Rock and steel samples <shown in class> The iron nail is badly rusted, while the zinc-coated nail looks brand new. The granite cobble stone is worn and rounded, but still has a lot of strength. In contrast, the old man-made concrete aggregate crumbles easily because soil conditions dissolved it. The moral of the story is that HOW we build things counts a lot. Soil conditions can greatly affect how durable and safe buildings are. For mid-term question #6: Think of modern cars – like a Hummer or Toyota Tundra. A Ford F-250 weighs about 8,000 pounds and full of technology. Faster and safer, but very expensive when damaged (easy to ‘total’ it). We don’t die as often (highway deaths are down even with increasing population, but we sure lose a lot of money because our stuff is so expensive This week’s weather <fits Chapter 9> 104 degrees F – what if today were humid also? n humid regions, 90 degrees F can be a deadly heat wave. Heat stress index adds a humidity factor to heat In winter, we add a ‘wind’ chill factor to the cold. See page 312 in the textbook Page 70 – Heat Waves Europe 2003 – 35,000 deaths due to heat, 14,500 in France Temperature Inversions Temperature Inversions Peter Sinks presents ideal conditions for deep winter weather inversions – cold air has no where to go, so it concentrates. Utah has some of the nation’s coldest winter temperatures – we are far from the ocean, far from sea level and far from the equator. Heating & Cooling Degree Days - USA White and pink areas have no summer cooling load (> 65 degrees F) Red areas > 9,000 cooling degree days What’s wrong with lots of water in the air on a hot day? - The water is hot also - Body perspiration by evaporative cooling can’t occur if the air is already full of evaporated water - Why is there no wind ‘chill’ factor with hot/humid air? <ordinarily wind brings you air that is cooler than your own body, but . . . .> Wind Chill and Heat Stress Index pages 89 and 108 Wind chill - Skin has a boundary layer of warm, humid air that is removed by wind, resulting in ‘wicking’ heat away from the body, making cold more penetrative. Today’s earthquake in China – 6.9M - 75 dead - Unreinforced buildings with mud roofs - Heavy rain preceded quake - Water adds weight and helps loosen and dissolve earthen material. This is the blocked drain at the Constitution Park retention/detention basin. They used sandbags AND a . . . . levee. I wonder why one drain is double-blocked, but with a gap – what is the value of sandbags with a gap? If a duck is settling in, is the basin for retention or detention? At Allred’s house “flash flood” conditions will be avoided by putting careful drains underneath hard surfacing so that rain water has some place to go – sink into the ground. Good drains will also help prevent damaging and slippery ice on the surface . Excavate, remove “fines” (fine material) and replace By removing clay and silt, the remaining cobblestones add strength underground and provide pore spaces for collecting rain water until it can finish draining into the soil. Even in dry Utah, flash rainstorms can cause severe surface flooding. Drains can easily get blocked by debris. Is it true that it’s not so much where you build as HOW you build? Miller campus steel-frame building, with lightweight walls and ceiling – easily shaken by a passing train, but is probably won’t fall down in a quake. Reverse the concept that modern life is turning hazards into disasters and disasters into catastrophes: instead, by making hard choices to fund better infrastructure and building practices, we turn catastrophes back into merely ‘cracks in the sidewalk.’ Some Intervention Terminology: Drain tiles, surface & underground Grading: terraces, lower angles Reduce ‘loading’ by buildings and vegetation Earth anchors and other retaining structures such as gabions, pilings, seed mats, engineering fill, bolts, spread footings. Do these play a role in Chapter 8 “Soils and Subsidence”? Creep Slump Flow Fall <once again a function of slope and water> But what about soil structure? <rock, sand, silt, clay> Lava beds in southern Idaho Geothermal heat on west side of Utah Volcanoes and cinder cones Lava beds in southern Utah old sediments (sandstone) with fossil fuels – oil, coal, gas, shale, tar sand But it is also true that we are running out of good building sites on the best ground: <page 227> Not too wet and not too steep? <yes> Has this slope changed its “angle of repose”? Depends on what is done with the steepened portions Gabions, retaining walls, earth anchors, drain pipe, surface water removal, ‘engineered fill’ material Some students conclude to be cynical – ‘We’re damned if we do and damned if we don’t.’ Is that really true? Many land formations have been “vertically deforming” for millions of years, but that does not mean we must: - add load to vulnerable soils (such as by heavy buildings); - pump out water; - pump in water; - remove minerals; - use weak foundations; - build in ‘chutes’ or flow paths; Chapter 8 Mr. Allred’s “Sets of Threes” in Soils Core, mantle and crust. Crust as bedrock, regolith, soil Soil as mineral, air/water, organic Mineral as sand, silt, clay Regolith: blanket rock, fractured, crumbling transition between bedrock and soil Regolith is being weathered – physical and chemical breakdown Soils Pyramid page 246 This set of “three” is mostly about how well soils drain, how permeable they are, how well water percolates through. In the case of clay, how stable the soil is when wet. Source unknown: probably googleimages.com and USDA, undated. Highland campus ash can Why? <freeze/thaw, salt, gravity weight> Page 243 Soil Profile or “Horizons” Point out bedrock, regolith, soil Source: EnchantedLearning.com and Googleimages.com The presence of distinct soil horizons suggests stability of the ground – it takes hundreds, even thousands of years to develop soil horizons (except in some extremely wet/hot climates) What can you conclude if excavation shows unconsolidated, unsorted materials of different types? 1. Un-layered, un-sorted soils are likely produced by recent cataclysm, like quakes, landslides, etc. 2. Strongly layered soils indicate long-term stable conditions at that location, probably less prone to soil failure. Allred excavation: 1. Humus layer 2. Root layer 3. Salt layer 4. Cobbles Hardpan or compacted soils have been ‘cemented’ by chemical action to be nearly impermeable. In contrast, permeable soils allow water to percolate through, helping prevent surface flooding or soil saturation that can cause building damage by subsidence or collapse. Alluvial fans or river deltas page 248 Implications? What about a ‘fan off-set’? <shown on the board> What is wrong with building on: - alluvial fan? - river delta? Alluvial fan with an off-set?