SIEKTETOETS. Aantal vrae: 7

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1 UNIVERSITY OF PRETORIA Department of Civil Engineering SGM210 GEOTECHNICAL PROCESSES AND MATERIALS SICK TEST UNIVERSITEIT VAN PRETORIA Departmente Siviel Ingenieurswese SGM210 GEOTEGNIESE PROSESSE EN MATERIALE SIEKTETOETS May 2011 Mei 2011 ANSWER ALL QUESTIONS CLOSED BOOK Internal examiner: Prof S W Jacobsz External examiner: Prof E Rust Marks: [56] in 60 minutes Number of questions: 7 Total number of pages: 8 BEANTWOORD ALLE VRAE TOE BOEK Interne eksaminator: Prof S W Jacobsz Eksterne eksaminator: Prof E Rust Punte: [56] in 60 minute Aantal vrae: 7 Totale aantal bladsye: 8 VAN SURNAME VOORNAME FIRST NAMES REGISTRASIENOMMER REGISTRATION NUMBER SPECIAL INSTRUCTIONS: 1. Answer all questions by writing down all intermediate steps (if applicable) and not only the final answer. 2. Non-programmable calculators are allowed. 3. Do not answer questions on opposite pages or any other place than the numbered and provided pages. TOTAL MARK: 1

2 1 Beantwoord asb die volgende algemene vrae. Please answer the following general questions. (5) (a) Benoem die grootste geologiese supergroep in Suid-Afrika. Name the largest geological Supergroup in South Africa? (1) KAROO SUPERGROUP (b) Wat is die naam van oudste behoue kontinent op aarde en waar kom dit voor? What is the name of the oldest intact continent on earth and where is it located? (2) CAPE VAAL CRATON, LOCATED OVER NORTH EASTERN SOUTH AFRICA (c) Onderstreep die jongste van die drie supergroepe hieronder? Underline the youngest of the three supergroups below? (1) Bosveld Kompleks / Bushveld Complex; Kaap Supergroep / Cape Supergroup; Supergroep / Supergroup Witwatersrand (d) Hoe oud is die Bosveldstollingskompleks as n persentasie van die ouderdom van die aarde (volgens moderne geologiese teorieë)? How old is the Bushveld Igneous Complex as a percentage of the age of the earth (according modern geological theories)? (1) 2000/4500 = 40% 2

3 2. Beantwoord asb die vrae hieronder i.v.m. radio-aktiewe datering. Please answer the questions below about radio-active dating. (6) (a) Skryf n vergelyking neer wat gebruik kan word om radio-aktiewe verval te beskryf en verklaar alle simbole. Write down an equation that can be used to describe radio-active decay and declare all symbols. (2) K = K 0 e -αt K = amount of radio active material left K 0 = amount of radio active material in beginning α = coefficient related to the rate of radio active decay t = time (b) Die halfleeftyd van koolstof 14 ( 14 C) is 5700 jaar. Hoe lank sal dit neem vir 90% van n radioaktiewe koolstof 14 monster om te verval? The half life of carbon 14 ( 14 C) is 5700 years. How long will it take for 90% of a radio-active Carbon 14 sample to decay? (4) K = K 0 e -αt 0.5 = 1 e -α.5700 α = x = 1 exp( x 10-4 t) t = years 3

4 3. Jou oom het onlangs n nuwe huis gebou. Die huis is net n paar maande oud en is laas winter gebou. Dit het in die somer baie gereen en jou oom het n paar wye krake in die mure opgemerk. Omdat jy siviele ingenieurswese studeer het hy jou dadelik geskakel met n paar vrae: Your uncle recently built a new house. The house is only a few months old and was built last winter. Lots of rain occurred during summer and your uncle noticed a few wide cracks in the walls. Because you are studying civil engineering he immediately called you with some questions: (12) (a) Jou oom het die onderstaande skets van sy huis gestuur om die krake aan te dui. Gebruik pyle op die regte posisies en dui aan die relatiewe beweging wat die huis moes ondergaan om te kraak soos getoon. Wys ook watter dele van die huis nie beweeg het nie (indien enige). Your uncle sent the sketch of his house shown below and indicated the position of the cracks. Using arrows at the correct locations, indicate the relative movement that the house must have been subjected to to crack as shown. Also indicate which parts of the house should have remained stationary (if any). (3) (b) Gegee die inligting hierbo, watter probleem grond is die mees waarskynlike oorsaak vir die krake? Verduidelik kortliks. Given the scenario described above, which problem soil is the most likely cause of the cracking? Explain briefly. (3) Heaving clays, rain caused the soil under the sides of the house to wet up and heave with respect to the centre sections of the house. (c) Wat kon die bouer tydens konstruksie gedoen het om die krake te verhoed? What could the builder have done during construction to prevent the cracks from forming? (3) Excavate clay and remove with inert material, prevent infiltration next to house by building concrete slabs of pavements, raft foundation, piled foundations (d) Wat sal jy jou oom aanbeveel om nou te doen om die probleem op te los/te verbeter? What would you advise your uncle to do now to fix/improve the problem? (3) Seal cracks with flexible crack filler, provide movement joints, stabilise moisture content under 4

5 house by constructing paving around house and take care of runoff from the roof. 4. Beantwoord asb die volgende vrae i.v.m. gletserafsettings. Please answer the questions below about glacial deposits. (3) (a) Hoe sal jy n gletser afsetting herken? How would you recognise a glacial deposit? (2) A glacial deposit contains a variety of large boulder to gravel inclusions in a matrix of fine Material. (b) In watter geologiese supergroup sal jy verwag om gletserafsettings te vind in Suid-Afrika? In which geological Supergroup can you expect to find glacial deposits in South Africa? (1) Karoo Supergroup 5

6 5. Die Karoo Supergroep: Benoem asb die vyf hoof geologiese groepe waaruit die Karoo Supergroup bestaand, beginnende by die oudste en verduidelike kortliks die omstandighede waarin elk gevorm het (een sin elk). The Karoo Supergroup: Please name the five main geological groups comprising the Karoo Supergroup, starting with the oldest one and briefly explain the conditions in which each was formed (one sentence each). (10) Dwyka group, glacial deposits Ecca group, deposited into Karoo sea from north and south gradually silting up the sea to form a lake (coal on north shores) Beaufort group, further silting up of Karoo sea with silt and sand (conditions: transition of sea to land) Stormberg group, deposited under increasingly more arid conditions (from braided streams to eventually sand desert conditions) Drakensberg Group, massive outpour of Basaltic lava 6

7 6. Langs die kus van Mosambiek kan padopvullings vir brûe oor wye river vloedvlaktes verwag word om baie te versak oor n lang tydperk. Benoem asb die probleem materiaal en gee n beskrywing van die materiaal m.b.v. die grondbeskryfwings metode van Jennings, Brink and Williams (1973) (aanvaar die materiaal is in die slegste moontlike toestand vir ingenieursontwikkelling). Along the coast of Mozambique, road embankments to the abutments of bridges over wide river flood plains can settle a lot over a long time. Please name the problem material and give a description using the soil profiling method by Jennings, Brink and Williams (1973) (assume the material to be in the worst state for engineering development). (7) Soft clay Very moist, dark brown (or grey or black), soft to very soft, horizontally bedded (or laminated), (silty) clay. Alluvium. NOTE: This clay would probably not be fissured, shattered or slickensided as it has not had a chance to dry out and crack because it was deposited in wide river valleys where water is nearly always in abundance. 7

8 7. Beantwoord asb die volgende vrae oor die onderstaande figuur. Please answer the following questions about the following figure. (12) (a) Benoem die probleem grond wat mees waarskynlik tot die landskap in die figuur aanleiding gee. Name the problem soil most likely to contribute to the landscape shown above. (1) Dispersive soils (b) Watter toetse sal jy uitvoer om die probleem grond te identifiseer? What tests will you carry out to identify this problem soil? (3) Exchangeable sodium percentage, Crumb test, pinhole test, double hydrometer test (name three) (c) Wat sal jy aan die grond doen (twee dinge) as jy dit moet gebruik vir die konstruksie van n gronddam? Verduidelik hoekom. What will you do (two things) to this soil if you have to use it for the construction of an earth dam? Explain why. (4) 8

9 Treat with gypsum to replace exchangeable sodium with calcium to make the soil less dispersive. Compact soil more that for non-dispersive material and a bit wetter than the optimum moisture content (d) Jou oom (nie die een met die gekraakte huis nie) wil n dam op sy plaas bou. Teken asb vir hom n plan (dwarssnit alleen, met afmetings) wat hy vir konstruksie kan gebruik. Hy wil die dam 4m hoog hê. Omdat die laaste oes swak was moet die dam so goedkoop as moontlik wees. Your uncle (not the one with the cracked house) wants to build a dam on his farm. Please draw a plan (cross section only, with dimensions) that he can use for construction. He wants the dam to be 4m high. Because his last harvest was poor, he wants the dam to be as cheap as possible. (4) NOTES ABOUT THE ANSWER: Rip-rap is very expensive generally not worth-while for small farm dams. A grassed layer of topsoil on the upstream and downstream slope is what most farm dams will have. An internal drainage system is also very expensive and even a toe drain as shown is a luxury in a farm dam. The sketch below is an illustration only and dimensions are typical. Reasonable variations will be accepted. 8m 3.5 5m 10m Toe drain with drainage pipe 1 2 Place topsoil and grass downstream slope 4m Place topsoil and grass upstream slope Full supply level Natural ground level Cut off key 3.5m Strip 300mm topsoil under wall Bedrock 9

Vermenigvuldig en Afdeling (Intermediêre fase)

Vermenigvuldig en Afdeling (Intermediêre fase) My Huiswerk Boek(4) Naam: Jaar: Skool: Declaration This booklet is not sold or used for profit making. It is used solely for educational purposes. You may