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Chapter 5 Soluble rocks Solubility – threatens water storage and water conveyance projects with sever problems involving potential leakage and ground collapse.

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Presentation on theme: "Chapter 5 Soluble rocks Solubility – threatens water storage and water conveyance projects with sever problems involving potential leakage and ground collapse."— Presentation transcript:

1 Chapter 5 Soluble rocks Solubility – threatens water storage and water conveyance projects with sever problems involving potential leakage and ground collapse

2 Question: What is the most common soluble rock type?

3 Question: What are the 3 groups or classes of limestone? The divisions are based on their mode of formation? –Biochemical –Chemical –Detrital

4 Biochemical limestone Rocks formed from living organisms – shells of microscopic planktonic foraminifera and plates of calcareous algae Calcareous algae Upper Tertiary Dhofar, Southern Oman


6 Ammonite and tubiphythes in "Treuchtlingen Marble"; trade name: Jura Gelb Upper Jurassic (Malm Delta) Treuchtlingen, Germany

7 Oolith Lower Aptian Near Doman, Recita Zone, Southern Carpaten, Rumania

8 Belemnite and tubiphythes "Treuchtlingen Marble" Upper Jurassic (Malm Delta) Treuchtlingen, Germany

9 Sponge Devonian ? Bucchan Caves?, Australia

10 Belemnite battlefield Lower? Jurassic Mistelgau, Northern Bavaria, Germany

11 fossiliferous limestone, very rich in crinoids; trade name: Derbyshire Fossil Carboniferous Coahill, Derbyshire, England, Great Britain

12 Beige limestone with rounded intraclasts and fossils (gastropods, corals)

13 Red limestone with bivalve shells and other molluscs, brachiopods? Helvetikum Grünten, Allgäu, Germany

14 Recrystallized stromatopore-reef limestone (Lahn-Marble) with stromatopores, crinoids und tabulate corals (Thamnopora or Heliolites); grey ruditic lime is normal background sedimentation; red is storm sediment Middle Devonian Bongard-Quarry (?), Villmar, Kreis Limburg-Weilburg, Germany

15 Reddish coral limestone Carboniferous Avon Gorge, Bristol, UK

16 Brown-reddish coral limestone ?, probably Carboniferous or Devonian Beach fortification near the bunkers from WWII, Dunkerque, France

17 Biochemical limestone Bedded and jointed Hardness 3 to 4, mineral calcite and dolomite Chert horizons hardness 6 - silica

18 Chert concretion from Boom Clay Belgium

19 Chert cherts are formed from the tiny (0.5 to 1.5 mm) silica shells of radiolaria.

20 Chalk one unusual example of biochemical limestone is chalk – compacted but not lithified

21 Chalk white friable and very porous shells of microscopic planktonic foraminifera and calcareous algae

22 Chalk massive uniform layers or very thick beds separated by shale partings not typical to be jointed as is most limestone Horizons of chert concretions common

23 Chalk

24 Other names dependent upon content of clay and chalk Chalk > 95% CaCO3 Clay Chalk >5%<13% clay Clay Marl>13%<25% clay Calcareous mudstone >25%clay

25 Chemical limestone Precipitate of calcite CaCO3 (uncommon), occurs in warm CaCO3 rich seas oolites.

26 Oolites Concentric radial structure

27 1. Precipitation of CaCo3 sea water is almost saturated in CaCO2 – decrease in the content of CO2 by warming or by the action of plants in shallow water can cause calcium carbonate to precipitate

28 2. Precipitation of CaCo3 rivers saturated in CaCO2 precipitate it when they enter saline environments, called travertine

29 3. Precipitation of CaCo3 groundwater saturated in CaCO3 precipitates it when the groundwater emerges into the atmosphere, springs called tufa brick in a church

30 4. Precipitation of CaCo3 evaporation in arid and semiarid regions leads to the precipitation of CaCO3 called caliche

31 Detrital limestone particles of CaCO3 cemented together, very porous Names are dependent upon the size and nature of the particles – clay – calcilutite – sand – calcarenite – gravel – calcirudite –shell fragments – coquina or shell-hash limestone

32 calclutite

33 calcarenite sand size grains of CaCO3

34 calcirudite

35 Question: Compare the strength of calcarenite with orthoquartzite with respect to their particles, and cement. What is the expected difference in porosity?

36 Dolostone or Dolomite recrystallized limestone which contains Mg composed 90% of the mineral dolomite, less soluble than calcite composition changes after deposition – type of chemical re crystallization

37 Dolostone or Dolomite dolomitization is not always uniform

38 Dolostone or Dolomite Fractures in the dolostone bedrock conduct groundwater

39 Dolostone or Dolomite Mountain range called dolomites

40 Marble What type of rock is it? Marble – metamorphic rock formed from limestone – complete recrystallization

41 Evaporate rocks Gypsum CaSO4 2H2O Anhydrite CaSO4 Halite NaCl

42 Evaporate rocks Gypsum CaSO4 2H2O Anhydrite CaSO4 Halite NaCl

43 Evaporate rocks Gypsum CaSO4 2H2O Anhydrite CaSO4 Halite NaCl

44 Gypsum massive or bedded associated with rock salt, shale, dolomite and limestone bituminous material common often intensely folded and brecciated – due to its formation: Anhydrite + hydration results in Gypsum and EXPANSION and deformation highly soluble – 170 times more soluble than calcite but only 1% that of NaCl lacks strength for caverns to form

45 Anhydrite stable form of CaSO4 above 43 degrees stable at any temperature when there is no H2O present Hydration – volume expansion of 35% Hydration depth is less than 150 m (fig 5.9) Hydration changes the anhydrite to Gypsum 3.5 Mpa pressure due to hydration

46 Halite or Rock Salt massive beds with inclusions of brine salt dome formation – diapirs Fig. 5.8 – intrusions of salt into overlying rocks salt domes – up to 3 km diameter steep and vertical joints impermeable – trap for oil cap rock deformed source as much as 5 km deep salt diapirs that pierce the ground become salt glaciers

47 salt dome

48 Salt glacier

49 Solution processes and effects Common in limestone, dolostone and marble

50 Stages of Karstification Youth Maturity Old age

51 Stages of Karstification Youth Maturity Old age

52 Two kinds of subsidence dissolved –slow subsidence sinkholes –densification of sediments collapsed – p166 fig 5.17, 5.16 –loss of support triggered by: lowered groundwater level heavy rain storms – wash out of sediments vibrations increased infiltration

53 Two kinds of subsidence dissolved –slow subsidence sinkholes –densification of sediments collapsed – p166 fig 5.17, 5.16 –loss of support triggered by: lowered groundwater level heavy rain storms – wash out of sediments vibrations increased infiltration

54 Geologic Controls on the Formation of Karst Cavities occur in almost all soluble rocks – but their size and shape is dependent upon the composition, texture, and structure of the rock, its strength and its geological history

55 Residual Soils limstone gives terra rosa a soil red due to the high content of hematite and limonite, FeO; clay rich and fissured thus well drained

56 Residual Soils dolominte gives a soil called wad rich in magnesium rich minerals such as clorite and montmorillonite are highly compressible and swelling Natural water content of more than 200% (greater than bentonite)

57 Volcanic tuff - montmorillonite

58 Engineering properties Case study Vajont slide in Italy

59 Engineering properties

60 Exploration targets and problems subsurface cavities and sinkhole areas – location determination of the surface of the solid rock below the residual soil, top of rock (SAME for Sweden) location of highly soluble layers gypsum – drilling to determine occurrence anhydrate – gypsum contact

61 Water supply water plentiful but the system is very sensitive to pollution water will result in CaCO3 deposits on pipes

62 Rock salt impermeable – proposed site for deposit of burnt atomic fuel

63 Foundation karsts – each bearing point must be studied cavities – collapse potential must be studied – drill plan dependent upon the risk pinnacle rock top § differential settling § differential support § pinnacles undermined § piles - glide off pinnacle

64 Foundation gypsum and water leads to settling, collapse and solution anydydrate leads to heaving calcarenite and chalk have limited bearing capacity weathered products extremely compressable

65 Dams and Reservoirs All the same problems as mentioned for Foundations above

66 Dams and Reservoirs IMPOUNDMENT of WATER not obvious no lake may form if water flows through the ground dissolve new channels washout of old channels dissolution of gypsum and salt foundation stability endangered by clay seams high pore pressures can occur if the foundation is located on an upwardly discharging spring

67 Tunneling limestone –relatively strong – caverns with considerable size can form naturally in them –karsts – are a problem – collapse and sudden inflow of water

68 Tunneling evaporate rocks –salt · massive - good, bedded – poor · easily dissolved · organic materials common – risk for explosions · oils and gas outbursts –gypsum · fractured · disturbed bedding and voids · squeeze common · dissolvable

69 Tunneling chalk, calcarentites, and cacirudites –weak – requires additional supports due to collapse risk –>15 Mpa >300 m plastic ductile deformation –<300 m elastic brittle deformation

70 Materials of construction Aggregates: limestone and dolomite – good in both asphalt and concrete given a reasonable strength they give good particle shape good particle size distribution NOTE – strength in asphalt is not sufficient for cold climates where studded tires are used >15% argillite not good

71 Materials of construction Aggregates: chert – reactive in concrete and fractures in extreme cold gypsum is a SO4 – not allowed in concrete!! too weak for asphalt

72 Materials of construction Dimention stone limestone, dolomite and marble are all very common – not always good on exteriors (warping)

73 Case Study Failures and Near Misses from surface Collapse over Cavities Sinkholes associated with lowered ground water table

74 West Driefontein mine – south African mine increased rate of ground-water with drawl caused the main surface stream to go dry cavern had developed 117m deep boring in residual soils grouted in 171 holes, 9-15 m deep surface paved to prevent infiltration around the plant 60 m in all directions the entire crushing plant disappeared into a sinkhole – with 29 people – never found the hole was 55 m in diameter and more than 30 m deep

75 South Africa train 1975 – near the Driefontein mine ground water lowered in the Dolomite railroad was closed for passenger trains over a year during which remedial measurements were taken 8 days after the rout was re opened a sinkhole formed the train driver could not stop the train in time 3 coached derailed – 2 left hanging over the sinkhole

76 Failure of the Tarpon Strings Bridge – Florida 1969 – 3 foundation units were swallowed into a sinkhole the railroad traffic did not stop in time – one person was killed

77 Palermo airport, Sicily cavity of 12,000 m3 volume 2 m below the pavement cavity extended over the entire width of the runway just at the place where aircraft touch down cavity was plugged with concrete through holes drilled from the pavement

78 Kentucky Dam 10 potential sites studied bedrock was flat lying limestone – overlain by 30m of tertiary sediments – overlain by cherty residual soil karsts in the limestone weathered down 95 m (Fig. 5.23) solution more intense at changes in bedding orientation due to the higher frequency of joints

79 Kentucky Dam both dam abutments were situated on thick sequences of soils and alluvium bedrock had numerous caves 65 m deep and 18 m wide most partially filled with residual clay solution cavities were very continuous laterally along certain beds with unstable minerals

80 Kentucky Dam solved drillings were made so miners could go down and clean the cavities of clay and soil the cavities were filled with grout material this formed an underground cutoff 50 km of diamond core holes 2.3 km of calyx holes 20,000 m3 grout

81 Great falls dam horseshoe formed river leakage through the divide of 10 % the capacity leakage increase by 1% per year the lake level was lowered and 96 inlets were detected trace elements were used to trace the flow these were then grouted and leakage cut off

82 UCSC Karstic limestone where an Olympic size swimming pool was to be constructed Relocated to miss karts filled with silt – Since this is an earthquake area, near the San Andreas Fault Zone, liquefaction would be probable over silt new location in a collapsed dolline the base was filled, lined and under the liner a collector for leakage water installed

83 Grout Curtain at El Cajon Dam thin arch dam 238 m high to be built in karstic area overlain with volcanics and 4 major faults in the area drillings revealed caves 200 m lateral extent grout curtain made in form of a bathtub 514 km of drillings 14 km galleries grout curtain area m2 2 ½ years to complete 10,000 m3 cave detected during exploration resulted in the relocation of the bathtub grout curtain

84 New Mexico Mc Millan reservoir 1893 gypsum beneath the reservoir abutment soon after filling the cliff began to crack and collapse 1909 embankment built parallel with the cliff to cut off the contact with the water 12 m subsidence 1942 underground caves and chanels 60 million m3

85 Oklahoma 1965 – 11 m high dam soon after construction a sinkhole formed volume of m3 under the spillway

86 Pollution in karst – Australia – Mount Gambier, town with inhabitants located on limestone The karstic limestone aquifer overlies a clay bed which is impermeable (aquiclude) which in turn overlays a delta mollase aquiclude The upper aquifer is polluted with waste from industry and sewage The lower aquifer is the source of ground water

87 Pollution in karst – Australia – Mount Gambier, the state of leakage between the two aquifers is threatened if the amount of ground water pumped out of the lower aquifer exceeds the infiltration there is a risk that the direction of leakage through the aquiclude will change so leakage will be from the upper polluted aquifer down to the confined aquifer today the lower aquifer is artesian and under high pressure but if the pressure gradient is lowered this will change

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