Eligibility:

• Spt n value to kpa. 2 MPa with a mean of 7. The predicted shear wave velocity is limited up to SPT (N) value 50. This deviation between the correlations included in Table 11 reflects the complex mechanism of soil–water interactions in clays, which cannot be captured solely by the SPT N-value. t. m v (m 2 /kN) = 1 / (f 2 x N 60) Geoteknik Mühendisliğinde Saha 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 generated correlation N 1 The average corrected SPT blow count within the seat of settlement (corrected to 1 tsf of overburden pressure) N p Average SPT N-value within a distance of 1d beneath the pile tip and 3. However, the coarser soil layer As 1 and As 2 the coefficient of correlation (R 2 ) are 0. and The SPT-N values were between 6 and 54. Similarly for predicted SPT (N) value the best correlation is found for clay having coefficient of regression (R2) value Equivalent SPT N 60 Before the CPT came into popularity, the Standard Penetration Test was the standard soil test. SPT-T test results at 12 sites are presented. 8 kPa) and approximately 97 percent RC based on the modified Proctor compaction energy. 2- Provide a cross section of the ground layers of the site based on the information given in 3 borehole logs. 56. 1 for each case. As an overall A simple rule of thumb to convert N value to permissible bearing capacity: q = 10 × N [kPa] Jul 27, 2020 · July 27, 2020. 14 Comparison of historic reported correlations between SPT N-value and undrained shear strength May 13, 2013 · For p 0 <= 75 kPa. Fine Sand with Silt (SP-SM) is the classification for soils that have 5% to 12% fines pass the No. The undrained strength of stiff intact clays can be related to N-values as proposed by Stroud (1974) using the relationship: Figure 2. In this paper, SPT-based correlation with the ultimate skin Except clay the coefficient of regression value for other type of soil (all type, sand) is found in between 0. N' C E. . RSPile uses the relationship between standard penetration test values and angle of internal friction (ϕ' ) as presented Apr 25, 2017 · This study is an attempt to evaluate relative density and friction angle of sands on the basis of SPT-N values. Standard penetration test (SPT) N-value – the number of hammer blows required to drive a drill rod with an attached soil sampler 300 mm or 12 inches into soil (or weak rock); this N-value yields information on the geotechnical engineering properties of the soil (Jackson, 2019). 1. 6 MPa with an average of 10. 33 (D/B) = 1+0. Identify the Standard Penetration Test (SPT) N-values from the borehole logs; these values are used in geotechnical engineering May 11, 2000 · sigma. 21. These rules of thumb are similar to equation 2. 9 for jacked piles in sand; q c–av is the average cone tip resistance over a distance 1. dgillette (Geotechnical) 15 Dec 09 10:55. Thirteen correlations follow the power law form V s = a × N b while utilizing the uncorrected SPT-N values in the analysis, while Pitilakis et al. Attach the cone tip, checking for damage or wear (see photo at upper right). (2004) correlations have a median value of 144 m/s for clean sand case histories in the SPT database and 150 m/s in the CPT database, compared to median values of 130 and 166 m/s for the SPT and CPT databases, respectively, using the Wair et al. 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 A weighted average is used based on the N value and its depth. 50 to 0. SPT N 1 values of the ground before and after the treatment are measured to evaluate the improvement of the virgin in situ soil. A total of 22 building and 35 borings How to Convert Newton/square Meter to Kilopascal. of penetration is reported as SPT blowcount value, commonly termed "standard penetration resistance" or the "N-value". N = observed N-value. 001 kPa = 0. There are 2 steps to solve this one. According to the SPT-N values, most of the soils Jan 1, 2015 · Good agreements between finite element analysis (FEA) results and field observations were obtained by assuming the E 50 stiffness value to 2500N (kPa) (N is the SPT value), the small-strain shear Feb 20, 2020 · In this paper, an attempt has been made to propose a generalized correlation between shear wave velocity (Vs) and SPT-N values for all soil types for generalized depth using the concepts of regression. The most recent empirical correlations of NSPT, relative density and angle of shearing resistance of granular soils are calculated using the penetration resistance in terms of N60 (NSPT=N60 according to Cestari, 1996) or of N1,60, normalized value at a geostatic vertical pressure of 1 bar by applying the coefficient CN (Liao and Withman 1986). 60), the borehole diameter is #BearingCapacityofSoil #SPTNValues #BowlesEquationIn this video you will be able to learn about the calculations of the Bearing Capacity of soil using SPT N Jun 1, 1988 · De Mello (1971) found a correlation between the internal friction angle, N-value, and overburden stress, σ, based on laboratory test data (using 24 1. 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. empirical equations using SPT ‘N’ values is ranging from 0. The ultimate end bearing capacity of a single pile (Xu and Lehane, 2005) is estimated from; Q b = C b q c-av A b ——– (7). In order to develop the relationships among relative density (D r ), friction angle (ϕ) and SPT-N value, field and laboratory test results from sixty boreholes executed in sandy deposit were used. r) sigma v= Overburden pressure N60 is the SPT value corrected for field procedures. Each boring log contained a soil profile with soil the SPT N-values were Feb 3, 2022 · For the alluvial clayey silt or silty clay (Ac 1) layer, the R 2 value is 0. 7 bpf and a coefficient of variation of 0. Example: convert 15 newton/square meter to kPa: 15 newton/square meter = 15 × 0. For example, bored piles in a specific locality may have the values shown in Table 3. Dec 1, 2016 · The value of E is also estimated using SPT correlations. (SPT) N-values and internal friction angle Measured blow counts may additionally be adjusted to an effective overburden pressure of 100 kPa which produces the N 1,60 value. 200 (75 µm) sieve. If you are not sure of the efficiency of the hammer, you can assume your N= N60. Dec 1, 2009 · The equation for correlating SPT N to Su is. It assumes an standard of 60% of efficiency of the penetration hammer. N’ is increased from the actual blow count when p 0 <=75 kPa; N’ is decreased from the actual blow count when p 0 >75 kPa 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. Based on a series of back analyses of monitoring data, Hsiung [7] suggested a correlation between E and SPT-N as follows: (6) E = 2000 N (kPa) Stroud [19] presented a relationship between E and N values by collecting data from different soils, and he suggested that E decreases as the soil Calculate the corrected SPT values N60 and N160 for a given borehole log. Furthermore, a questionnaire ( Table 5 ) is prepared to collect information on the SPT procedure and equipment so that the reliable corrections and correlations An example profile of measured SPT N-values from a boring by the Vermont Agency of Transportation (VTrans) is presented in Figure 5-3. 9 shows the correlation of bearing capacity value based on SPT-N from boreholes and (c’ and φ). 0 for gravelly sands (E in MPa Sep 14, 2022 · resistance of soil layers is expressed by the number of blows, SPT N-value (N SPT), recorded for the last two 150-mm layers [3]. The cohesion is a term used in describing the shear strength soils. Figure 2 is N m, SPT value measured in the field. 1. 22. 2 is in kN/m or kPa. Civil Engineering questions and answers. 48 – 1. NZ also does have it. The values of N c obtained from [9,10,11] are used in estimating q a. C S. 001 kPa. SPT-N values increase with depth, and a similar trend was also presented by (Din et al. (N 1) 60 = N' x C E x C N x C B x C S x C R x C BF. Mar 7, 2008 · overburden pressure (100 kPa). , unit weight γ, relative Aug 1, 2018 · Also, the cohesion values varied between 5 and 265 kPa. C BF. The clays of the Middle Coal Measures normally are stiff to very stiff and range from intermediate to high plasticity. USCS. 2 N 60 for PI>30, C U (kPa) = 4-5 . Here, the N SPT value does not directly provide the c u value that is used as a geotechnical design parameter. • C E, energy correction factor for the SPT hammer. The undrained shear strength was primarily between 10 and 220 kPa with average value of 127 kPa, which covers fine-grained soil types from very soft to hard with C u mostly corresponding to soft to very stiff soils. f1 = 4. Many correlations between SPT N values and dynamic probing N d are based on comparative field measurements. 1) where soil density (ρ) is the total unit weight of the soil divided by gravity (9. P 0 = over burden pressure, (kPa) = γ x D. These developed The limiting f s = 150 kPa as suggested by the Code is conservative especially for soil with higher SPT ‘N’ value. For piles in coarse grained soils rules of thumb relate shaft friction and end bearing to the SPT N value. Based on the previously stated study, Stroud (1974) proposed a correlation between f 2 and PI for the relation between coefficient of volumetric compression (m v) and SPT-N value as shown in Figure B. 55 (log SPT)-0·26 N = 19 R2 = 0. v/sigma. Jan 31, 2017 · (3) This SPT N-value corresponds to a relative density of approximately 85 percent at an overburden stress of about 2,000 psf (95. N<2. Also, the cohesion values varied between 5 and 265 kPa. I also found that the Flat Dilatometer provided exceedingly good correlations. The Australian code has this correlation. 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 Notably, the unconfined compressive strength ranges from 32. This situation has led many researchers to develop other correlations to predict the c u value using N SPT average value of 90. 0; for trip type donut hammers; C E = 0. c. The wet density relied on moisture content Jul 25, 2006 · In this study the correlations between the SPT-N values and S u values obtained from similar depths are developed by taking account of the fine-grained soil types and SPT-N corrections. The spreadsheet also includes unique analysis tools which Aug 21, 2022 · End Bearing. Computed values of Vs using the Andrus et al. 6 for closed-ended driven pipe piles in sand and C b = 0. 5 for PI>40% and N=5 for PI<40%). 5. 1 newton/square meter = 0. The correlation analysis was conducted for cohesion and number of blows in SPT (SPT-N). This is useful in coarse granular soils where representative or undisturbed samples cannot always be recovered for laboratory testing. 5 N (in kPa)). (Example: A soil with SPT value of 100 may have unit shaft friction of 3x100 = 300 kPa = 44 psi) In design, it is often prudent to impose an upper bound on shaft Dec 4, 2019 · of elasticity value 103 MPa at a pressure of 350 kPa is shown in Fig 6 and 7. Only limited work has been performed to correlate strength of clays from the energy-corrected SPT N-value; N so. depth and E values that were back-analysed, new E – SPT N correlations are established for fill and CDG and they are then verified by field measurements. Example of SPT N-values 5. Empirical relations were developed between cohesion and SPT N value, and between angle of friction and SPT N value (Brown and Hettiarachchi 2008; The data of SPT-N boreholes and (c’ and φ) has been determined by the previous contractor. There have been many attempts by researchers to relate the SPT N value to the CPT cone penetration resistance q c. The Vs values were obtained by the downhole seismic survey. For each case, footing Dec 1, 1996 · In order to take into account the effects of the confining stress on the SPT N-value, the measured N-value was normalized at an effective overburden pressure of 98 kPa (1 kgf/ cm 2) using the equation proposed by Liao and Whitman (1986). (See Fig-2). 3m), CPT (MPa) and sleeve resistance fs (kPa). It is Aug 12, 2008 · SPT is most often used to evaluate the in situ soil properties. Standard penetration test (SPT) N values suggest allowable bearing capacities ranging from 100 to 600 kPa. FRICTION ANGLE FROM SPT VALUES. Unlike the old correlation models only required soil type and N-value to predict Su Jul 3, 2013 · Mccoy (Geotechnical) 3 Jul 13 16:32. • C B, borehole diameter correction. 534 respectively, which indicate reliable The qc values ranged between 1 and 25 MPa. Footing type: 3 feet wide strip footing, bottom of footing at 2 ft below ground surface. Figure 3. Civil Engineering. For soil, the adopted Ks value is 2. where C b = 0. 3 times and generally varies from 3 . 2019; Khalid et al. N 60 (N 1) 60 The standard penetration test is a simple in-situ test in which the N-value is the mumber of blows taken to drive a 50mm diameter bar 300mm into the base of a bore hole. 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. The field tests include the SPTs conducted in the boreholes and the determination of Mar 1, 2020 · In order to take into account the effects of the confining stress on the SPT N-value, the measured N-value was normalized at an effective overburden pressure of 98 kPa (1 kgf/ cm²) using the May 30, 2006 · 3) Correlate DCP readings to SPT values by using acceptable standards. 5–1. 955 (3) Aug 12, 2022 · The empirical correlations for sandy soils proposed by other researchers were also compiled. r=100 KPa =2000 lb/ft2 D/B is the ratio pile embedment depth- diameter N'60 is the normalized value for the SPT, corrected for overburden pressures and field procedures. 8 to 9. D = depth of testing (m) γ = unit weight of soil at the time of testing. 5 for silty sands and by 1. 33* (2/3) = 1. (kPa) = 4. 9 is to see the correlation value between bearing capacity from SPT-N (boreholes) and (c’ and φ). For donut hammers C E = 0. For moderately weathered SIII, high value of f s more than 500 kPa can be May 5, 2019 · SPT conversion to N60 and N1,60. 4) Guess a pad or strip footing width to be used. For p 0 > 75 kPa. SPT N 1 value implies the stress normalized SPT N value that was corrected for an overburden pressure of 100 kPa (1 kgf/cm 2). D. Assume that Em = 60% (i. In this paper, for ease of comparability the super heavy dynamic probing is used friction and end-bearing to standard penetration test (SPT) N values. 015 kPa. 69 Source: Paul Mayne (based on data from VTrans) Figure 5-3. (1. The sum of the number of blows required for the second and third 6 in. 75d above it N s Average SPT N-value along pile shaft O. 057 log10(DCPI60) To know the variation of the CBR value across the depth, draw another semi-log chart with CBR values on logarithmic scale as abscissa (x axis) and depth of penetration on ordinary scale as ordinate (y axis). The modulus of subgrade reaction ks (also called the coefficient of subgrade reaction of soil) is the ratio of the pressure against a flat surface on soil and the settlement at that point. 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 May 1, 2024 · The SPT depth was from 3 to 22 m below ground (mbg), with an average depth of 6. From Jul 1, 2016 · The N-SPT values and Vs values were obtained from the same boreholes between 2005 and 2012. Commonly used ones were given by Poulos (1989) for driven piles qs= 2N and qb= 400N and for bored piles qs= N and qb= 100N ( with all stresses in kPa). Cohesion. 92 MPa and a coefficient of variation of 0. 1 kPa = 1000 newton/square meter. The purpose of plotting the graph in figure 4. Apr 15, 2004 · The measured torque is used along with the known geometry of the split-barrel sampler to determine a value of unit skin friction. Where. Jan 1, 2011 · (kPa) SPT-N Consistency < 25 < 2 Very soft 25 - 50 2- 4 Soft 50 - 100 4 it is in fact possible to estimate the N-SPT value and derive the friction angle from results obtained from 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. SPTCorr provides calculations for both N 60 and Those correlations were presented in Table 5, and they were also plotted in Figure 3 for visual comparison. In most of the correlations, with exception of correlations (Hayati and Andrus, 2009), the independent variable is the ratio q c/Pa/NEr where qc is the cone tip resistance, Pa is a reference pressure of 100 kPa and NEr is SPT N values with Er is the energy ratio of the hammer used in the test. 81 m/sec2 or 32. 5 MPa Nov 3, 2015 · Use the following equation and determine the corresponding CBR value of each layer. Around 40 correlations have been compiled and applied for estimating the shear wave velocity (Vs) correlation for the region and also to address the uncertainty issue. 8–1. 32 MPa to 19. Jul 8, 2017 · where q a is the allowable bearing pressure for a 25-mm settlement, in kPa; D is the footing depth, in m; B is the footing width, in m; and N SPT is the statistical average value of the footing influence zone (from a depth around D − 0. The Nspt-Su correlation is fraught Example 1: Determine soil bearing capacity by SPT numbers (English units) Given. However as N-values measured in clay layer provide rough estimate values only to judge shear strength and softness, they should be carefully considered when actual designs are applied. 13 + 6. Figure 4. g. 4b), in order to reduce the scattered data. Other values I have seen range from 9 to 14 kPa for this type of deposit. N of variation of 1. IJR, in addition to fattdad's sensible analysis, I'd say that given only SPT values in a clay layer you might input the SPT value in correlations which yield Su (cohesion undrained) and use such a value as an input in the bearing capacity formula for undrained conditions. May 13, 2018 · These values of c u are used to estimate q a employing Eq. So, the PP criteria was based actually on N-values. Table 1. 5 to 5 (depends on Plasticity Index - use N=4. (i always use 1m and work backwards during design stage) 5) Use "Peck & Hanson & Thornburn, 1974" chart and 6) Presto you have an allowable bearing pressure!! Guide the top of the remote scale into the scale guide, while lowering the shaft through the bottom guide. For each location, the values of q a are calculated for both strip and square footings, as given in Table 1. The equation for transforming SPT values into CBR values was presented by Livneh and Ishai in 1987 (2) and was then improved in 1988 (5). K = 1+0. So, SPT-N value obtained is lower than actual value. The data also included SPT boring log. Table 2: Relationship among relative density, SPT N value, and internal friction angle of Jun 1, 2004 · This range equates to a multiplier of approximately 11, however much of this range is expected to be due to the extrapolation of the 'N' value from a discontinued SPT -defined either as (a) >30 = Recorded SPT Value N c 15, Nc = NR Correlation in SCPT Test (3) m = mass of cone = 1. This study is based on the results of a comprehensive geotechnical investigation for the Eglinton Crosstown Light Rail Transit (LRT) project in Toronto. Geological profiles and SPT N profiles of the two newly instrumented HA sites (a) KSC; (b) SUK and five past HA sites; (c) HHE; (d) SCR; (e) TTE; (f) CWR and (g) ECW. Use caution to avoid pinching fingers between the hammer and anvil. Feb 1, 2023 · Table 5 shows the correlation between the average unit shaft friction and its corresponding SPT-N value. 5 Correlations between SPT N values and Different Parameters of Soil The SPT has been used to correlate different soil parameters i. 60. As a result, for the SPT-N values ranged from 4 to 44, the predicted soil cohesion and angle of internal of friction increased from 17 kPa to 281 kPa and 4o to 38o respectively. Soil SPT number: 10. (kPa) σ' (kPa) SPT N. The SPT N values are between 2 blows per foot (bpf) and 60 bpf with an average of 23. Su = f1 N (After Stroud and Butler, 1975) N is uncorrected. For TP1 and TP2 granite, adopted parameters for unit shaft friction are 1000 kPa and 10,000 kPa for unit end bearing. 2657, which indicates that there is a poor correlation between equivalent SPT N 60-value and corrected SPT N 60-value. (2012) correlations. research: SPT N (blows/0. 5 mbg. Oct 1, 2017 · Statistical Correlations between undrained shear strength (C U ) and both SPT-N value and net limit pressure (P L ) for cohesive glacial tills. 2 ft/sec2). Requirement: Estimate allowable soil bearing capacity based on. values were derived from SPT-N. Dec 15, 2022 · This difference becomes even greater—1191 kPa—for N-value of 100. The proposed equation was validated using 5 independent values and the estimated values of cohesion based on SPT-N fall in the range of of actual values. 2021). 1 kg m 1 is measured in Kpa As per Schmertman (8) (9) averaged, the chances of mixing the two soil types were Dec 9, 2022 · The linear regression analysis has been performed to develop the correlations for each zone of the soil map to predict the SPT-N value with depth as shown in Table 4 based on its statistics variation shown in Fig 8. The 118 data set shown in Fig. The penetration depth was ranging from 20 mm to 240 mm, with an average value of about 100 mm. N'60= CN*N60 CN= 2/(1+sigma. 70 which shows a moderate correlation. 3. e. For N=1 our UC and Pocket pens were around 10 kPa which sits well with what big H has found. Judgement of Soft ground in Clay by SPT (Terzaghi & Peck, 1948) Consistency N values Unconfined compression strength(qu, kPa) Very Soft < 2 < 25 The average SPT N-value along the pile shaft is commonly utilized in different previous SPT-based correlations with pile skin friction. Similar plot has been adopted by Leung et al. 89 to 472. 5 times the pile diameter above and the same distance below the pile base, and A b is the area more than standard SPT spoon and we get the lower value of SPT. Based on SPT N-value zonation map, Zone-2 is the predominant at the study area comprised of silt and clay soils Consistency SPT-N qu (kPa) Very soft < 2 < 25 Soft 2- 4 25 - 50 Medium 4 - 8 50 - 100 Correcting SPT Blow Counts to N60 Values SPT is not completely standardized considering all the factors Oct 1, 2007 · 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. There are more advanced tools available that provide a better model for the behavior and The results revealed that the corrected SPT N-value (N55) ranged between 3 and 34. 2. Now, after additional field data have been gathered, it is possible to determine the following rec­ ommended expression: log CBR = -5. C N. A guide to get a rough estimation of E in sands is by multiplying N by 0. The SPT, while used less frequently, is still used today. Outside diameter OCR Overconsolidation ratio q p Bearing pressure q limit Limiting point Nov 19, 2003 · The range of values were from 8 to 35 kPa over a depth of 20 metres. C R. Schmertmann (1975) has correlated N-values obtained from SPT tests against effective overburden stress as shown in the figure. (1988). In the stress plane of Shear stress-effective normal stress, the soil cohesion Jan 8, 2008 · Burland & Burbridge method refers mainly to shallow foundations, so I don't know whether it works well with pile problems. 1 Correction Factors Since the introduction of the SPT in 1902, the drop hammer systems have evolved from pin weight to N'60= CN*N60 CN= 2/(1+sigma. 00 Table 6 Relationships between the internal Sep 21, 2017 · Anyways, I expect that the values of unconfined compressive strengths for determining the consistency of clays which you are using, are from correlations from SPT N-values proposed by Terzaghi and Peck(qu = 12. While using the value of N c from , depth factor is also applied. Here, f 2 is a factor depending on plasticity index. 4 MPa to 16. , for estimation of shear wave velocity, bearing capacity etc. Mathematically, this is expressed as; ks = q/δ ——- (1) Where; ks = Coefficient of subgrade reaction expressed in force/length 2 /length. log10CBR = 2. The PMT E 0 value ranges from 2. In estimation of other parameters also, SPT N value is used e. 7106 and 0. (1999) and Hasancebi and Ulusay (2007) utilized corrected N-values for their statistical analysis. 5 P a = 100 kPa; σ′, effective stress of soil at point of measurement. Q1: A standard penetration test SPT was performed on a near surface deposit of clean sand where the number of blows to drive the sampler 45 cm was 5 for the first 15 cm, 8 for the second 15 cm, and 9 for the third 15 cm. C B. 5B up to at least D + 2B), considering an energy ratio of 55%. 1- Complete the consistency of the soil layers based on SPT N-values. Oct 18, 2016 · SPT N value is widely used as it is an index for quick strength characterization due to its simplicity. Its definition is mainly derived from the Mohr-Coulomb failure criterion and it is used to describe the non-frictional part of the shear resitance which is independent of the normal stress. N’ = corrected N value. • C N, overburden correction factor = (P a /σ′) 0. 1): Gmax = ρ · VS 2. c u (kPa) = f 1 x N 60. 88 kPa, and the elastic wave velocity spans 402 to 2000 meters/sec, reinforcing the imperative for a comprehensive and Jun 1, 2009 · Also, the cohesion values varied between 5 and 265 kPa. 3 Feb 21, 2020 · The modification was made by calibrating the V S -N 1;60cs correlation such that the proposed approach for computing K γ yielded a similar value to the laboratory determined value for K σ at σ Dec 1, 2013 · To determine a correlation between SPT N values and dynamic probing N d, it is useful to use the experience accumulated over the years based on SPT N. , En = 0. Pile design based on these average values may involve a degree of uncertainty associated with the possible soil variability along the pile shaft. Solution: Meryerhof's equation. Measured SPT values in the field (N) at each depth (z) will be corrected to (N 1) 60 values using the equation below. The CPT q c values range from 0. Engineering judgment should be used in selecting a specific value. For residual soil with SPT-N > 100, the SPT values in penetration depth over the 100 blows was plotted with elevation (Fig. Connect the upper and lower shafts. In some cases various other factors that influence the SPT results can be taken into consideration when calculating N 1,60 such as bore-hole diameter, rod length e. They tend to be of medium compressibility with undrained shear strengths varying from 50 to 300 kPa. The results also show that the unit skin friction values obtained from the SPT-T generally correlate well with SPT N 60 values. There is an option to specify SPT N values with depth in order to calculate the friction angle for some methods mentioned above. ot bj bx ym vx mv cy jv ou un