Spt n value table. I don't have a value for N=0 because, well, it is sometimes hard to sample especially with crude equipment. Bowles method – The equation proposed by Meyerhof and Tong were found to be very conservative and Bowles (1982) modified these equations. C N. Research has shown that the most significant factor affecting the measured N values is the amount of energy delivered to the drill rods. Its definition is derived from the Mohr-Coulomb failure criterion and is used to describe the friction shear resistance of soils together with the normal effective stress. Table 1 Approximate ranges of ( ’)and corresponding SPT - N for cohesionless soils (Meyerhoff 1956) Soil packing SPT - N values Internal angle of friction ( ’) ( ) Very loose < 4 < 30 Loose 4 - 10 30 - 35 Compact 10 - 30 35 - 40 May 7, 2013 · Each boring log has N values at different depths using the SPT test. α = 1 for displacement piles in all soils and non-displacement piles in clay. Aug 9, 2020 · where, N s. N s = SPT value along pile shaft. The mean standard deviation for each Expert-verified. Feb 3, 2022 · For the alluvial clayey silt or silty clay (Ac 1) layer, the R 2 value is 0. Where; N': SPT value after silty sand correction (dilatancy correction) (Terzaghi & Peck, 1948) If the below 3 conditions are present, silty sand correction should be made. The SPT, while used less frequently, is still used today. SPT Penetration, N-Value In addition, SPT-N corrected values have also been obtained for all soil types within the Surfers Paradise soil profile (Table 3) Friction angle and apparent preconsolidation stress Hatanaka N C = 15 + 0. In addition, the settlement calculation and liquefaction analysis of cohesionless soils are based on the SPT N values. Relation between phi and SPT value (N) Step-5 8 shows thecomparisons between SPT N-value and the normalized N-value calculated from thepenetration resistance of CPTand SWS using conversion formulae shown in Table 2 for the rele vant cases The maximum values of base pressure under the foundation for both the average and the minimum bearing capacity values for Mosul region for the normal strength concrete and air-en-trained were (94 Download Table | SPT-N value parameters based on reduced level depth from publication: Subsurface Visualization of Peat and Soil by using GIS in Surfers Paradise, Southeast Queensland, Australia May 26, 2007 · The aformentioned graphs are presented in "Engineering Properties of Soils", UCLA-ENG-7652, May 1976 by Ladd and Lee. 6 MPa for fine grained Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the friction shear resistance of soils together with the normal effective stress. 1 (informative) Standard Penetration Test (SPT) Table D. 25%. The energy ratio for the SPT test was 72% a) Determine the Noo and (N1). This is useful in coarse granular soils where representative or undisturbed samples cannot always be recovered for laboratory testing. The equations that are commonly used were proposed by Meyerhof based on one inch of foundation settlement. By inspection, this query returns a list of 2048 consecutive integers: select number from master. Note that most of these correlations use the “uncorrected” SPT N-values and therefore are subject to some variability, depending on the system used in developing the correlation. spt_values; it contains numbers from 0 to 2047. Table 2 Ranges of SPT N value with Cohesion for intermediate soils SPT N value [30 10–30 \10 Cohesion, kPa 48 5–48 5 Soil conditions Dense Medium Loose Data from Karol (1960) S = 0. However, this required the correlation of the DCP against the SPT N-values in order to be able to properly interpret The standard penetration test, commonly known as ‘SPT’, was developed to provide geotechnical engineering properties for foundation design purposes. Step-4. The coefficient of correlation (R) values for the developed bearing capacity prediction model ranged from 0. Jul 11, 2021 · Table 1 represents the summary of correlative works which have been done in the past to develop correlations between SPT N-values and CPT cone bearing resistances, q c. 0 30. The test involves driving a standard thick-walled sample tube into the ground at the bottom of a borehole by blows from a slide hammer Jun 1, 2015 · The corrected blow count is then designated as N 60 and the normalized value (N 1 ) 60 at unit effective pressure (1 kg/cm ² or 100 kPa) may be regarded as a basic characteristic of the sand. 33D f /B ≤1. 1 This test is the most frequently used subsurface exploration drilling test performed worldwide. 60. The N-value provides an indication of the relative density of the subsurface soil, and it is used in empirical geotechnical correlation to estimate the Nov 25, 2010 · 1. 89 N 78 0. spt_values is being used in its place. All the 20 models have been ranked based on their overall performance including their prediction capability, R 2 value of the correlation and the SPT-N values were analyzed in this study. 98–0. This is my current method: The average value of Friction ratio is 1. The N-Value is the sum of the last 2 blow counts, which in your example (25-30-50/0mm) would be N=80 if you stopped after 50. 65, and G m a x can be estimated at the given E R m. Annex D. (SELECT 1 FROM Numbers. 2. Dec 5, 2022 · Table 2 provides information about the CPT and SPT test results for the phase 14 site in South Pars. The results can be used to determine the relative density, bearing capacity, and settlement of granular soil. Mar 5, 2021 · Table 2-2: Empirical values for ρ t, of granular soils based on the standard penetration number, (from Bowels, Foundation Analysis). α = 0. Soil Types. Of course, the application of the empirical methods to prepare the direct information about the studied site, but several limitations have to be considered during site investigations. The a m values for different E R m are presented in Table 1. R d = Depth correction factor = 1 + 0. For information on alleviating compacted soils, link here. The consistency of clayey soils can often be estimated from Feb 5, 2014 · Mike Lambert. 1: Estimated values of soil cohesion and friction based on uncorrected Standard Penetration Test (David, 2006). N b = SPT value close to pile tip. May 3, 2022 · ASTM D1586/D1586M-18e1. C S. . 2657, which indicates that there is a poor correlation between equivalent SPT N 60-value and corrected SPT N 60-value. The N values have been taken from 3 different soil layers. Type A: Rock or Hard soil. It is simply because SPT numbers are readily available from soil boring. nbr1 (Geotechnical) 5 Feb 14 21:11. Oct 18, 2016 · The empirical relationships have also been developed in terms of field Standard Penetration Test (SPT), N value. The soil samples are classified as poorly graded sand (SP), poorly graded sand with silt (SP-SM) and silty sand (SM) on the basis of Unified Soil nology was applied to SPT measurements in a similar way to observe the set and energy. 99998917 SPT N value a P k, C, n o i s e h o C 0 What are the meanings of its type, low, high values? Update: Google search gives thousands of " its uses", for example: to split column using master. Nov 1, 2021 · Higher bound: G m a x = 28. Sep 14, 2022 · Here, the N SPT value does not directly provide the c u value that is used as a geotechnical design parameter. 99988490 SPT N value a P k, C, n o i s e h o C 0 0. 4 Graph of SPT-N value obtained from seismic survey test at Perlis 47 Figure 4. The reported values of effective friction angle (ϕ′), based on SPT N60 values, should be reduced by 5° for clayey sands and should be increased by 5° for gravelly sands. ) increments is called the SPT N value (with units of blows per 0. Figure 2 is Jan 1, 2017 · The relationship between SPT N-values and cone tip resistance q c is defined by a ratio “n” where n = q c /N. Introduction. For Ganga Basin, Maheshwari et al. The boring logs reach a depth of 20 m and I'm interested in the N value of a sand layer that is only 10 meters deep. The soils found in eastern Saudi Arabia, especially in coastal areas are generally cemented and calcareous in nature with shallow water tables. (1. When the SPT N-value is zero, previous models [4, 34 Aug 17, 2023 · The SPT (N) value provides information regarding the soil strength. 5 (±0. Dense silty sand, silty sand along with fine gravel particles, and weathered Charnockite rock are reported as refusal layers at the test locations. Correlate the above cumulative average SPT value with the fig given below to find out the corresponding angle of shearing resistance (ϕ). 81 m/sec2 or 32. 98 for C soil, C-φ soil, φ soil respectively. In essence, the Meyerhofs expression specifies that the ratio between the normalized SPT N value and the square of the relative density, Nj / Dr, is fixed at 41. 24 ~ 18. This can be used to determine the apparent . However, the coarser soil layer As 1 and As 2 the coefficient of correlation (R 2 ) are 0. 3556 SPT + 20. C BF. If there are two granular soils with 2. 5 − 0. If N 1 < 15 then this correction is not required. Mar 8, 2023 · Increase in Net Safe Bearing Capacity (SBC) on soil in design of foundation. It is very useful. of penetration is reported as SPT blowcount value, commonly termed "standard penetration resistance" or the "N-value". , PMP 6 Comments. spt_values where type = 'P'. 2 ft/sec2). Shear wave velocity was determined by using universal correlation of Shear wave velocity and Standard penetration Test Apr 25, 2017 · The SPT-N values were observed to vary between 4 and 100 and the in-situ bulk density of undisturbed samples as recovered through pitcher sampler are in the range of 13. N' C E. 77536983 r = 0. 9. In the stress plane of Shear stress-effective normal stress, the soil friction angle is the angle of inclination with respect to the horizontal axis of the Mohr-Coulomb Measured SPT values in the field (N) at each depth (z) will be corrected to (N 1) 60 values using the equation below. have carried out MASW and SPT for two locations namely Dhanauri and Roshnabad and developed correlations between V s and N value. 75 and the low SPT-N value of the clay layer, the frictional Feb 16, 2023 · The values shown in this table are for uncompacted soils. density are shown in Table 3-1. The water table is at a depth of 2 m. The Standard Penetration Test is an in-situ test that is useful in site exploration and foundation design. In the dilatancy correction formula, we have to take the value of N1 > 15 always. 1 Correction Factors Since the introduction of the SPT in 1902, the drop hammer systems have evolved from pin weight to Sep 17, 2013 · N = SPT value corrected for overburden pressure. If N R less than or equal to 15, then N c = N R 2. The spreadsheet also includes unique analysis tools which Jul 13, 2023 · The dilatancy Correction formula in SPT is N2=15 + 1/2 ( N1-15 ). Table 2 shows the correlation between N SPT and c u according to soil classification from the literature [7,8,9]. Jun 2, 2018 · The number or blows required for 12 inches penetration resistance of the soil. Many common solutions for splitting strings in TSQL require a list of numbers; in this case, someone is using the spt_values table to provide them. Since the cut-off level of the shaft at GL -23. The SPT N values of the boreholes have been shown in the Table 1. Table 1. Silty fine sands and fine sands below the water table are subjected to the pore water pressure. In the case of Ks-Delta method, each skin segment will then have its own computed friction angle. 6 Correlation of Bearing Capacity, Q from Seismic Survey and (c’ and ϕ) 51 Figure 4. But for N=1, the undrained shear strengths I correlated are about 15 to 20kPa. b) Determine the Noo value that you would expect to Mar 8, 2011 · That is the syntax for specifying a databasename, schema, and table name. The sum of the number of blows required for the second and third 6 in. The measured SPT N values and bulk density at 23 locations were considered to develop correlations between the SPT N and in situ bulk density. Note that this provides a picture different from the previous SPT values used for strength based on defects only The CivilWeb Soil Bearing Calculation from SPT Value XLS Spreadsheet allows the user to estimate the bearing capacity of a soil from its SPT n value. values for this SPT test. Overburden Pressure Correction From several investigations, it is proven that the penetration resistance or the value of N is dependent on the overburden pressure. Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils. In order to reduce the significant variability of the SPT N-values due to the large variation in energy delivered, it has been recommended that the N value be One of most common methods for determining allowable soil bearing capacity is from standard penetration test (SPT) numbers. 05738568 r = 0. Equivalent SPT N 60 Before the CPT came into popularity, the Standard Penetration Test was the standard soil test. Nov 1, 2021 · This modified coefficient. 12. In the stress plane of Shear stress-effective normal stress, the soil friction angle is the angle of Sep 1, 2016 · Table 2. 83 N 60 0. normalStres Feb 6, 2018 · A portable standard dynamic cone penetrometer (DCP) was used to overcome the challenge encountered in generating SPT N-values for the design of the foundation of power transmission towers traversing a tropical forest, large parts of which was inaccessible to motorized transport. 50%. The averaged shear wave velocities are then plotted against the SPT-N values and thus the correlations are developed. These energy values on the hammer and below the anvil was . C R. Figure 2 shows Depth (m) vs. 44 kN/m3. When earthquake forces are included, Net safe bearing pressure of soil can be increased as per given table below depending on type of foundation and type of soil. Pocket penetrometer Correlations of SPT blow counts to cohesionless soil friction angle and unit weight follow Bowles (1977) and are consistent with many of the NHI manuals used by the department. 1: Values of the energy ratios ERr of the common equipment used in various countries and the correction factors to apply for normalizing to ERr = 60 % Country Hammer Release ERr (%) ERr/60 North and South America DonutSafetyAutomatic 2 turns of rope 2 turns of ropeTrip 45 5555 to 83 0,75 0,920,92 to 1,38 Japan Engineering. N 60 (N 1) 60 {{tabaka. Therefore, each skin segment has an assigned SPT N value. Table 2: Relationship among relative density, SPT N value, and internal friction angle of Shear wave velocity (VS) is a valuable indicator of the dynamic properties of soil and rock because of its relationship with Gmax, given by Equation (1. The Standard Penetration Test (SPT) is a widely used in-situ testing method to determine the geotechnical engineering properties of subsurface soils. Jun 1, 2009 · According to R2 , RMSE & MSE value the best correlation is chosen among several combinations of N, N60, N1,60, depth & grain size data for Angle of Internal Friction (φ) and N, N60, depth Very early in the history of the SPT, data were collected that showed that rotary drilling with clear water resulted in N values that were much lower than those in which drilling mud was used. Different G m a x values estimated Nov 25, 2023 · SPT N Value Bearing Capacity Correlations. 15m (6in. Particular care should be taken in applying these classification terms in coarse gravels; they should not be used for very coarse soils. Question 2: An SPT N value of 22 is measured at a depth of 16 m in a deep deposit of clean well graded and poorly graded sands (SP and SW). Here N2 is the final corrected value after water table correction and N1 is the corrected value after overburden correction. R w = Water table corrected factor. , for estimation of shear wave velocity, bearing capacity etc The Standard Penetration Test (SPT) October 31, 2013 by Bernie Roseke, P. For Guwahati city in India, contour maps using standard penetration test SPT-N values, ground water table and shear wave velocity were established based on borehole data of 200 sites (Sharma and Relatively low SPT-N values were observed from ground surface down to about 30m deep. = 15 + 0. The results can also be used to Jun 8, 2023 · Before the SPT values can be used in empirical correlations and design charts, the standard penetration value N needs to be corrected as per IS 2131. Empirical relationships to approximate the soil friction angle (φ) and . This indicates that the PSO-ANN models predicted the output near to the actual value. The N value is a value obtained by a standard penetration test (SPT) [17] [18] [19]. The correlations use Standard Penetration Test (N) values corrected for overburden and hammer efficiency (N160). and clayey gravels with sand ( ’) = 0. 35 MPa for clay and silty clay, 0. 646. 5 Graph of SPT-N value obtained from seismic survey test at Pekan 48 Figure 4. It is generally referred as the ‘N’ value and measured in blows/unit penetration. SPT (N) value in sandy soils indicates the friction angle in sandy soils and in clay soils indicates the stiffness of the clay stratum. The SPT N-values in the study range from 7 to 100 (assuming N = 100 for refusal). 6 for non-displacement piles in granular soils Those correlations were presented in Table 5, and they were also plotted in Figure 3 for visual comparison. 5(N measured-15) The SPT is more reliable for granular soils as compared with fine grained soils. In estimation of other parameters also, SPT N value is used e. For skin segments, the SPT N value is taken at the depth of the segment. 534 respectively, which indicate reliable Calculate the corrected SPT values N60 and N160 for a given borehole log. g. N in present procedures. 65. blows with no advance on the last spoonwhich most would. Mar 12, 2020 · You can estimate the elastic modulus by using different correlations as a function of corrected SPT N-values and undrained shear strength, as follows: (a) E = 18 N 60 for coarse-grained materials Aug 2, 2017 · An averaging technique for developing correlations has been adopted combining all the selected equations in estimating shear wave velocities using SPT-N values ranging from 3 ≤ N ≤ 50. 0 20. 0 0 0 0 0 S = 0. You can use this syntax to specify a database different from the database you are currently connected to. 3 Correlations Between DCP and SPT make direct use of the SPT N-value and the test itself has been made an integral part of routine site There is not much data in the literature on the direct investigation, there are many situations where either correlation between SPT N-value and DCP blow the Mar 21, 2019 · Hence, the determinations of in situ void ratios and/or relative densities of uncemented sands are generally achieved using correlations with the cone penetration test (CPT) and the standard penetration test (SPT). 1. 0 10. So, SPT-N value obtained is lower than actual value. - "Predicting Standard Penetration Test (SPT-N) Value from Electrical Resistivity Result" Correction for overburden No pressure, (N1)60 (1) Fine sand/silt (2) Below water table (3) (N1)60 > 15 Yes No Correction for water table, (N1)60(CORR) END Correction 1: Correction of SPT Value for Field Procedures N60 N H B S R N 60 60 N60 = standard penetration number, corrected for field procedure N = measured penetration number H = Hammer more than standard SPT spoon and we get the lower value of SPT. Type B: Medium or Stiff soil. SPT N values shall be corrected for hammer efficiency, if applicable to the design method or correlation being used, using the following relationship. During the construction of borings, SPT (N) values are of soils obtained. The 3 data points for the N - value are measured as 30,000 data points. DM-7 presents relationships for SPT n-value and unconfined compressive strength for clay. As the SPT-N value is expressed in two ways in South Korea (the number of blows/30 cm or 50 blows/penetration depth), every SPT-N value was Apr 29, 2018 · Table 1 illustrates the effects of different drilling and mechanical variables on the SPT “N” value (items 1 through 5). Engineering judgment should be used in selecting a specific value. Apparent Density If SPT is performed below GWT, the SPT-N values is overestimated and a correction to measured N is (dilatancy correction) applied if SPT-N value exceeds 15 N corr. November 25, 2023. Use Chart 1 to correlate N160 to the friction (phi) angle. It produces an N-value, which represents the number of blows of a standardized sampler driven into the soil a standardized distance. Link to this table SPT N values of nine boreholes were collected from Standard Penetration Test. Properties Granular Soils . In case of gravels, a 60o cone is used in stead of split spoon samples Dec 11, 2015 · N r = average SPT (N 60) value within depth of one-half of the footing width. The Standard penetration test ( SPT ) is widely used to get the bearing capacity of soil directly at a certain depth. In this table a typical N value in clean quartz sand is 20 blows per foot. ) penetration is considered by ASTM as a “seating” penetration and the sum of the hammer blows for the second two 0. 2. 97–0. If a soil is compacted, reduce the soil infiltration rate by one level (e. This situation has led many researchers to develop other correlations to predict the c u value using N SPT [4,5,6]. Table 3-1. The SPT (N) value provides information regarding the soil strength. N. Correlations based on SPT N values are extensively used for the estimation of design soil parameters. I've collected all the N values and depths for each boring. Significance and Use. 4. SPT N. The total number of SPT-N values that were analyzed for weathered residual soil was 742, and that for weathered rock was 432. 1) where soil density (ρ) is the total unit weight of the soil divided by gravity (9. Nov 19, 2003 · For very soft clays here in West Bengal, I developed a curve of SPT N values to undrained shear strengths (field vanes - corrected - and qu tests). Different sands of the same relative density may have dissimilar CPT and SPT resistances because of their compressibility Figure 4. 7106 and 0. It has been recognized, however, that the penetration resistance Feb 28, 2023 · The initial 0. Mar 3, 2017 · density using SPT N-value are presented in Table 1. Cone Resistance qt (MPa) Table 1. As Mike indicated, you could report as 80/150mm assuming no advance on last spoon. When corrected for the SPT hammer’s energy efficiency, it becomes N. Example of SPT N-values 5. Theenergy corrections are required with the in situ N – values to be effectively used as a design value. 69 Source: Paul Mayne (based on data from VTrans) Figure 5-3. De Alencar Velloso (1959) presented ratios of cone tip resistance to SPT N -value for different soil types, 0. 11. The equations proposed are: Teng’s modified equation, Mar 30, 2015 · Calculate the cumulative average value of corrected SPT values from the base level of foundation to a depth equal to 2 times the width of foundation. K 1, K 2 = factors shown in Table 4. Percentage Increase Allowable. Apr 20, 2016 · The SPT N value provides an indication of the relative density of the subsurface soil and is used in empirical geotechnical correlations to estimate its approximate shear strength properties. 35 MPa for sandy silt, 0. There have been many attempts by researchers to relate the SPT N value to the CPT cone penetration resistance q c. What Is SPT Boring? The number of blows required to drive the sampler through the 6- to 18-inch interval is termed the SPT N-value and is Sep 27, 2021 · Standard penetration test (SPT) is one of the in-situ tests conducted for onshore and near shore soil investigation projects. for a compacted B(SM) use the infiltration rate for a B(MH) soil). Mar 7, 2008 · There are many charts, tables and empirical relationships are available in the literature between the SPT N value and the angle of internal friction ( and undrained cohesion (c u ) by different Mar 11, 2016 · For Delhi city, Hanumantharao and Ramana had measured shear wave velocity using SASW for 80 locations to a depth of 20–32 m and developed correlations between V s and N value. So, create such a tally table, and the query (if the logic is correct) now becomes: CROSS APPLY. ‘ a m ’ can be multiplied with ( N E R m) 0. As an example, for E R m = 60 %, the following equation shall be used to estimate G m a x G m a x = 13. 99, 0. 1 SPT (N) value. 5) kg weight is dropped from a height of 76 (±1) cm, and the rod of the special An alternative is to use the SPT N-value to estimate the unconfined compressive strength (UCS) as noted in Table 2. In this case, a subset of rows from the undocumented table master. Soil friction angle is a shear strength parameter of soils. The test is carried out within a borehole. SPT N value Fill CDG MDG 0 25 50 75 100 SPT N value Fill CDG MDG 0 1020304050 SPT N value Fill MD AL 01020304050 SPT N value Fill 0 20 40 60 80100 SPT N value MDG N value Fill CDV MDV/SDV Measured SPT N value Linear regression N 95L profile (a) (b) (c) (d) (e) (f) (g) 0 5 10 15 20 25 Depth (m) SPT N value Figure 3. 703 based on SPT - N values. This table can be used as a guide to determine if a soil is compacted. for example if you need to populate a table with 100 numbers from this range; for building indexes; creating virtual calendars sampler, is referred to as N value. The corrections are: Correction for Dilatancy; Overburden Pressure Correction; Dilatancy Correction. Two factors were involved, 1) the water from drilling was jetted into the test interval disturbing Interpretation of SPT N Values from Table AVERAGING SPT N VALUES. 2 MPa for sandy clay and silty clay, 0. 1): Gmax = ρ · VS 2. com Oct 5, 2018 · Each row of that table contains a distinct integer value. C B. i is a verage number of SPT in i th soil la yer; N p is average value of SPT blow counts taken within a zone 1D below pile tip level a nd 4D above level o f pile tip . Table 2 can then be refined for the various rock types as shown in Table 3. Even though many foundation design procedures 1. 5 (N R -15) Where N R is the recorded value and N C is the corrected value. This graph compiles the various correlations by Sowers, and Terzaghi & Peck. 3m or blows per ft) and is the reference measurement obtained from the test. Unlike the old correlation models only required soil type and N-value to predict Su The numerical SPT N-values on the log should be uncorrected (see CIRIA R143 ) and the relative density classification term should be applied in accordance with Table 10. (N 1) 60 = N' x C E x C N x C B x C S x C R x C BF. 31 N 78 0. density of a granular soil. Bowles revised Meyerhof’s equations soil properties are based on N60-values. SPT N value is widely used as it is an index for quick strength characterization due to its simplicity. In Figure 1, angle of driving shoe of standard SPT spoon is 16º to 24º and the cutting edge is not sharp which gives the actual value of SPT. In the SPT, a 63. Eng. USCS. The total An example profile of measured SPT N-values from a boring by the Vermont Agency of Transportation (VTrans) is presented in Figure 5-3. 7 Correlation of SPT-N value from seismic survey and SPT-N boreholes 52 Sep 4, 2021 · This was proved by the R and MSE values used for evaluating the model. 60 = (ER/60%) N (5-1) Where: N = uncorrected SPT value (blows/ft) N60 = SPT blow count corrected for hammer efficiency (blows/ft) Jun 1, 2020 · The new trend acknowledges a critical limitation in the models of previous studies, which fail to account for the case of an SPT value of "0". In your example, master is the database name, the schema name is unspecified (so it becomes the default dbo schema) and spt_values is the table name. 33. 648 Lower bound: G m a x = 9. Note that this provides a picture different from the previous SPT values used for strength based on defects only Karol (1960) [15] has proposed a correlation between the soil cohesion and SPT-N values based on the soil conditions that vary from very soft to hard conditions corresponding to SPT-N and cohesion Jan 30, 2001 · correlation between the SPT N value and relative density Dr for clean sands. jj nm zh ho ah bd vw ha gu vv