Expect the unexpected.\u00a0 This is\u00a0relevant when designing foundations to support a structure.\u00a0 Also,\u00a0when investigating the cause of a failure in the built environment – a forensic engineering investigation.<\/p>\n
I sometimes wonder how often the designer does this – takes the ground for granted, and gets away with it because\u00a0the foundation soils in Nova Scotia are often very strong.\u00a0 That includes well constructed, man-made filled ground.<\/p>\n
I\u00a0thought of this when an experienced structural engineering friend of mine exclaimed recently, “There’s sand everywhere in Moscow..!!”.\u00a0 He was describing his trip to the Scandinavian countries and Russia this summer.\u00a0 He went on to describe the size of the grains, the expanse of the\u00a0deposit and the level terrain.\u00a0 It was like he was seeing a\u00a0natural, undisturbed<\/em> deposit of sand for the first time.<\/p>\n That might be understandable.\u00a0 My friend has practised\u00a0structural engineering in Nova Scotia since the 1970s.\u00a0 Much of the province is\u00a0covered\u00a0by dense mixtures of gravel, sand, silt and clay – natural, undisturbed glacial soils.\u00a0 This is what my friend probably expects to find beneath\u00a0a site when he’s designing the foundations, and the steel, concrete\u00a0or timber supporting the structure above.<\/p>\n (Everything in the built environment\u00a0can be thought\u00a0to have\u00a0three major components:<\/p>\n The lower you go the less glamour there is, and too often the less attention paid to what’s below.\u00a0 “There’s no glamour in the ground”. Ref. 1)<\/p>\n Such an\u00a0expectation by my friend\u00a0would be\u00a0dangerous.\u00a0 The comfort we feel in Nova Scotia about what is below the ground surface can get you in trouble.\u00a0 It’s better to “expect the unexpected” as I learned\u00a0practising geotechnical engineering – a civil engineering specialty,\u00a0in the U.K., Australia and eastern Canada.<\/p>\n We have loose sand and silt in Nova Scotia and also soft clay – poor foundation soils.\u00a0 Not a lot but it’s out there.\u00a0 We also have\u00a0poorly constructed fills – “un-natural, disturbed<\/em>“ mixtures of different materials.\u00a0 Fill is material\u00a0brought from elsewhere and placed on\u00a0the ground to raise the level.<\/p>\n Poorly constructed fill\u00a0can cause problems for\u00a0low-rise\u00a0structures like one and two story buildings.\u00a0 In fact, when\u00a0I investigate the cause of a foundation failure, as an initial hypothesis, I “expect” to find a poorly constructed fill\u00a0beneath the foundations.\u00a0 Or one of the other poor foundation soils that occasionally\u00a0show up on our construction sites.\u00a0 This expectation\u00a0is reasonable because\u00a0I would have\u00a0evidence suggesting something is wrong down below when most of the time in Nova Scotia all’s good there.<\/p>\n Appendix<\/strong><\/p>\n Good fill in engineering usually consists of well compacted mixtures of soil – gravel, sand, silt and clay, placed on undisturbed,\u00a0natural\u00a0soil.<\/p>\n Poor\u00a0fill can consist of these materials plus\u00a0varying amounts of\u00a0topsoil, peat, roots, boulders\u00a0and\/or debris.<\/p>\n Geotechnical engineering\u00a0is\u00a0a civil engineering specialty that identifies the types of soils and rocks below the ground surface –\u00a0 below proposed foundations, measures and tests\u00a0their physical properties, and analyses and calculates how they will perform when used as\u00a0engineering materials by design engineers.<\/p>\n Reference<\/strong><\/p>\n 1. A quite well known comment by Karl Terzaghi,\u00a0considered the father of soil mechanics, the science underlying geotechnical engineering.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Expect the unexpected.\u00a0 This is\u00a0relevant when designing foundations to support a structure.\u00a0 Also,\u00a0when investigating the cause of a failure in the built environment – a forensic engineering investigation. I sometimes wonder how often the designer does this – takes the … Continue reading \n