the lesser of the prebored hole, then the number of blows required to bulldoze the sampler another 30   cm into the soil, the so-called N30 count, is recorded. The rods used for driving the sampler should have sufficient stiffness. Normally, when sampling is carried out to depths greater than around 15   m, 54   mm rods are used.

The quality of test results depends on several factors, including the actual energy delivered to the head of the drill rod, the dynamic backdrop (impedance) of the drill rod, the method of drilling, and borehole stabilization. The actual energy delivered can vary between l% and 80% of the theoretical complimentary-autumn free energy. Therefore, correction factors for rod free energy (60%) are usually used, according to Seed and De Alba (1986). The SPT can exist difficult to perform in loose sands and silts beneath the groundwater level (typical for country reclamation projects), equally the borehole tin plummet and disturb the soil to exist tested. The following factors can affect the test results: nature of the drilling fluid in the borehole, diameter of the borehole, the configuration of the sampling spoon, and the frequency of delivery of the hammer blows.

Therefore, it should be noted that drilling and stabilization of the borehole must exist carried out with intendance. The equipment of the test is shown in Fig. eight.2. The measured Northward-value (blows/0.3   m) is the so-chosen standard penetration resistance of the soil. The penetration resistance is influenced by the stress conditions at the depth of the exam. Peck et al. (1996) proposed, based on settlement observations of footings, the post-obit relationship for correction of solitude pressure: the measured North-value is to be multiplied by a correction factor CN to obtain the reference value N ₁, respective to an constructive overburden stress of 1   t/ft^two (approximately 107   kPa).

Figure 8.2. Sketch for CPT.

(eight.1) $N_1=N\cdot \mathrm{CN}$

where CN is a stress correction cistron and p′ is the effective vertical overburden pressure level.

(8.2) $\mathrm{CN}=0.77{\log }_{10}\left(\frac{20}{p\prime }\right)$

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Geotechnical parameters from CPT records

Abolfazl Eslami , ... Mohammad Chiliad. Eslami , in Piezocone and Cone Penetration Test (CPTu and CPT) Applications in Foundation Engineering, 2020

4.ten CPT correlations with SPT

The simplicity and common usage of SPT around the world and the accuracy and continuity of CPT led the researchers to correlate the results of these ii tests to be used in geotechnical designs. Relationship between CPT and SPT is more often than not specified by q_c /N _SPT ratio (q_c : cone tip resistance; Northward _SPT : SPT accident counts). The human relationship between q_c /Due north _SPT ratio along mean grain size of soil particle D _fifty (mm) in power form as Eq. (4.24). In Eq. 4.24, a and c coefficients are constant and several researchers proposed these coefficients every bit illustrated in Fig. iv.ten. For instance, Kulhawy and Mayne (1990) equation has the coefficients c   =   five.44 and a   =   0.26.

Effigy 4.ten. The graph determining the relation betwixt q_c and Due north ₆₀ based on mean grain size of soil (D _fifty ) (Robertson and Campanella, 1983).

(4.24) ${\text{q}}_{\text{c}}/N_{SPT}={{\text{cD}}_{\mathrm{fifty}}}^{\text{a}}$

To use the to a higher place figure, the median grain size (D ₅₀ ) evaluation from grain size distribution test is necessary. Lunne et al. (1997) proposed a method for the estimation of Northward _lx values directly from CPTu results without measuring D ₅₀ . They proposed the use of Ic to correlate CPT and SPT equally the post-obit relationship.

(4.25) $\frac{qc/pa}{N_{60}}=\mathrm{eight.5}(\mathrm{one}-\frac{I_c}{\mathrm{4.vi}})$

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Seismic analysis of piles

Ruwan Rajapakse , in Pile Pattern and Construction Rules of Thumb (Second Edition), 2016

nineteen.v.half-dozen How to obtain (N ₁)_sixty

(19.5) ${({\mathrm{North}}_{\mathrm{i}})}_{\mathrm{sixty}}=N_m\times C_{\text{North}}\times C_{\text{Due east}}\times C_{\text{B}}\times C_{\text{R}}$

•

N _g , SPT value measured in the field.

•

C _{Due north}, overburden correction factor = (P _a /σ′)^0.5 P _a  = 100 kPa; σ′, effective stress of soil at point of measurement.

•

C _E, energy correction factor for the SPT hammer. For donut hammers C _E = 0.5–1.0; for trip type donut hammers; C _East = 0.eight–1.3.

•

C _B, borehole diameter correction. For borehole diameters 65–115 mm employ C _B = ane.0; for borehole bore of 150 mm, utilise C _B = 1.05; for borehole diameter of 200 mm, apply C _B = 1.15.

•

C _R, rod length correction (rods attached to the SPT spoon would exert their weight on the soil. Longer rods would exert a higher load on soil and in some cases the spoon would go down due to the weight of rods without whatsoever hammer blows. Hence, correction is made to business relationship for the weight of rods).

For rod length < 3 m, use C _R = 0.75; for rod length iii–4 m, use C _R = 0.eight; for rod length 4–six m, use C _R = 0.85; for rod length vi–10 m, employ C _R = 0.95; for rod length 10–30 m, use C _R = one.0.

Design example xix.one

Consider a point at a depth of 5 m in a sandy soil (fines < 5%). Total density of soil is 1800 kg/mⁱⁱⁱ. The groundwater is at a depth of 2 m. Corrected (Due north ₁)₆₀ value is fifteen. Peak horizontal acceleration at the footing surface (a _max) was found to exist 0.15g for an earthquake of magnitude 7.five. Check to see whether the soil at a depth of 5 m would liquefy under an earthquake of vii.v magnitude.

Pace 1: find the cyclic stress ratio.

(19.six) $\text{Cyclic}\text{stress}\text{ratio}(C\mathrm{South}R)=0.65\left(\frac{a_{\max }}{g}\right)\times \left(\frac{\sigma }{{\sigma }^{\prime }}\right)\times r_{\text{d}}$

Here a _max, acme horizontal acceleration at the basis surface = 0.xvk; σ, total stress at the point of concern; σ′, constructive stress at the point of concern; r _d, stress reduction coefficient (this parameter accounts for the flexibility of the soil profile).

(19.vii) $r_{\text{d}}=\mathrm{i.0}-0.00765Z\text{for}Z<9.15\text{m}(Z\text{is}\text{depth}\text{to}\text{the}\text{point}\text{of}\text{business organisation}\text{in}\text{meters})$

(nineteen.8) $r_{\text{d}}=1.174-0.0267Z\text{for}9.15\text{m}<Z<23\text{thousand}$

$\sigma =\mathrm{five}\times 1800=9000\text{kg}/{\text{m}}^{\mathrm{ii}}$

${\sigma }^{\prime }=2\times 1800+\mathrm{iii}(1800-1000)=6000\text{kg}/{\text{m}}^2$

(Density of water = g kg/grand²)

Since the depth of concern is five thousand (which is less than 9.fifteen m) use Equation (19.7) to notice r _d.

$r_{\text{d}}=1.0-0.00765Z\text{for}Z<\mathrm{nine.fifteen}\text{chiliad};r_{\text{d}}=\mathrm{ane.0}-0.00765\times 5=0.962$

$\text{Hence,}CSR=0.65\times (0.15)\times \frac{9000}{6000}\times 0.962=\mathrm{0.1407.}$

Step 2: find the soil resistance to liquefaction.

(19.9) $CR{R}_{7.5}=\frac{1}{[34-(N_1)60]}+\frac{({\mathrm{Due\; north}}_{\mathrm{ane}})60}{135}+\frac{\mathrm{l}}{{[10\cdot {(N_1)}_{60}+45]}^2}-\frac{\mathrm{two}}{200}$

(N ₁)₆₀ value is given to be 15. Hence, CRR _seven.v = 0.155.

Since soil resistance to liquefaction (0.155) is larger than the CSR value (0.1407), the soil at v thou depth will not undergo liquefaction for an earthquake of magnitude 7.v.

Correction factor for magnitude

As yous are aware Equation (19.4) (for CRR _7.5) is valid only for earthquakes of magnitude vii.5. Correction gene is proposed to account for magnitudes dissimilar from 7.v.

(19.10) $\text{Cistron}\text{of}\text{safety}(\text{FOS})\text{is}\text{given}\text{by}=(CRR7.5/C\mathrm{Due\; south}R)$

CRR _7.v, resistance to soil liquefaction for a magnitude of 7.5 earthquake and CSR, cyclic stress ratio (which is a mensurate of the impact due to the earthquake load).

Cistron of safety for any other convulsion is given past following equation:

(nineteen.11) $\text{Gene of safety}(FOS)=\frac{CRR\mathrm{7.five}}{C\mathrm{Due\; south}R}\times M\mathrm{Due\; south}F$

MSF is magnitude-scaling factor, given in Table xix.i.

Table nineteen.1. Magnitude scaling factors

Convulsion magnitude	MSF suggested by Idris (1995)	MSF suggested by Andrus and Stokoe
five.v	ii.2	ii.viii
half-dozen.0	1.76	two.1
half-dozen.5	one.44	1.6
vii.0	one.19	i.25
vii.5	1.00	1.00
8.0	0.84
8.v	0.72

Participants of the 1985 NRC (National Research Quango) conference gave the liberty to engineers to select either of the values suggested by Idris or Andrus and Stokoe. As you tin see Idris values are more bourgeois, and in noncritical buildings, such as warehouses, the engineers may be able to use Andrus and Stokoe values.

Design example 2

CRR _vii.five value of a soil was found to be 0.11. CSR value for the soil was computed to exist 0.16. Will this soil liquefy for an earthquake of half dozen.5 magnitude?

Step 1: Find the factor of safety.

Factor of safety (FOS) = (CRR _7.5 /CSR) × MSF

MSF for an earthquake of 6.5 = i.44 (Idris)

Factor of safety = (0.11/0.16) × ane.44 = 0.99 (soil would liquefy).

Use MSF given by Andrus and Stokoe.

Factor of safety = (0.11/0.16) × i.6 = ane.1 (soil would non liquefy).

Correction factor for content of fines

Equation (19.iv) was developed for clean sand with fines content less than 5%. Correction factor is suggested for soils with higher fines contents.

(nineteen.12) $CR{R}_{\mathrm{7.v}}=\frac{1}{[34-(N_{\mathrm{one}})60]}+\frac{({\mathrm{Northward}}_{\mathrm{i}})60}{135}+\frac{\mathrm{l}}{{[\mathrm{x.}{(N_1)}_{\mathrm{lx}}+45]}^2}-\frac{2}{200}$

Corrected (N ₁)₆₀ value should be used in the aforementioned equation for soils with college fines content.

The following procedure should be followed to find the correction factor:

•

Compute (N ₁)₆₀ every bit in the previous case.

•

Employ following equations to account for the fines content:

${(N_1)}_{\mathrm{sixty}\text{C}}=a+b{(N_1)}_{60}{(N_1)}_{60\text{C}}=\text{Corrected}{(N_1)}_{60}\text{value}$

(nineteen.13) $a=0\text{for}FC<\mathrm{five}\%(FC=\text{fines}\text{content})$

(19.14) $a=\exp \left(\frac{1.76-190}{F{C}^2}\right)\text{for}5\%<FC<35\%$

(19.fifteen) $a=5.0\text{for}FC>35\%$

(19.sixteen) $b=\mathrm{one.0}\text{for}FC<5\%$

(nineteen.17) $b=\left[0.99+\left(\frac{F{C}^{\mathrm{1.v}}}{1000}\right)\right]\text{for}5\%<FC<35\%$

(19.18) $b=1.2\text{for}FC>35\%$

Blueprint instance three

(N ₁)_threescore value for soil with thirty% fines content was institute to be 20. Find the corrected (N ₁)_60C value for that soil.

$\text{Step}1:{(N_1)}_{60\text{C}}=a+b{({\mathrm{Northward}}_{\mathrm{i}})}_{60}$

(xix.19) $\begin{array}{l}\text{For}FC=30\%;a=\exp \left(\frac{1.76-190}{F{C}^2}\right)=\exp \left(\frac{1.76-190}{{30}^2}\right)=\mathrm{iv.706}\\ \text{For}FC=30\%;b=\left[0.99+\frac{F{C}^{\mathrm{i.5}}}{\mathrm{grand}}\right]=1.154\\ {(N_{\mathrm{ane}})}_{60\text{C}}=\mathrm{iv.706}+1.154\times 20=27.78\end{array}$

Design instance four

Consider a signal at a depth of five m in a sandy soil (fines = 40%). Total density of soil is 1800 kg/g³. The groundwater is at a depth of 2 yard (γ _w = 1000 kg/kⁱⁱⁱ). Corrected (N ₁)_lx value is xv (all the correction parameters C _North, C _E, C _B, and C _R are applied, except for the fines content). Peak horizontal acceleration at the ground surface (a _max) was found to be 0.15chiliad for an convulsion of magnitude 8.5. Check to see whether the soil at a depth of five k would liquefy nether this earthquake load.

Pace 1: find the cyclic stress ratio.

(19.twenty) $\begin{array}{l}\text{Cyclic}\text{stress}\text{ratio}(C\mathrm{Southward}R)=0.65\left(\frac{a_{\max }}{g}\right)\times \left(\frac{\sigma }{{\sigma }^{\prime }}\right)\times r_{\text{d}}\\ \sigma =5\times 1800=9000\text{kg/}{\text{yard}}^2;{\sigma }^{\prime }=2\times 1800+3(1800-1000)=6000\text{kg/}{\text{m}}^2\end{array}$

Since the depth of concern is five grand (which is less than 9.fifteen chiliad) use Equation (19.ii)

$r_{\text{d}}=1.0-0.00765Z\text{for}Z<\mathrm{9.fifteen}\text{1000};r_{\text{d}}=1.0-0.00765\times 5=0.962$

$\text{Hence,}C\mathrm{Due\; south}R=0.65\times (\mathrm{0.xv})\times \left(\frac{9000}{6000}\right)\times 0.962=0.1407$

Pace two: provide the correction factor for fines content.

For soils with xl% fines a = 5 and b = one.2 (Equation (19.15) and (19.eighteen)).

$\begin{array}{l}{({\mathrm{North}}_1)}_{\mathrm{threescore}\text{C}}=a+b{(N_1)}_{60}\\ {(N_1)}_{\mathrm{lx}\text{C}}=5+1.2\times \mathrm{xv}=23\end{array}$

Footstep three: detect the soil resistance to liquefaction.

(nineteen.21) $CR{R}_{7.5}=\frac{1}{[34-(N_1)\mathrm{sixty}]}+\frac{({\mathrm{Northward}}_{\mathrm{one}})60}{135}+\frac{\mathrm{l}}{{[10.{({\mathrm{North}}_{})}_{60}+45]}^2}-\frac{2}{200}$

(Due north ₁)_60C value is constitute to exist 23 (see step ii)

Hence, CRR _7.5 = 0.25 (from Equation (19.4))

(19.22) $\text{Factor}\text{of}\text{rubber}(FO\mathrm{Due\; south})=\left(\frac{CRR\mathrm{7.v}}{CSR}\right)\times M\mathrm{Due\; south}F$

MSF, magnitude scaling cistron.

Obtain MSF from Table 19.1.

MSF = 0.72 for an convulsion of eight.5 magnitude (table by Idris).

CSR = 0.1407 (come across step 1).

Factor of safety (FOS) = (0.25/0.1407) × 0.72 = ane.27.

The soil would not liquefy.

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Site investigation

Ruwan Rajapakse PE, CCM, CCE, AVS , in Geotechnical Engineering Calculations and Rules of Thumb (2d Edition), 2016

two.9 Geotechnical field tests

ii.9.one SPT (N) value

During the construction of borings, SPT (N) values are of soils obtained. The SPT (Northward) value provides data regarding the soil strength. SPT (N) value in sandy soils indicates the friction angle in sandy soils and in clay soils indicates the stiffness of the clay stratum.

2.nine.2 Pocket penetrometer

Pocket penetrometers tin be used to obtain the stiffness of clay samples. The pocket penetrometer is pressed into the soil sample and the reading is recorded. The reading would indicate the cohesion of the clay sample (Figure 2.26).

Figure 2.26. Pocket penetrometer.

2.9.3 Vane shear test

Vane shear tests are conducted to obtain the cohesion (C) value of a dirt layer. An apparatus consisting of vanes is inserted into the dirt layer and rotated. The torques of the vane is measured during the process. Soils with high cohesion values register high torques (Effigy 2.27).

Effigy 2.27. Vane shear apparatus.

2.9.3.1 Vane shear test process

•

A drill hole is made with a regular drill rig.

•

The vane shear apparatus is inserted into the clay.

•

The vane is rotated and the torque is measured.

•

The torque would gradually increment and attain a maximum. The maximum torque achieved is recorded.

•

At failure, the torque would reduce and reach a constant value. This value refers to the remolded shear strength (Figure ii.28).

Figure 2.28. Torque versus time curve.

The cohesion of clay is given by

$T=C\pi (d^{2}h/\mathrm{two}+d^{\mathrm{three}}/\mathrm{vi})$

T, torque (measured); C, cohesion of the dirt layer; d, width of vanes; h, meridian of vanes.

The cohesion of the dirt layer is obtained by using the maximum torque. Remolded cohesion is obtained by using the torque at failure.

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Soil Mechanics Nuts, Field Investigations, and Preliminary Basis Modification Blueprint

Peter G. Nicholson , in Soil Comeback and Ground Modification Methods, 2015

Relevant ASTM Standards

D1586-11 Standard Test Method for Standard Penetration Examination (SPT) and Divide-Butt Sampling of Soils, V4.08

D2166/D2166M-thirteen Standard Test Method for Unconfined Compressive Forcefulness of Cohesive Soil, V4.08

D2435/D2435M-11, Standard Exam Methods for Ane-Dimensional Consolidation Properties of Soils Using Incremental Loading, V4.08

D2487-eleven Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification Organisation), V4.08

D3080/D3080M-11 Standard Test Method for Directly Shear Test of Soils Under Consolidated Conditions, V4.08

D3282-09 Standard Practice for Nomenclature of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes, V4.08

D4186/D4186M-eleven Standard Exam Methods for One-Dimensional Consolidation Backdrop of Saturated Cohesive Soils Using Controlled-Strain Loading, V4.08

D4318-x Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, V4.08

D4546-08 Standard Examination Methods for One-Dimensional Swell or Collapse of Cohesive Soils, V4.08

D4633-10 Standard Examination Method for Energy Measurement for Dynamic Penetrometers, V4.08

D4719-07 Standard Test Methods for Prebored Pressuremeter Testing in Soils, V4.08

D5778-12 Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of Soils, V4.08

D6391-xi Standard Test Method for Field Measurement of Hydraulic Conductivity Using Borehole Infiltration, V4.09

D6528-07 Standard Examination Method for Consolidated Undrained Direct Simple Shear Testing of Cohesive Soils, V4.08

D6635-01 Standard Test Method for Performing the Apartment Plate Dilatometer, V4.08

D7181-11 Standard Test Method for Consolidated Drained Triaxial Compression Test for Soils, V4.08

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Geotechnical engineering theoretical concepts

Ruwan Rajapakse PE, CCM, CCE, AVS , in Geotechnical Engineering Calculations and Rules of Thumb (2nd Edition), 2016

5.7.7 Bear on due to earthquakes

Imagine a bullet hitting a wall (Figure 5.31).

Figure 5.31. Bullet hitting a wall.

The extent of the damage to the wall due to the bullet depends on a number of parameters.

Bullet backdrop

ane.

Velocity of the bullet.

2.

Weight of the bullet.

iii.

Hardness of the bullet material.

Wall properties

1.

Hardness of the wall material.

2.

Blazon of wall material.

The parameters that affect liquefaction are as follows:

Earthquake properties

•

Magnitude of the earthquake

•

Peak horizontal dispatch at the footing surface (a _max)

Soil Properties

•

Soil strength (measured past Standard Penetration Exam (SPT) value)

•

Effective stress at the signal of liquefaction

•

Content of fines (fines are defined as particles that pass through the #200 sieve)

•

Convulsion properties that affect the liquefaction of a soil are confederate into 1 parameter known as circadian stress ratio (CSR).

(ane) $\text{CSR}=0.65(a_{\text{max}}\text{/}g)\times (\sigma /\sigma \text{'})\times r_{\text{d}}$

•

a _max = elevation horizontal acceleration at the ground surface; σ = total stress at the point of business organization; σ′ = effective stress at the bespeak of business; r _d = stress reduction coefficient (this parameter accounts for the flexibility of the soil profile).

(1.one) $r_{\text{d}}=\mathrm{i.0}-0.00765Z\text{for}Z<\mathrm{nine.15}\text{thou}$

(1.2) $r_{\text{d}}=\mathrm{one.174}-0.0267Z\text{for}\mathrm{9.fifteen}\text{k}<Z<23\text{thou}$

Z = depth to the bespeak of business concern in meters.

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Site investigation, characterization and assessment for current of air turbine design and construction

J.Chiliad. Tinjum , R.W. Christensen , in Current of air Energy Systems, 2011

Parameters for the solution of allowable bearing pressure equation

Sampling to accost bearing capacity and settlement usually involves SPTs and thin-walled tube sampling, similar to what would be done for whatever large foundation. Laboratory strength testing will depend on the soil types encountered in the contour, such as unconfined compression or unconsolidated–undrained test for cohesive soils. Rarely, triaxial and/or direct shear tests may also be conducted. Additionally, CPT probes are frequently used to assess undrained shear strength of clays. Typically, in the example of granular soils, strength or begetting capacity is based on correlations with the SPT blow counts and/or CPT cone resistance. To perform a standard commanded bearing pressure analysis, the post-obit soil parameters are required:

•

internal angle of friction (ϕ′, drained strength),

•

undrained strength (c or S_u),

•

unit weight of soil, γ

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Substation and Overhead Line Foundations

Dr C.R. Bayliss CEng FIET , B.J. Hardy CEng FIET , in Transmission and Distribution Electric Engineering (4th Edition), 2012

15.2 Soil Investigations

Footing investigations are carried out by geotechnical experts using boreholes, trial pits and penetrometer tests.

Investigations take the form of in situ and laboratory tests. In situ tests include standard penetration tests to provide data on the relative density to sand for the more coarse-grained soils.

Laboratory investigations on soil samples taken from boreholes or trial pits will measure out grain size, density, shear strength, compressibility, chemical limerick and wet content such that the soil can exist categorized.

Figures fifteen.1a and 15.1b give a useful guide for estimating soil types based on cone penetrometer terminate resistance and friction ratio. Examples of Heart East and UK substation soil penetrometer site investigations are given in Figs. 15.2a and 15.2c. Soil chemic test results, grain-size distribution, consolidation and plasticity are given in Figs. xv.3a to 15.3d, respectively.

Figure 15.1a. Guide for estimating soil blazon from penetrometer testing.

Figure 15.1b. Guide for estimating soil type from penetrometer testing.

Effigy xv.2a. Soil investigation borehole contour

(courtesy of Foundation and Exploration Services).

Effigy 15.2b. Dutch cone penetrometer and accessories.

Effigy 15.2c. Dutch cone penetration test.

Figure fifteen.3a. Soil chemical test results

(courtesy of Foundation and Exploration Services).

Figure fifteen.3b. Soil grain size distribution.

Figure 15.3c. Soil consolidation test results.

Effigy xv.3d. Soil plasticity test results.

Guidance on geotechnical design is provided in Eurocode vii (EN 1997).

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Deep Densification

Peter One thousand. Nicholson , in Soil Comeback and Ground Modification Methods, 2015

6.ii.i.4 SPT and CPT

Density of in situ deposits, equally well equally liquefaction potential, are commonly evaluated with SPT and/or CPT penetration tests. Every bit such, they are often used for before and afterward testing to evaluate densification improvements (Effigy 6.20). These common field tests (described in Section 3.3.2, Field Tests) are standard tools for field investigations and provide a wealth of information that allows reasonably skilful correlations to densities, strength parameters, liquefaction potential, and so forth. In this lite, penetration tests (particularly CPT for cost and efficiency) are besides sometimes used during construction to evaluate the densification progress. These tests tin can also ensure quality in construction specifications every bit discussed in the following section.

Figure 6.20. Example of improvement in penetration resistance before and later on DDC.

Courtesy of Densification, Inc.

Piezocone (CPTU; ASTM D5778) testing enables pore pressure measurements to exist made in conjunction with penetration resistance measurements. While these are but unmarried temporal measurements of pore pressures, they may exist useful for interim analyses.

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