{"id":414,"date":"2025-03-31T03:24:11","date_gmt":"2025-03-31T03:24:11","guid":{"rendered":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/example-5-7-design-capacity-from-in-situ-tests-cpt\/"},"modified":"2026-03-16T14:05:45","modified_gmt":"2026-03-16T14:05:45","slug":"example-5-7-design-capacity-from-in-situ-tests-cpt","status":"publish","type":"chapter","link":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/example-5-7-design-capacity-from-in-situ-tests-cpt\/","title":{"raw":"Example 5.7","rendered":"Example 5.7"},"content":{"raw":"Estimate the design capacity of the strip footing shown below according to AS 5100.3-2, directly from CPT measurements. The foundation subsoil is classified as silty sand (SBT=5\/6 from the soil behavior type chart of Figure 1.28<\/a>).\n\n[caption id=\"attachment_413\" align=\"aligncenter\" width=\"700\"]\"The Example 5.7. Problem description and input parameters.[\/caption]\n

Answer:<\/h2>\nThe average cone resistance along a depth z <\/em>= B <\/em>= 4 m below the footing foundation level (-3m) is qc,average<\/sub><\/em> = 4.4 MPa (average of 5 values). Considering conservatively K<\/em>\u03c6<\/sub> = 0.16 as per above, and substituting to Eq. 5.54 yields:\n\n[latex]{q_f} = {K_\\varphi }{q_{c,average}} = 700{\\rm{ \\:kPa}}[\/latex]\n\nNote that the measured cone resistance in this sand is relatively low, and according to Table 1.8 the average N60<\/sub><\/em> value along the influence depth is N60<\/sub><\/em> = (qc,average<\/sub><\/em>\/pa<\/sub><\/em>)\/3.0 = 14.6 therefore the sand is classified as medium dense (Table 1.3).\n\nAs the bearing capacity is determined from CPT test results, the appropriate range of the geotechnical strength reduction factor \u03c6<\/em>g <\/sub>from Table 5.1 is \u03c6<\/em>g <\/sub>= 0.40 to 0.50. Selecting conservatively the lower bound of the proposed range, the design capacity in terms of stress in terms of force per running meter of the strip footing is determined as:\n\n[latex]{\\varphi _g}{q_f} \\ge {S^ * }[\/latex]\n\n[latex]0.40 \\times 700 \\ge {S^ * }[\/latex]\n\n[latex]{S^ * } \\le 280{\\rm{ \\:kPa}}[\/latex]\n\n[latex]{S^ * } \\le 280{\\rm{ \\:kPa}} \\times \\left( {4 \\times 1} \\right){{\\rm{m}}^{\\rm{2}}} = 1120{\\rm{\\:kN}}\/{\\rm{running \\:meter \\:of \\:footing}}[\/latex]","rendered":"

Estimate the design capacity of the strip footing shown below according to AS 5100.3-2, directly from CPT measurements. The foundation subsoil is classified as silty sand (SBT=5\/6 from the soil behavior type chart of Figure 1.28<\/a>).<\/p>\n

\"The
Example 5.7. Problem description and input parameters.<\/figcaption><\/figure>\n

Answer:<\/h2>\n

The average cone resistance along a depth z <\/em>= B <\/em>= 4 m below the footing foundation level (-3m) is qc,average<\/sub><\/em> = 4.4 MPa (average of 5 values). Considering conservatively K<\/em>\u03c6<\/sub> = 0.16 as per above, and substituting to Eq. 5.54 yields:<\/p>\n

[latex]{q_f} = {K_\\varphi }{q_{c,average}} = 700{\\rm{ \\:kPa}}[\/latex]<\/p>\n

Note that the measured cone resistance in this sand is relatively low, and according to Table 1.8 the average N60<\/sub><\/em> value along the influence depth is N60<\/sub><\/em> = (qc,average<\/sub><\/em>\/pa<\/sub><\/em>)\/3.0 = 14.6 therefore the sand is classified as medium dense (Table 1.3).<\/p>\n

As the bearing capacity is determined from CPT test results, the appropriate range of the geotechnical strength reduction factor \u03c6<\/em>g <\/sub>from Table 5.1 is \u03c6<\/em>g <\/sub>= 0.40 to 0.50. Selecting conservatively the lower bound of the proposed range, the design capacity in terms of stress in terms of force per running meter of the strip footing is determined as:<\/p>\n

[latex]{\\varphi _g}{q_f} \\ge {S^ * }[\/latex]<\/p>\n

[latex]0.40 \\times 700 \\ge {S^ * }[\/latex]<\/p>\n

[latex]{S^ * } \\le 280{\\rm{ \\:kPa}}[\/latex]<\/p>\n

[latex]{S^ * } \\le 280{\\rm{ \\:kPa}} \\times \\left( {4 \\times 1} \\right){{\\rm{m}}^{\\rm{2}}} = 1120{\\rm{\\:kN}}\/{\\rm{running \\:meter \\:of \\:footing}}[\/latex]<\/p>\n","protected":false},"author":1,"menu_order":15,"template":"","meta":{"pb_show_title":"","pb_short_title":"Example 5.7","pb_subtitle":"Design capacity from in situ tests: CPT","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-414","chapter","type-chapter","status-publish","hentry"],"part":325,"_links":{"self":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/414","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/414\/revisions"}],"predecessor-version":[{"id":415,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/414\/revisions\/415"}],"part":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/parts\/325"}],"metadata":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/414\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/media?parent=414"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapter-type?post=414"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/contributor?post=414"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/license?post=414"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}