{"id":883,"date":"2013-01-11T13:40:34","date_gmt":"2013-01-11T13:40:34","guid":{"rendered":"http:\/\/www.ericjorden.com\/blog\/?p=883"},"modified":"2013-01-11T13:40:34","modified_gmt":"2013-01-11T13:40:34","slug":"my-first-forensic-engineering-investigation","status":"publish","type":"post","link":"http:\/\/www.ericjorden.com\/blog\/2013\/01\/11\/my-first-forensic-engineering-investigation\/","title":{"rendered":"My first &#8220;forensic engineering&#8221; investigation"},"content":{"rendered":"<p>(The following is one in a series of cases I\u00a0have\u00a0investigated\u00a0that illustrate\u00a0the different types of\u00a0<strong>structural failures<\/strong> and accidents that occur <strong>resulting in civil litigation<\/strong>, and the forensic engineering methods I used to investigate the cause)<\/p>\n<p>The investigation is reported under the following\u00a0main headings with several sub-headings:<\/p>\n<ul>\n<li>The case (a description of the failed structure &#8211; significant cracks in a building, the &#8220;lega&#8221;\/technical issues, and my &#8220;client&#8221;<\/li>\n<li>&#8220;Forensic engineering&#8221; investigation of the failure and the methods used<\/li>\n<li>Cause (of the failure)<\/li>\n<li>Post mortem (<strong>an interesting side story and a lesson learned<\/strong>)<\/li>\n<\/ul>\n<h1 align=\"left\"><strong>The case<\/strong><\/h1>\n<p>I carried out my first &#8220;forensic engineering&#8221;\u00a0investigation\u00a0during my 5th year studying civil engineering at\u00a0the University of\u00a0New Brunswick (UNB).\u00a0 This was at a time when I was an engineering student and\u00a0had no understanding\u00a0at all of forensic engineering, and wasn&#8217;t even qualified as a professional engineer.<\/p>\n<p>Nevertheless, this was a significant and costly building failure but, fortunately, not a catastropic one.<\/p>\n<p>We took our lectures in a room on the second floor of a two and a half story brick clad building with a full basement &#8211; the &#8220;engineering building&#8221; on the\u00a0UNB campus.<\/p>\n<p>During our 5th year the foundations of one wall of the building settled causing 1&#8243; to 2&#8243; wide, vertical\u00a0cracks &#8211; as I remember the size, to appear in the front, left corner of a wall of the lecture room.\u00a0 You could see daylight through the cracks.\u00a0 This would be significant damage to an existing building<\/p>\n<p><strong>&#8220;Legal&#8221;\/Technical\u00a0issue<\/strong><\/p>\n<p>To me as a student with an interest in\u00a0geotechnical and foundation engineering, the cause of the cracks was an issue of considerable interest.\u00a0 I\u00a0undertook to investigate and report on the cause\u00a0to meet the\u00a0requirements of one of\u00a0my courses.<\/p>\n<p><strong>Client<\/strong><\/p>\n<p>My &#8220;client&#8221; in a sense was the professor who was giving the foundation engineering course.<\/p>\n<h1>&#8220;Forensic engineering&#8221;\u00a0investigation<\/h1>\n<p>My\u00a0&#8220;forensic engineering&#8221; investigation involved the following:<\/p>\n<ul>\n<li>Visually assess the exterior of the engineering building<\/li>\n<li>Determine how the building was constructed<\/li>\n<li>Research construction techniques<\/li>\n<\/ul>\n<p><strong>Visual assessment<\/strong><\/p>\n<p>A visual assessment of the exterior of the building found that an addition to the engineering building was being\u00a0constructed immediately adjacent the existing building.\u00a0 Consulting engineers for\u00a0UNB had hired a contractor to build a new engineering building adjacent\u00a0the old &#8211; only a few feet away.\u00a0 Construction\u00a0involved a deep excavation adjacent the shallow foundations of the\u00a0existing building.<\/p>\n<p><strong>Building construction\/Construction technique<\/strong><\/p>\n<p>I\u00a0learned that the existing engineering building was supported on shallow spread footings founded in the natural soils.\u00a0 Excavating near and well below\u00a0natural foundation soils like these requires their support in some manner to prevent undermining the soils.<\/p>\n<p>I saw during my visual examination that the contractor had installed a\u00a0soldier pile shoring system to temporarily support the foundation soils\u00a0beneath the\u00a0existing building.<\/p>\n<p>This type of foundation support system consists of steel piles driven vertically into the ground at regular intervals adjacent the existing building foundations.\u00a0 The piles may also be installed in\u00a0previously bored\u00a0holes in the ground eliminating the ground vibration from pile driving.\u00a0 As the excavation\u00a0is taken\u00a0deeper\u00a0timber &#8211;\u00a0lagging,\u00a0is inserted horizontally between the piles to support or shore up the\u00a0soil in the side of the excavation\u00a0&#8211; in this case soil that is adjacent the existing building&#8217;s foundation soil.<\/p>\n<p>A soldier pile shoring system is a good support system if constructed properly and its limitations kept in mind.<\/p>\n<p><strong>Research construction technique<\/strong><\/p>\n<p>I researched the shoring system and found that it &#8220;gives&#8221; or yields a little &#8211; deflects along it&#8217;s length in engineering terms, when mobilizing its strength to provide support to the soil it is retaining.\u00a0 The retained, shored up soil\u00a0behind the shoring system gives a little as well\u00a0&#8211;\u00a0moves sideways and away from the foundation soils to which it is providing lateral support.\u00a0 This effectively undermines the foundation soils a little causing the soils\u00a0to settle and the building foundations to settle as well.<\/p>\n<p>This deflection\u00a0is due to the piles bending along their length.\u00a0 The piles will also deflect\u00a0or tilt a little if they are not\u00a0driven or embedded deep enough during installation.<\/p>\n<p>This lateral movement of the shoring system and settlement of the soils and foundations is normal.\u00a0 It\u00a0can be\u00a0negligible if the shoring system is properly designed and installed.\u00a0 The movement can be significant causing damage to the foundations\u00a0the shoring system\u00a0is designed to protect if\u00a0the support system\u00a0is not well designed and installed.<\/p>\n<p>Installing soldier piles by driving them in place causes the soils in the immediate area to vibrate.\u00a0 Soil settles when it is vibrated.\u00a0 Anything in the soil &#8211; like building foundations, settles as well.<\/p>\n<h1>Cause<\/h1>\n<p>I analysed the data that I had collected &#8211; the manner of construction of the\u00a0shoring system and the\u00a0results of my research, and\u00a0concluded\u00a0the cause of the failure and submitted my student engineering report.<\/p>\n<p>In this case the soldier pile\u00a0system deflected too much causing the foundation soils to yield or move\u00a0sideways and settle in the process.\u00a0 This caused the building walls to settle as\u00a0well and the corners to crack and open up.\u00a0 The deflection was probably due to a combination of the causes noted above:<\/p>\n<ul>\n<li>Vibration of the soils during installation of the piles<\/li>\n<li>Tilting of the soldier piles due to\u00a0shallow embedment<\/li>\n<li>Deflection along the length of the\u00a0piles<\/li>\n<\/ul>\n<h1><strong>Post mortem<\/strong><\/h1>\n<p>I passed my year so I must\u00a0have got it right, not treading on any toes in the process \u2013 the engineers who\u00a0approved the soldier pile system that failed were my professors who had formed\u00a0a consulting engineering company to do this type of work.\u00a0 Failures occur in spite of the best efforts\u00a0of the best people.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>(The following is one in a series of cases I\u00a0have\u00a0investigated\u00a0that illustrate\u00a0the different types of\u00a0structural failures and accidents that occur resulting in civil litigation, and the forensic engineering methods I used to investigate the cause) The investigation is reported under the &hellip; <a href=\"http:\/\/www.ericjorden.com\/blog\/2013\/01\/11\/my-first-forensic-engineering-investigation\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/posts\/883"}],"collection":[{"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/comments?post=883"}],"version-history":[{"count":25,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/posts\/883\/revisions"}],"predecessor-version":[{"id":1022,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/posts\/883\/revisions\/1022"}],"wp:attachment":[{"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/media?parent=883"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/categories?post=883"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.ericjorden.com\/blog\/wp-json\/wp\/v2\/tags?post=883"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}