120729 Soil Research

7/31/2019 120729 Soil Research

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SOILFUTURE CHRISTCHURCH V2 |Dalia Al-Timimi Amanda Nakarmi Jeremy Wymer Chun Qin Zhang


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SOILFUTURE CHRISTCHURCH V2

600 - 380 Million Years ago. Sediments and Volca-noes orming.Between 370 Million Years ago and130 million years there is a lot o plate activity :pushing apart and uplit, beginning the break up.

85 Million years ago : Finally the break up o theNew Zealand Edge o Gondwana.

60 Million Years ago : The Tasman sea has ullyopended up. The New Zealand continant is wear-ring down and sinking

25 Million Years Ago : New Zealand is nearly sub-merged in the sea.

Last 20 Million Years : The uplit begins again subtly.But around 5 million years ago there was increaseduplit resulting in the ormation o the Southern Alps.

The Formation o New Zealand


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CHRISTCHURCHCITYCANTERBURY

56-34 MA 34-23 MA 23-15 MA 15-5 MA 5-2 MA 2 MA-117000

The Changing Shape o New Zealand


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Banks Peninsula was once an island. Itwas the result o two Hawaiian shield

volcanoes errupting 12 - 6 million yearsago. Shield volcanoes are nearly entire-ly made o lava ows. During the lastglaciation the mainlaind and this pen-insula were joined up as the sea wasflled with outwashed sediments. This isknown as the Cantebury Plains todayand includes Christchurch City

Banks Peninsula

Banks Peninsula

Christchurch City

Glaciers

Outwash and aggradation

The Last Glaciation sometimes reered to as the Last Ice Age occured around 100 000to 10 000 years ago. A glacier is a large mass o ice the ows downwards. They car-ry rocks and soil with them. As glaciers melt they create valleys and deposit sediments.This map shows the areas o Cantebury that have ormed because o this glaciation.

New Zealand During the Last Glaciation


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Greywacke and agrillite

Post-glacial alluvium and dune sand

Flow rhyolite, breccia and obsidian

Sandstone, siltstone and claystone

Basalt ows

Andesite

Volcanic and associated intrusive rocks Sedimentary and metamorphic rocks

The Geology o Christchurch and Surrounding Areas


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0 100 250km

Defenitions of Soil Orders found in Christchurch

Pallic Soils

Pallic Soils have pale coloured subsoils, usually light yellowish

brown or olive yellow, due to low contents of iron oxides.

The soils have weak structure and high density. Root extension is

limited and the drainage of water through the soils is slow.

Pallic Soils occur predominantly in the eastern parts of North andSouth Islands and the Manawatu; in places that are dry in

summer and moist in winter. In many areas the surface horizons

are waterlogged in winter due to the slow drainage. The

precipitation is usually between 500 and 1000 mm per year.

They occur in parent materials which a re not strongly altered by

weathering. The soils are only weakly leached with moderate to

high levels of calcium and other cations

Gley Soils

Gley Soils are soils that have been strongly affected by waterlog-

ging and have been reduced to depth.

They have light grey subsoils usually with reddish brown or brown

mottles. The grey colours extend to more that 90cm depth.

Waterlogging occurs in winter and spring and some soils remain

wet throughout the year.

They often occur in low parts of the landscape where there are

high ground water tables

Brown Soils

Brown Soils have a brown or yellow-brown subsoil below a dark

grey-brown topsoil. The brown colour is due to thin coatings of

iron oxides which have weathered from the parent material.

The majority of Brown Soils occur in places in which summer

dryness is uncommon and which are not waterlogged in winter.

The precipitation is usually more that 1000 mm per year although

it may be less in some stony soils.

They occur in loess, alluvium or slope debris parent materials

which are little altered by weathering. The soils are however

usually strongly leached and are acid with low levels of calcium

and other basic cations. They are the most extensive New

Zealand soils, particularly in the South Island mountainsPodzol

Soil Types

Melanic

Organic

Recent

Brown

RawPallic

Giley

Ultic

Brown-story

Pumice

Granular Allophanic Oxidic

Geographic Distribution o the Dominant Soil Types in New Zealand


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Urban Areas of Christchurch

1:500,000

0 5 km 1 0k m 1 5k m

04.CBD

Weathering

UWSWMWHCCWRW

UnweatheredSlightly WeatheredModerately WeatheredHighly WeatheredCompletely/Extr. WeatheredResidual Soil

Source Key

Undrained Shear Strength

VSSFStVStHFb

Very softSoftFirmStiffVery StiffHardFriable

Cu (kPa)200

Relative Density

VLLMDDVD

Very looselooseMedium DenseDenseVery Dense

01.Kairaki BeachBorehole Location

DataSoil Prole

SPT/Particle SizeSoil Description

Colour

- 1.5 W VL

- 2.3 W VS

- 3.0 W MD

- 5.1 W L

- 6.1 W L

- 7.5 W MD

- 15.0 W MD

02.Wainoni

DataSoil Prole


Colour

- 1.3 M VS

- 1.9 W VL

- 3.0 W VS

- 8.0 W L

- 13.5 W D

- 15.0 W VSt

03.Hallswell

DataSoil Prole


Colour

- 0.8 W S

- 1.5 W D

- 6.0 W MD

- 7.0 W F

- 7.5 W VS

- 10.5 W F

- 22.0

DataSoil Prole


Colour

- 0.8 W VL

- 1.5 MW VL

- 5.5 W L

- 7.0 W L

- 10.5 MW L

- 10.5 W VL

- 19.0

- 14.5 W VL

Characteristics Soil Profles


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04.Avondale

DataSoil Prole


Colour

- 0.8 D L

- 2.8 M-W F- 3.0 W L

- 3.5 M S

- 4.7 W L

- 7.5 W L

- 8.0 W L- 8.2 W L

- 9.0 W D

- 9.8 W D

- 10.5 W D

- 11.7 W MD

- 15.0

06.Bexley

DataSoil Prole


Colour

- 0.8 D

- 2.2 M VS

- 4.5 MD

- 6.0 W MD

- 15.0

08.Richmond

DataSoil Prole


Colour

- 1.0

- 3.5 W VS

- 4.0 W MD

- 6.0 W MD

- 17.0 W VD

- 19.0 W VD

07.Burwood

DataSoil Prole


Colour

- 0.8

- 1.5 M

- 2.9 W VS

- 4.5 W MD

- 6.0 W MD

- 10.5 W MD

- 11.2 SW MD

- 15.0 W D

- 0.35 D L

- 3.1 W L

- 4.8 W MD

Colour

09.Spencerville

DataSoil Prole


- 5.2 W MD- 5.4 W MD

- 5.0 W MD

- 5.6 W MD

- 5.8 W MD

- 7.5 W D

- 10.7 W MD

- 11.4 W MD

- 11.6 S MD

- 13.0 W MD

- 14.8 W MD

- 15.3 W MD

- 17.3 W D

- 19.3 W D

DataSoil Prole


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2 cm

Gravel and Gravelly Soils

Clean Gravels

Gravels with nes

Well graded gravels or gravel - sand mixtures,little or no ne

Pedon Scale Core Section Aggregate Scale Micropore scale

Silty gravels, gravel-sand-silt mixtures A loose granular substance carried byrunning water

A loose granular substance

loose granular substance, slightlyweathered

loose granular substance, highlyweathered

Material characteristic of boggy, acidground consisting of partlydecomposed vegetable matter.

Very low porosity -angular grains, many sizes(poor sorting)

High porosity -rounded grains, many sizes(poor sorting)

High porosity -rounded grains, many sizes(poor sorting)

High porosity -

rounded grains, uniform size (goodsorting)

High porosity -rounded and angular grains, manysizes(good sorting)

High porosity -angular and rounded grains, manysizes

(poor sorting)

Strong thin platey structure

Sand and Sandy Soils

Clean Sands

Sands with nes

Well graded sands or gravelly sands, little or nones

Silty sands, sand-silt mixtures

Silt Soils

Peat Soils

Fine sand carried by running water anddeposited as a sediment.

A soil like material consisting of partlydecomposed vegetable matter

WHITE COLOUR ASSIGNED TO PORE AND BLACK TO SOIL

Soil Types, Structure and Porosity


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The main soil types o Christchurch consist o granular substancessuch as sands, gravels, non-plastic soils and their mixtures. Thesegranular soils are the main reason or liqueaction. These soils derivetheir stiness and strength through grain to grain contact stresses.Shallow soils have small grain to grain contact stresses, so they arerelatively sot and weak. Soils at great depth have large grain to

grain contact stresses so they are relatively sti and strong.

The soil types evident in the borehole samples are loose. Loose soilshave more voids in their inherent structure (since they were not wellcompacted when deposited) Hence, when shaken, they show largetendency or densifcation (contraction) which in turn leads to rapidpore water pressure build up and eventual liqueaction in only ewcycles o strong shaking. Since these soils are loosely packed andare highly deormable (compressible), liqueaction will be severelymaniested and will result in very large ground movements and nearlycomplete loss o load carrying capacity. This is why loose soils areparticularly prone to liqueaction and show very severe consequenc-es o liqueaction. Very Dense soils are rare in the borehole samples.Very dense soils will allow or limited tendency or densifcation andhence produce low excess pore water pressures and thereore would

have a much higher liqueaction resistance. Clays are not evidentin Christchurch soils. Clayey soils in general, derive stiness andstrength rom an additional mechanism (cohesion) and hence areconsidered non-liquefable.

Characteristics o Christchurch Soil


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DENSE SEDIMENT

SATURATED LOOSE SEDIMENT

The young sediment christchurch is built on means the city is prone to the effects ofliquefaction during an earthquake event. The city has been noted by international expertsas the most prone to liquefaction in the world. Liquefaction variation is determined by theepicentre location, magnitude, depth, duration and geological conditions.Flat areas such as this, where the water table sits only a few meters under the surface,release a build up of pressure through sand boils and waterspouts in many areas andin lateral spreading and cracking near rivers. This occurs as waters are removed from

the lower lying saturated loose sediment underground during the shaking. The wateris forced up through weak points in the denser sediment just below the surface. As thisoccurs the loss of water in the lower layers gives way to compaction, producing a varietyof effects to the natural and built environment.


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DENSE SEDIMENT

COMPACTED SEDIMENT

SETTLED FOUNDATIONSWeakened soil can cause buildingsto sink or tilt as compaction occures.this results in deormation or crackingo the building.

SUBSIDED LANDAs the lower sediment compacts andmoisture is orced upwards, largechunks o land subside, damagingbuildings above and leaving largesteps in the landscape.

FLOATED SERVICESAs the pressure increasespipes become buoyant andoat up through the ground.manholes are pushed upout o the roads and pipesbecome damaged andsevered in places, leakingtheir contents into the earth.

SAND BOILSStrong surace evidence thatliqueaction has occured. thepressure in the ground orces theliquifed silt upwards and out o theground covering the surace in mudand water.

WEAKENED SOILTrees, power poles, lampposts and similar objectsare unable to be supportedproperly by the liquifedground.

LATERAL SPREADINGEarth on river banks slide towardseach other under the pressurecausing signifcant cracks to openup. this may extend quite somedistance back rom the river itsel.


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The map indicates areas of Liquefaction ground damagepotential dened for Christchurch.

High Liquefaction PotentialAreas in Christchurch rated High Liquefaction potential maybe affected by lateral spreading and signicance groundsubsidence that is likely to be greater than 300mm.

Moderate Liquefaction PotentialAreas in Christchurch rated High Liquefaction potential maybe affected by 100-300mm of ground subsidence.

Low Liquefaction PotentialAreas in Christchurch rated Low Liquefaction Potential maybe affected up to 100mm of g round subsidence.

High Liquefaction potential may be expectedAreas in Christchurch rated High Liquefaction potential maybe expected are very likely to be affected by Liquefaction,with the data that was provided at this stage it is difcult to

determine the accurate information.

Low Liquefaction potential may be expectedAreas in Christchurch rated Low Liquefaction potential may beexpected are very unlikely to be affected by Liquefaction, withthe data that was provided at this stage it is difcult todetermine the accurate information.

No Liquefaction not predictedAreas in Christchurch rated No Liquefaction not predictedare areas that unlikely for Liquefaction to occur

PortHills

Parklands

Brooklands

Belfast

SH1

PapanuiAirport

SH1

SH1 Hornby

SH73

Avon-

Heathcote

Estuary

Ferrymead

LinwoodRiccarton

Wainoni

WaimakaririRive

r

Waim

akaririRiv

er

High Liquefaction potential

Moderate Liquefaction potential

Low Liquefaction potential

High Liquefaction potential may be expected

Low Liquefaction potential may be expected

No Liquefaction / not predicted

Major Roads

Rivers

Christchurch City Boundary

Port Hills - No Liquefaction expected

N

8km6420

Scale: 1:100,000


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Areas where the Water table is at its highest is very like;y for Liquefaction ground damage tooccur during an Earthquake, other areas with a Lower water table is unlikely for Liquefactionground damage to occur.

013 245678910111213141516

-40

-30

-20

-10

0

10

20

30

Elevation(m)

RussleyRoad

WaimainRoad

RollestonAvenue

FitzgeraldAvenue

BexeyRoad

Distance from Pegasus Bay (km)

Sea Level Water-table

Ground Surface

Top of Gravel

4km3210

Scale: 1:100,000

RussleyRoad

WaimainRoad

RollestonAvenue

FitzgeraldAvenue

BexeyRoad

East - West Cross Section through Christchurch

40m

CBD


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120729 Soil Research