K.S.Gill*,  A.K. Choudhary  **,  J .N.Jha*,S.K.Shukla*** *Guru Nanak Dev Engg. College, Ludhiana,India **National Institut...
<ul><li>Introduction </li></ul><ul><li>Experimental Work </li></ul><ul><li>Field and Laboratory Test </li></ul><ul><li>Tes...
<ul><li>Design of new flexible pavements/ Rehabilitation of existing pavements: </li></ul><ul><li>Needs accurate estimatio...
<ul><li>Insitu California Bearing Ratio (CBR) test: </li></ul><ul><li>Expensive </li></ul><ul><li>Relatively slow to condu...
<ul><li>Laboratory California Bearing Ratio test: </li></ul><ul><li>CBR specimens tested at field mosture content and dens...
<ul><li>Dynamic Cone Penetration </li></ul><ul><li>Light and Portable </li></ul><ul><li>Repeatability is considerably high...
<ul><li>DCP Test conducted : Insitu and soaked conditions </li></ul><ul><li>(Widening and Strengthening of Existing Road) ...
 
<ul><li>Hammer correction factor is unity for 8 kg </li></ul><ul><li>DCP Index(DCPI)or reading is defined as the Penetrati...
<ul><li>DCP test conducted on existing subgrade surface (Three test for each location) </li></ul><ul><li>Number of blows c...
<ul><li>Soaked CBR test:  </li></ul><ul><li>Specimen prepared at insitu density </li></ul><ul><li>Specimen prepared at dif...
 
Chainage (Km) Insitu dry density (kN/m 3  ) Field moisture content (%) Optimum moisture content (%) Maximum dry density (k...
Chainage (Km) Sand content(%) Liquid limit (%) Plasticity Index 4.25 70.0 16.5 NP 5.25 70.0 16.5 NP 6.25 68.5 17.0 NP 7.25...
Chainage (Km) Soaked Lab CBR  at insitu density (%) Insitu CBR (%) based on DCPT Soaked insitu CBR (%) based on DCPT Insit...
<ul><li>Variation of CBR under different condition is expressed by a term CBRI defined by  </li></ul><ul><li>CBRI 1 =CBR L...
 
<ul><li>Compaction level :%age compaction in the field with respect to the maximum dry density.  </li></ul><ul><li>Y=0.000...
 
 
<ul><li>The CBR value of uniform soils having  similar characteristics  can be determined quickly and  with  adequate accu...
<ul><li>Similarly laboratory soaked CBR value can be evaluated after establishing a correlation between CBRI  </li></ul><u...
<ul><li>Thankyou .......................... </li></ul>
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Estimation of CBR value using Dynamic Cone Penetrometer

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The subbase/base thickness of pavement is governed by the CBR value of the subgrade soil along with some other parameters such as traffic intensity, climatic conditions, etc. Dynamic cone penetration test (DCPT) value conducted in the field can be used to estimate the CBR value provided a suitable relationship exists between CBR and DCPT value.

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Estimation of CBR value using Dynamic Cone Penetrometer

  1. 1. K.S.Gill*, A.K. Choudhary **, J .N.Jha*,S.K.Shukla*** *Guru Nanak Dev Engg. College, Ludhiana,India **National Institute of Technology, Jamshedpur, India ***School of Engineering,Edith Cowan University,Perth Australia
  2. 2. <ul><li>Introduction </li></ul><ul><li>Experimental Work </li></ul><ul><li>Field and Laboratory Test </li></ul><ul><li>Test Procedure and sample preparation </li></ul><ul><li>Result and Discussion </li></ul><ul><li>Conclusions </li></ul><ul><li>References </li></ul>
  3. 3. <ul><li>Design of new flexible pavements/ Rehabilitation of existing pavements: </li></ul><ul><li>Needs accurate estimation of CBR </li></ul><ul><li>Requires simulation of worst possible environmental condition to be faced by </li></ul><ul><li>by highway during its design life </li></ul>
  4. 4. <ul><li>Insitu California Bearing Ratio (CBR) test: </li></ul><ul><li>Expensive </li></ul><ul><li>Relatively slow to conduct </li></ul><ul><li>Difficult to conduct insitu soaked CBR test </li></ul><ul><li>Misleading results obtained if piston tip rests on small stone particle or pebbles </li></ul><ul><li>Repeatibility of result doubtful </li></ul>
  5. 5. <ul><li>Laboratory California Bearing Ratio test: </li></ul><ul><li>CBR specimens tested at field mosture content and density tend to give higher CBR value in laboratory than those obtained in the field (particularly for granular soil) </li></ul><ul><li>Difference is due to the confining effect of rigid mould in laboratory tests </li></ul><ul><li>Highway Engineers generally donot favour CBR tests </li></ul>
  6. 6. <ul><li>Dynamic Cone Penetration </li></ul><ul><li>Light and Portable </li></ul><ul><li>Repeatability is considerably higher </li></ul><ul><li>Suitable co-relation if developed between DCPT and CBR value can offer an attractive means of determining insitu CBR at a comparative speed and ease of operation </li></ul>
  7. 7. <ul><li>DCP Test conducted : Insitu and soaked conditions </li></ul><ul><li>(Widening and Strengthening of Existing Road) </li></ul><ul><li>8 km Stretch of the left bank of Sidhwan Canal passing through sotheren part of Ludhiana city </li></ul><ul><li>8 locations marked at an interval of 1 km </li></ul><ul><li>Laboratory soaked CBR tests on the specimen moulded at insitu density </li></ul>
  8. 9. <ul><li>Hammer correction factor is unity for 8 kg </li></ul><ul><li>DCP Index(DCPI)or reading is defined as the Penetration depth in mm per a single drop of hammer </li></ul><ul><li>Depth of penetration in the present case is 800mm </li></ul><ul><li>Stress induced due to wheel load becomes negligible beyond this depth </li></ul>
  9. 10. <ul><li>DCP test conducted on existing subgrade surface (Three test for each location) </li></ul><ul><li>Number of blows counted for 800mm penetration </li></ul><ul><li>Soil resistance = Penetration (mm)/Blow </li></ul><ul><li>Penetration for first blow is discounted since the imprint area of cone tip for the first blow smaller than that of subsequent blows </li></ul><ul><li>Soaked Insitu DCP test : Conducted during Monsoon </li></ul>
  10. 11. <ul><li>Soaked CBR test: </li></ul><ul><li>Specimen prepared at insitu density </li></ul><ul><li>Specimen prepared at different compaction level by varying number of blows </li></ul><ul><li>No. of blows selected= 15, 25, 35, 65 </li></ul>
  11. 13. Chainage (Km) Insitu dry density (kN/m 3 ) Field moisture content (%) Optimum moisture content (%) Maximum dry density (kN/m 3 ) Compaction Level 4.25 19.20 2.4 9.5 19.70 97.46 5.25 18.80 3.2 9.5 19.70 95.43 6.25 17.55 3.4 9.6 19.55 89.76 7.25 16.95 3.8 9.6 19.50 86.92 8.25 18.50 2.9 9.6 19.50 94.87 9.25 18.00 3.1 9.4 19.75 91.13 10.25 16.85 3.9 9.5 19.55 86.18 11.25 16.80 3.9 9.5 19.60 85.71
  12. 14. Chainage (Km) Sand content(%) Liquid limit (%) Plasticity Index 4.25 70.0 16.5 NP 5.25 70.0 16.5 NP 6.25 68.5 17.0 NP 7.25 68.0 17.0 NP 8.25 66.5 17.2 NP 9.25 64.5 17.7 NP 10.25 65.0 17.5 NP 11.25 63.5 17.9 NP
  13. 15. Chainage (Km) Soaked Lab CBR at insitu density (%) Insitu CBR (%) based on DCPT Soaked insitu CBR (%) based on DCPT Insitu DCPI (mm/Blow) 4.25 10.94 14.40 7.20 14.70 5.25 10.59 13.50 6.75 15.55 6.25 8.95 12.10 5.87 17.15 7.25 8.50 10.80 5.40 19.00 8.25 9.94 13.24 6.68 15.83 9.25 10.12 12.95 6.41 16.20 10.25 7.61 10.24 5.09 19.90 11.25 7.61 10.20 5.07 19.98
  14. 16. <ul><li>Variation of CBR under different condition is expressed by a term CBRI defined by </li></ul><ul><li>CBRI 1 =CBR LS / CBR DCPS </li></ul><ul><li>CBRI 2 =CBR DCP /CBR DCPS </li></ul><ul><li>Where CBR LS is the laboratory soaked CBR value at in situ density </li></ul><ul><li>CBR DCP is DCP based in-situ CBR value at field moisture content and in-situ density and </li></ul><ul><li>CBR DPCS is the DCP based in situ CBR value under soaked condition. </li></ul>
  15. 18. <ul><li>Compaction level :%age compaction in the field with respect to the maximum dry density. </li></ul><ul><li>Y=0.0007x+1.4646 </li></ul><ul><li>Y= -0.0015x+2.1465 </li></ul><ul><li>X= compaction level </li></ul><ul><li>Y= CBRI </li></ul>
  16. 21. <ul><li>The CBR value of uniform soils having similar characteristics can be determined quickly and with adequate accuracy using the DCPT results. </li></ul><ul><li>Once the correlation is established between CBRI and compaction level or in-situ density for tests conducted under different conditions, soaked CBR value in the field can be determined very quickly by conducting the in-situ DCPT for existing conditions and using the CBRI value for that particular condition. </li></ul><ul><li>  </li></ul>
  17. 22. <ul><li>Similarly laboratory soaked CBR value can be evaluated after establishing a correlation between CBRI </li></ul><ul><li> ( CBR LS / CBR DCPS ) and compaction level . </li></ul><ul><li>For construction of new embankments or strengthening of existing pavements, DCPT will be a very useful tool for evaluating the strength of sub grade in terms of CBR value. </li></ul><ul><li>It may helpful in enhancing highway construction quality control, ensuring long-term pavement performance, stabilityand achieving more uniform structural property. </li></ul>
  18. 23. <ul><li>Thankyou .......................... </li></ul>

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