{"id":43,"date":"2024-12-03T00:12:41","date_gmt":"2024-12-03T00:12:41","guid":{"rendered":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/1-4-boreholes-and-sampling-methods\/"},"modified":"2026-03-16T13:51:45","modified_gmt":"2026-03-16T13:51:45","slug":"1-4-boreholes-and-sampling-methods","status":"publish","type":"chapter","link":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/chapter\/1-4-boreholes-and-sampling-methods\/","title":{"raw":"1.4 Boreholes and sampling methods","rendered":"1.4 Boreholes and sampling methods"},"content":{"raw":"Sampling boreholes are a critical part of any geotechnical investigation campaign. They are performed to:\n<ul>\n \t<li>Identify the distribution of geomaterials with distinctive properties into the subsoil, including the presence and thickness of layers.<\/li>\n \t<li>Retrieve samples for laboratory tests.<\/li>\n \t<li>Determine the depth of the groundwater table, through installation of piezometers.<\/li>\n \t<li>Provide access for the introduction of <em>in-situ <\/em>testing devices.<\/li>\n<\/ul>\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"714\"]<img class=\"size-full wp-image-33\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost.png\" alt=\"Graph depicting the relationship between geotechnical investigation costs, project impact, and total costs. Relationships are graded from red on the extreme left to grey on the right, with the optimal range (centre) highlighted in green.\" width=\"714\" height=\"498\"> Figure 1.3. Effect of soil investigation on potential projects costs.[\/caption]\n\n&nbsp;\n<table class=\"grid aligncenter\" style=\"border-collapse: collapse;width: 100%\" border=\"0\"><caption><strong>Table 1.2.<\/strong>Minimum number and depth of borings, for different (geo)structures (with information from Gunaratne 2006 and FHWA 2002).<\/caption>\n<tbody>\n<tr>\n<th style=\"width: 33.3333%;text-align: center\">(Geo)structure type<\/th>\n<th style=\"width: 33.3333%;text-align: center\">Minimum number of sampling boreholes<\/th>\n<th style=\"width: 33.3333%;text-align: center\">Minimum depth of sampling boreholes<\/th>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Structural foundations<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One per substructure unit for width \u2264 30 m<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Advance boreholes: (1) Through unsuitable foundations soils e.g., peat, highly organic soils, soft fine-grained soils, uncontrolled fills into competent material of suitable bearing capacity (2) to a depth where stress increase due to external footing loading is less than 10% of existing effective vertical stress (see Part 3) or (3) a minimum of 3 m into bedrock, if bedrock is encountered at shallower depth<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Retaining systems<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Two per substructure unit for width &gt; 30 m. Boreholes should be alternatively spaced every 30 m to 60 m in front of and behind wall<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Advance boreholes to a depth of time times the retained height, or a minimum of 3 m into bedrock<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Culverts<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Two boreholes, depending on length<\/td>\n<td style=\"width: 33.3333%;text-align: center\">See structural foundations<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Bridge approach embankments founded on soft soils<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One borehole at each embankment location, to address issues associated with stability, settlement, negative skin friction, lateral pressure on bridge pile foundations.<\/td>\n<td style=\"width: 33.3333%;text-align: center\">See structural foundations. Additional shallow boreholes (trial pits) are an economical means to determine depth of unsuitable surface foundation soils<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Earthworks (cuts and embankments)<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One borehole every 60 m (erratic conditions) to 150 m (uniform conditions). For high cuts and fills (e.g. 10 m), two boreholes along a straight line perpendicular to centerline or planned slope face, to establish an appropriate cross-section for stability analysis<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Cuts: (1) In stable materials, advance boreholes a minimum of 3 to 5 m below cut grade. (2) In soft\/problematic soils, advance boreholes below cut grade to firm materials, or to the height of the cut below grade, whichever occurs first. Embankment: Advance boreholes to firm material, or to depth twice the embankment height, whichever occurs first<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n&nbsp;\n<p class=\"import-Normal\">Many types of equipment and soil boring techniques are used in practice, and describing them in detail is beyond the scope of this Part. Only an overview of most common methods is provided in the following. Auger borings are commonly used for boring through soil formations (Day 1999, FHWA 2006). An auger is an apparatus with a helical shaft that is manually or, most commonly, mechanically advanced to drill a hole into soil by applying downwards pressure. The auger may be continuous, where the helix extends along the entire length of the shaft, or for shallow boreholes, discontinuous (single flight) where the auger helix is at the bottom of the drill stem (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.4-continuous-flight-auger.png\">Figure 1.4<\/a>).<\/p>\n<p class=\"import-Normal\">There are two types of continuous flight augers: solid stem and hollow stem (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.5-hollow-and-solid-stem-auger.png\">Figure 1.5<\/a>). The solid stem must be periodically removed from the borehole to allow retrieving soil samples. A hollow stem auger has a circular hollow core that allows for sampling through the center of the auger, which acts like casing to facilitate sampling in loose\/soft soils under the groundwater table.<\/p>\n\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"1038\"]<img class=\"size-full wp-image-34\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger.png\" alt=\"Photographs of large diameter auger on the left, and small diameter auger on the right. The large diameter auger is in close-up, positioned vertically just over the borehole. The small diameter auger is attached to the rig, moving into or out of the borehole. There is a man in a hi-vis vest and hard hat next to the rig watching the operation. There are two more small diameter augers lying on the ground close to the borehole.\" width=\"1038\" height=\"631\"> Figure 1.4.\u00a0Large and small diameter continuous flight auger (FHWA 2006, U.S. Govt copyright).[\/caption]\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"1145\"]<img class=\"size-full wp-image-35\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger.png\" alt=\"The photo on the left shows a solid stem auger lying next to a hollow stem auger. The solid stem auger shows a core with a small hole in the end, while the hollow stem auger shows a hole the width of the inner shaft. The photo on the right shows blue cutting teeth on the end of a hollow stem auger, next to a plug which is a rod with attachments on each end.\" width=\"1145\" height=\"450\"> Figure 1.5. (Left) Hollow and solid stem auger, and (Right) Outer and inner assembly of a hollow stem auger (FHWA 2006, U.S. Govt copyright).[\/caption]\n<p class=\"import-Normal\">If relatively stiff\/hard formations are encountered, a water-circulation system is used, that aids cutting and drawing the material to the surface <em>(wash boring-<\/em><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.6-wash-boring-drill-rig.png\">Figure 1.6<\/a><em>). <\/em>Casings are often used to prevent cave-in of the borehole. Casing of the borehole may require additional time and effort, but will result in a protected borehole, where monitoring instruments can be installed e.g., a piezometer to measure groundwater table level fluctuations, or an inclinometer for measure possible lateral soil movements.<\/p>\n<p class=\"import-Normal\">When drilling through generally stiff formations, rotary coring is used (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\">Figure 1.7<\/a>) to retrieve intact core samples. Power rotation of the drilling bit is accompanied by the introduction of a circulating fluid to remove cuttings from the hole.<\/p>\n<p class=\"import-Normal\">Besides the methods described above, which are the ones typically used in practice, a plethora of other methods are also used for boring through soils and rocks e.g. bucket auger boring, Becker hammer penetration, percussion drilling, sonic drilling etc.<\/p>\n\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"742\"]<img class=\"size-full wp-image-36\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig.png\" alt=\"Vertical cross-section of a wash boring drill rig showing all parts above and below the ground.\" width=\"742\" height=\"651\"> Figure 1.6. Schematic of a wash boring drill rig (FHWA 2006, U.S. Govt copyright).[\/caption]\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"1190\"]<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\"><img class=\"wp-image-37 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core.png\" alt=\"The photo on the left shows an orange drill rig with an operator on the elevated platform. The rig stands on bare ground and there are spare parts lying near it. The photo on the right shows four core samples lying beside each other on the ground.\" width=\"1190\" height=\"513\"><\/a> Figure 1.7. (a) Rotary drilling in action, and (b) Borehole core and undisturbed sample retrieved to surface (author's own photos).[\/caption]\n\nWhen the borehole core is retrieved to surface (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\">Figure 1.7b<\/a>), a qualified person e.g., a geologist should observe the type, texture and color of the soil retrieved from different depths, and fill in a <em>borehole log <\/em>with all the information (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.8-borehole-log.png\">Figure 1.8<\/a>).\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"884\"]<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.8-borehole-log.png\"><img class=\"wp-image-38 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log.png\" alt=\"The table has space at the top for the project name, location and elevation. Then the table begins, with five columns titled 'Depth (m)', 'sample', 'water level', 'graphic' and 'description'. The 'depth' column has 20 rows, numbered 1 to 20. the 'sample' column contains the initials 'D' or 'SPT' depending on the type of sample. Water level is 11.95m for all samples. The 'graphic' column contains a different colour for each sample described. The descriptions are: '2.60 m - Dark gray, fine to medium sand, medium dense with subangular gravels'; '5.10 m - Brown clayey silt, firm, with a few gravels'; '7.35 m - Brown, firm sandy clay'; '11.20 m - Cobbles and gravels with a few dark brown sand. Between 10.20m and 10.60m a layer of brown, fine clayey sand'; '16.05 m - Black gray, very soft to soft, sandy-clayey silt. Between 15.10m and 15.30m a layer of silty organic sand'; and '20.00 m - Black gray, locally blue gray dense fine silty sand'. At the bottom of the table is a note: 'End of borehole at 20.0 m'.\" width=\"884\" height=\"628\"><\/a> Figure 1.8. Typical borehole log with information filled on site.[\/caption]\n<p class=\"import-Normal\">As far as the method used to retrieve soil samples to the surface is concerned, there are two main categories of soil sampling techniques: <em>d<\/em><em>isturbed <\/em><em>s<\/em><em>ampling<\/em> and <em>u<\/em><em>ndisturbed <\/em><em>s<\/em><em>ampling<\/em><em>.<\/em><\/p>\n<p class=\"import-Normal\">Disturbed sampling of soil provides the means to evaluate soil stratigraphy by visual examination, and soil specimens for laboratory index determination or testing of remolded samples. Disturbed samples are usually collected using split-barrel samplers (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.9-split-barrel-sampler.png\">Figure 1.9<\/a>). Shallow disturbed samples can be also obtained by using hand augers or from test pits.<\/p>\n&nbsp;\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"1002\"]<img class=\"size-full wp-image-39\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler.png\" alt=\"A barrel split into two horizontal halves, the half closer to the camera showing a sample core at the end. The barrel lies next to a tape measure.\" width=\"1002\" height=\"281\"> Figure 1.9. Split barrel sampler for retrieving disturbed samples (FHWA 2006, U.S. Govt copyright).[\/caption]\n<p class=\"import-Normal\">Undisturbed, high-quality, soil samples on the other hand are required for performing laboratory shear strength and consolidation tests on soft to stiff fine-grained soils. In reality, it is impossible to collect truly undisturbed soil samples, as soil stress changes upon sampling and retrieving the sample to surface. The goal of undisturbed sampling is to minimise alteration of the soil structure, changes in the moisture content or the void ratio, and changes in the chemical composition of the soil. Various methods are used for undisturbed soil sampling, ranging from simple cost-effecting methods (which however induce significant disturbance during sampling), as the thin-walled Shelby tube (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.10-tube-samplers.png\">Figure 1.10a<\/a>), up to extremely costly methods (e.g. soil freezing) used only in special projects.<\/p>\n<p class=\"import-Normal\">As illustrated in <a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.11-CT-scan-of-shelby-tube.png\">Figure 1.11<\/a> thought, sampling even with the more advanced fixed-piston sampler (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.10-tube-samplers.png\">Figure 1.10b<\/a>) with diameter 50 mm to 100 mm will result in some soil disturbance, particularly at the top and bottom parts of the sample. As the soil fabric is disturbed, laboratory test results may be compromised, and this must be properly considered when interpreting laboratory test results to retrieve soil parameters. More advanced sampling tools, such as mini-block sampler used in the University of Newcastle (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.12-mini-block-sampler.png\">Figure 1.12<\/a>) will produce soil samples of optimum quality for laboratory testing.<\/p>\n\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"1105\"]<img class=\"size-full wp-image-40\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers.png\" alt=\"A small photo on the left (image (a)) shows a metal rod, coppery in colour, with a yellow plastic cap at each end. Image (b) shows three vertical cross-sections of the Osterberg composite hydraulic sampler from top to bottom, ending with an image of the enclosed sampler barrel on the far right.\" width=\"1105\" height=\"754\"> Figure 1.10. (a) Thin-walled Shelby tube sampler (FHWA 2006, U.S. Govt copyright) and (b) Osterberg composite hydraulic fixed-piston sampler for retrieving high-quality undisturbed samples (da Fonseca and Pineda 2017, reproduced with permission).[\/caption]\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"954\"]<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.11-CT-scan-of-shelby-tube.png\"><img class=\"wp-image-41 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube.png\" alt=\"Two CT scan images, one above the other. The top image has four areas of the sample outlined with red rectangles. The bottom image has two areas, one of the far left and one on the far right, outlined with red rectangles.\" width=\"954\" height=\"429\"><\/a> Figure 1.11. CT-scan of 75 mm-diameter Shelby tube (top) and 89 mm-diameter fixed-piston (bottom) samples (Pineda et al. 2016, reproduced with permission).[\/caption]\n\n[caption id=\"attachment_40\" align=\"aligncenter\" width=\"678\"]<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.12-mini-block-sampler.png\"><img class=\"wp-image-42 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler.png\" alt=\"The photo on the left shows a hollow cylindrical metal frame sitting on office carpet, with a shaft in the top centre. The photo on the right shows a solid cylindrical block of clay sitting on wet ground near a sampling rig.\" width=\"678\" height=\"448\"><\/a> Figure 1.12. University of Newcastle mini-block sampler and block sample of soft silty clay (author's own photos).[\/caption]","rendered":"<p>Sampling boreholes are a critical part of any geotechnical investigation campaign. They are performed to:<\/p>\n<ul>\n<li>Identify the distribution of geomaterials with distinctive properties into the subsoil, including the presence and thickness of layers.<\/li>\n<li>Retrieve samples for laboratory tests.<\/li>\n<li>Determine the depth of the groundwater table, through installation of piezometers.<\/li>\n<li>Provide access for the introduction of <em>in-situ <\/em>testing devices.<\/li>\n<\/ul>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 714px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-33\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost.png\" alt=\"Graph depicting the relationship between geotechnical investigation costs, project impact, and total costs. Relationships are graded from red on the extreme left to grey on the right, with the optimal range (centre) highlighted in green.\" width=\"714\" height=\"498\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost.png 714w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost-300x209.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost-65x45.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost-225x157.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2024\/12\/1.3-effect-of-soil-investigation-on-final-cost-350x244.png 350w\" sizes=\"(max-width: 714px) 100vw, 714px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.3. Effect of soil investigation on potential projects costs.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<table class=\"grid aligncenter\" style=\"border-collapse: collapse;width: 100%\">\n<caption><strong>Table 1.2.<\/strong>Minimum number and depth of borings, for different (geo)structures (with information from Gunaratne 2006 and FHWA 2002).<\/caption>\n<tbody>\n<tr>\n<th style=\"width: 33.3333%;text-align: center\">(Geo)structure type<\/th>\n<th style=\"width: 33.3333%;text-align: center\">Minimum number of sampling boreholes<\/th>\n<th style=\"width: 33.3333%;text-align: center\">Minimum depth of sampling boreholes<\/th>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Structural foundations<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One per substructure unit for width \u2264 30 m<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Advance boreholes: (1) Through unsuitable foundations soils e.g., peat, highly organic soils, soft fine-grained soils, uncontrolled fills into competent material of suitable bearing capacity (2) to a depth where stress increase due to external footing loading is less than 10% of existing effective vertical stress (see Part 3) or (3) a minimum of 3 m into bedrock, if bedrock is encountered at shallower depth<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Retaining systems<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Two per substructure unit for width &gt; 30 m. Boreholes should be alternatively spaced every 30 m to 60 m in front of and behind wall<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Advance boreholes to a depth of time times the retained height, or a minimum of 3 m into bedrock<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Culverts<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Two boreholes, depending on length<\/td>\n<td style=\"width: 33.3333%;text-align: center\">See structural foundations<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Bridge approach embankments founded on soft soils<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One borehole at each embankment location, to address issues associated with stability, settlement, negative skin friction, lateral pressure on bridge pile foundations.<\/td>\n<td style=\"width: 33.3333%;text-align: center\">See structural foundations. Additional shallow boreholes (trial pits) are an economical means to determine depth of unsuitable surface foundation soils<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%;text-align: center\">Earthworks (cuts and embankments)<\/td>\n<td style=\"width: 33.3333%;text-align: center\">One borehole every 60 m (erratic conditions) to 150 m (uniform conditions). For high cuts and fills (e.g. 10 m), two boreholes along a straight line perpendicular to centerline or planned slope face, to establish an appropriate cross-section for stability analysis<\/td>\n<td style=\"width: 33.3333%;text-align: center\">Cuts: (1) In stable materials, advance boreholes a minimum of 3 to 5 m below cut grade. (2) In soft\/problematic soils, advance boreholes below cut grade to firm materials, or to the height of the cut below grade, whichever occurs first. Embankment: Advance boreholes to firm material, or to depth twice the embankment height, whichever occurs first<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p class=\"import-Normal\">Many types of equipment and soil boring techniques are used in practice, and describing them in detail is beyond the scope of this Part. Only an overview of most common methods is provided in the following. Auger borings are commonly used for boring through soil formations (Day 1999, FHWA 2006). An auger is an apparatus with a helical shaft that is manually or, most commonly, mechanically advanced to drill a hole into soil by applying downwards pressure. The auger may be continuous, where the helix extends along the entire length of the shaft, or for shallow boreholes, discontinuous (single flight) where the auger helix is at the bottom of the drill stem (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.4-continuous-flight-auger.png\">Figure 1.4<\/a>).<\/p>\n<p class=\"import-Normal\">There are two types of continuous flight augers: solid stem and hollow stem (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.5-hollow-and-solid-stem-auger.png\">Figure 1.5<\/a>). The solid stem must be periodically removed from the borehole to allow retrieving soil samples. A hollow stem auger has a circular hollow core that allows for sampling through the center of the auger, which acts like casing to facilitate sampling in loose\/soft soils under the groundwater table.<\/p>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 1038px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-34\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger.png\" alt=\"Photographs of large diameter auger on the left, and small diameter auger on the right. The large diameter auger is in close-up, positioned vertically just over the borehole. The small diameter auger is attached to the rig, moving into or out of the borehole. There is a man in a hi-vis vest and hard hat next to the rig watching the operation. There are two more small diameter augers lying on the ground close to the borehole.\" width=\"1038\" height=\"631\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger.png 1038w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-300x182.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-1024x622.png 1024w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-768x467.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-65x40.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-225x137.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.4-continuous-flight-auger-350x213.png 350w\" sizes=\"(max-width: 1038px) 100vw, 1038px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.4.\u00a0Large and small diameter continuous flight auger (FHWA 2006, U.S. Govt copyright).<\/figcaption><\/figure>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 1145px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-35\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger.png\" alt=\"The photo on the left shows a solid stem auger lying next to a hollow stem auger. The solid stem auger shows a core with a small hole in the end, while the hollow stem auger shows a hole the width of the inner shaft. The photo on the right shows blue cutting teeth on the end of a hollow stem auger, next to a plug which is a rod with attachments on each end.\" width=\"1145\" height=\"450\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger.png 1145w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-300x118.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-1024x402.png 1024w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-768x302.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-65x26.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-225x88.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.5-hollow-and-solid-stem-auger-350x138.png 350w\" sizes=\"(max-width: 1145px) 100vw, 1145px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.5. (Left) Hollow and solid stem auger, and (Right) Outer and inner assembly of a hollow stem auger (FHWA 2006, U.S. Govt copyright).<\/figcaption><\/figure>\n<p class=\"import-Normal\">If relatively stiff\/hard formations are encountered, a water-circulation system is used, that aids cutting and drawing the material to the surface <em>(wash boring-<\/em><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.6-wash-boring-drill-rig.png\">Figure 1.6<\/a><em>). <\/em>Casings are often used to prevent cave-in of the borehole. Casing of the borehole may require additional time and effort, but will result in a protected borehole, where monitoring instruments can be installed e.g., a piezometer to measure groundwater table level fluctuations, or an inclinometer for measure possible lateral soil movements.<\/p>\n<p class=\"import-Normal\">When drilling through generally stiff formations, rotary coring is used (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\">Figure 1.7<\/a>) to retrieve intact core samples. Power rotation of the drilling bit is accompanied by the introduction of a circulating fluid to remove cuttings from the hole.<\/p>\n<p class=\"import-Normal\">Besides the methods described above, which are the ones typically used in practice, a plethora of other methods are also used for boring through soils and rocks e.g. bucket auger boring, Becker hammer penetration, percussion drilling, sonic drilling etc.<\/p>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 742px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-36\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig.png\" alt=\"Vertical cross-section of a wash boring drill rig showing all parts above and below the ground.\" width=\"742\" height=\"651\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig.png 742w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig-300x263.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig-65x57.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig-225x197.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.6-wash-boring-drill-rig-350x307.png 350w\" sizes=\"(max-width: 742px) 100vw, 742px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.6. Schematic of a wash boring drill rig (FHWA 2006, U.S. Govt copyright).<\/figcaption><\/figure>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 1190px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\"><img decoding=\"async\" class=\"wp-image-37 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core.png\" alt=\"The photo on the left shows an orange drill rig with an operator on the elevated platform. The rig stands on bare ground and there are spare parts lying near it. The photo on the right shows four core samples lying beside each other on the ground.\" width=\"1190\" height=\"513\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core.png 1190w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-300x129.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-1024x441.png 1024w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-768x331.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-65x28.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-225x97.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.7-rotary-drilling-and-borehole-core-350x151.png 350w\" sizes=\"(max-width: 1190px) 100vw, 1190px\" \/><\/a><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.7. (a) Rotary drilling in action, and (b) Borehole core and undisturbed sample retrieved to surface (author&#8217;s own photos).<\/figcaption><\/figure>\n<p>When the borehole core is retrieved to surface (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.7-rotary-drilling-and-borehole-core.png\">Figure 1.7b<\/a>), a qualified person e.g., a geologist should observe the type, texture and color of the soil retrieved from different depths, and fill in a <em>borehole log <\/em>with all the information (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.8-borehole-log.png\">Figure 1.8<\/a>).<\/p>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 884px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.8-borehole-log.png\"><img decoding=\"async\" class=\"wp-image-38 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log.png\" alt=\"The table has space at the top for the project name, location and elevation. Then the table begins, with five columns titled 'Depth (m)', 'sample', 'water level', 'graphic' and 'description'. The 'depth' column has 20 rows, numbered 1 to 20. the 'sample' column contains the initials 'D' or 'SPT' depending on the type of sample. Water level is 11.95m for all samples. The 'graphic' column contains a different colour for each sample described. The descriptions are: '2.60 m - Dark gray, fine to medium sand, medium dense with subangular gravels'; '5.10 m - Brown clayey silt, firm, with a few gravels'; '7.35 m - Brown, firm sandy clay'; '11.20 m - Cobbles and gravels with a few dark brown sand. Between 10.20m and 10.60m a layer of brown, fine clayey sand'; '16.05 m - Black gray, very soft to soft, sandy-clayey silt. Between 15.10m and 15.30m a layer of silty organic sand'; and '20.00 m - Black gray, locally blue gray dense fine silty sand'. At the bottom of the table is a note: 'End of borehole at 20.0 m'.\" width=\"884\" height=\"628\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log.png 884w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log-300x213.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log-768x546.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log-65x46.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log-225x160.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.8-borehole-log-350x249.png 350w\" sizes=\"(max-width: 884px) 100vw, 884px\" \/><\/a><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.8. Typical borehole log with information filled on site.<\/figcaption><\/figure>\n<p class=\"import-Normal\">As far as the method used to retrieve soil samples to the surface is concerned, there are two main categories of soil sampling techniques: <em>d<\/em><em>isturbed <\/em><em>s<\/em><em>ampling<\/em> and <em>u<\/em><em>ndisturbed <\/em><em>s<\/em><em>ampling<\/em><em>.<\/em><\/p>\n<p class=\"import-Normal\">Disturbed sampling of soil provides the means to evaluate soil stratigraphy by visual examination, and soil specimens for laboratory index determination or testing of remolded samples. Disturbed samples are usually collected using split-barrel samplers (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.9-split-barrel-sampler.png\">Figure 1.9<\/a>). Shallow disturbed samples can be also obtained by using hand augers or from test pits.<\/p>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 1002px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-39\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler.png\" alt=\"A barrel split into two horizontal halves, the half closer to the camera showing a sample core at the end. The barrel lies next to a tape measure.\" width=\"1002\" height=\"281\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler.png 1002w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler-300x84.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler-768x215.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler-65x18.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler-225x63.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.9-split-barrel-sampler-350x98.png 350w\" sizes=\"(max-width: 1002px) 100vw, 1002px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.9. Split barrel sampler for retrieving disturbed samples (FHWA 2006, U.S. Govt copyright).<\/figcaption><\/figure>\n<p class=\"import-Normal\">Undisturbed, high-quality, soil samples on the other hand are required for performing laboratory shear strength and consolidation tests on soft to stiff fine-grained soils. In reality, it is impossible to collect truly undisturbed soil samples, as soil stress changes upon sampling and retrieving the sample to surface. The goal of undisturbed sampling is to minimise alteration of the soil structure, changes in the moisture content or the void ratio, and changes in the chemical composition of the soil. Various methods are used for undisturbed soil sampling, ranging from simple cost-effecting methods (which however induce significant disturbance during sampling), as the thin-walled Shelby tube (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.10-tube-samplers.png\">Figure 1.10a<\/a>), up to extremely costly methods (e.g. soil freezing) used only in special projects.<\/p>\n<p class=\"import-Normal\">As illustrated in <a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.11-CT-scan-of-shelby-tube.png\">Figure 1.11<\/a> thought, sampling even with the more advanced fixed-piston sampler (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.10-tube-samplers.png\">Figure 1.10b<\/a>) with diameter 50 mm to 100 mm will result in some soil disturbance, particularly at the top and bottom parts of the sample. As the soil fabric is disturbed, laboratory test results may be compromised, and this must be properly considered when interpreting laboratory test results to retrieve soil parameters. More advanced sampling tools, such as mini-block sampler used in the University of Newcastle (<a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.12-mini-block-sampler.png\">Figure 1.12<\/a>) will produce soil samples of optimum quality for laboratory testing.<\/p>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 1105px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-40\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers.png\" alt=\"A small photo on the left (image (a)) shows a metal rod, coppery in colour, with a yellow plastic cap at each end. Image (b) shows three vertical cross-sections of the Osterberg composite hydraulic sampler from top to bottom, ending with an image of the enclosed sampler barrel on the far right.\" width=\"1105\" height=\"754\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers.png 1105w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-300x205.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-1024x699.png 1024w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-768x524.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-65x44.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-225x154.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.10-tube-samplers-350x239.png 350w\" sizes=\"(max-width: 1105px) 100vw, 1105px\" \/><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.10. (a) Thin-walled Shelby tube sampler (FHWA 2006, U.S. Govt copyright) and (b) Osterberg composite hydraulic fixed-piston sampler for retrieving high-quality undisturbed samples (da Fonseca and Pineda 2017, reproduced with permission).<\/figcaption><\/figure>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 954px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.11-CT-scan-of-shelby-tube.png\"><img decoding=\"async\" class=\"wp-image-41 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube.png\" alt=\"Two CT scan images, one above the other. The top image has four areas of the sample outlined with red rectangles. The bottom image has two areas, one of the far left and one on the far right, outlined with red rectangles.\" width=\"954\" height=\"429\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube.png 954w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube-300x135.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube-768x345.png 768w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube-65x29.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube-225x101.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.11-CT-scan-of-shelby-tube-350x157.png 350w\" sizes=\"(max-width: 954px) 100vw, 954px\" \/><\/a><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.11. CT-scan of 75 mm-diameter Shelby tube (top) and 89 mm-diameter fixed-piston (bottom) samples (Pineda et al. 2016, reproduced with permission).<\/figcaption><\/figure>\n<figure id=\"attachment_40\" aria-describedby=\"caption-attachment-40\" style=\"width: 678px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/oercollective.caul.edu.au\/app\/uploads\/sites\/143\/2025\/05\/1.12-mini-block-sampler.png\"><img decoding=\"async\" class=\"wp-image-42 size-full\" src=\"https:\/\/libraryresources.nse.org.ng\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler.png\" alt=\"The photo on the left shows a hollow cylindrical metal frame sitting on office carpet, with a shaft in the top centre. The photo on the right shows a solid cylindrical block of clay sitting on wet ground near a sampling rig.\" width=\"678\" height=\"448\" srcset=\"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler.png 678w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler-300x198.png 300w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler-65x43.png 65w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler-225x149.png 225w, https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-content\/uploads\/sites\/9\/2026\/03\/1.12-mini-block-sampler-350x231.png 350w\" sizes=\"(max-width: 678px) 100vw, 678px\" \/><\/a><figcaption id=\"caption-attachment-40\" class=\"wp-caption-text\">Figure 1.12. University of Newcastle mini-block sampler and block sample of soft silty clay (author&#8217;s own photos).<\/figcaption><\/figure>\n","protected":false},"author":1,"menu_order":4,"template":"","meta":{"pb_show_title":"","pb_short_title":"1.4 Boreholes and sampling methods","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-43","chapter","type-chapter","status-publish","hentry"],"part":24,"_links":{"self":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/43","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\/43\/revisions"}],"predecessor-version":[{"id":44,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/43\/revisions\/44"}],"part":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/parts\/24"}],"metadata":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapters\/43\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/media?parent=43"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/pressbooks\/v2\/chapter-type?post=43"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/contributor?post=43"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/fundamentalsoffoundationengineering\/wp-json\/wp\/v2\/license?post=43"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}