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Images for liquefaction silt; more images...

Images, UC QuakeStudies

The ruins of the historic Durham Street Methodist Church in the aftermath of the 22 February 2011 earthquake. The only parts of the building still upright are those supported by steel braces placed there after the 4 September 2010 earthquake to strengthen the building as it awaited repairs. Rubble has spilled out onto the street, knocking over the safety fences that were also erected after September. Silt from liquefaction has covered the road around the church.

Images, UC QuakeStudies

The ruins of the historic Durham Street Methodist Church in the aftermath of the 22 February 2011 earthquake. The only parts of the building still upright are those supported by steel braces placed there after the 4 September 2010 earthquake to strengthen the building as it awaited repairs. Rubble has spilled out onto the street, knocking over the safety fences that were also erected after September. Silt from liquefaction has covered the road around the church.

Images, UC QuakeStudies

Workers operate a drilling rig, sampling soil as part of EQC's geotechnical investigation of TC3 land. The photographer comments, "The work of getting 'soil' samples from all the areas marked as green/blue zones in Christchurch. These areas may be susceptible to liquefaction if a major earthquake occurs. The soil samples were a failure as all they found was sand".

Images, UC QuakeStudies

Warped bike stands and liquefaction silt on the corner of High, Colombo and Hereford streets. A public walkway down Colombo Street to a small viewing area in the Square was opened up for a few weekends to allow the public to see inside the Red Zone.

Images, UC QuakeStudies

An abandoned residential property at 32 Waygreen Avenue in New Brighton. The front of the section is overgrown with weeds and silt from liquefaction. One brick fence posts remain upright and two others have toppled onto the grass. The gutter has partly flooded.

Images, UC QuakeStudies

An abandoned residential property at 12 Seabreeze Close in Bexley. A damaged window has been boarded up around the side of the house and the front window has been vandalised with graffiti. The yard is covered with weeds and silt from liquefaction.

Images, UC QuakeStudies

Trees alongside the Avon River in Richmond. The river level is high, and the water is grey with silt. One of the trees is leaning towards the river. The photographer comments, "High river levels because of liquefaction in the Avon. Near 373 River Rd, Richmond".

Images, UC QuakeStudies

An abandoned residential property at 28 Waygreen Avenue in New Brighton. The front of the section is covered with weeds and silt from liquefaction. Three broken chairs lie outside the front of the house. The front door is open. 'HM' has been spray-painted in green onto the front wall.

Images, UC QuakeStudies

Damage to Medway Street in Richmond. The road surface is cracked and buckled, and covered in liquefaction silt. A temporary road sign restricting speed to 30 is visible, with road cones behind. The photographer comments, "Medway St, between Woodchester Ave and River Rd. Woodchester Ave on right just beyond the 30 sign".

Images, UC QuakeStudies

Damage to the garden of a house in Richmond. Liquefaction is visible among the plants and on the driveway. The photographer comments, "These photos show our old house in River Rd and recovery work around Richmond and St Albans. Back lawn under 10cm of water and silt".

Images, Alexander Turnbull Library

In a Christchurch street still covered in liquefaction man weeps over his four-wheel drive car, which has a number plate showing the word 'macho'. Two women who are working at clearing the road of silt watch and one of them observes that 'he's not handling the quake well at all... Keeps getting silt smears on the 4 x 4!' Context - The Christchurch earthquake of 22 February 2011. Liquefaction is a particular problem. There is a point being made here about the 'macho' man who sobs over his car and the two staunch women who get on with the cleaning-up effort. Quantity: 1 digital cartoon(s).

Images, UC QuakeStudies

An abandoned residential property at 4 Waireka Lane in Bexley. The driveway is covered with weeds and silt from liquefaction. One of the garage doors is twisted and the other has 'HM' spray-painted on it. The number four has been spray-painted on the brick wall under the window.

Images, UC QuakeStudies

Water and liquefaction flows into the Avon River in Richmond. The water level is very high, and the water is cloudy with silt. The photographer comments, "Water from Dudley Creek took a shortcut across the road into the Avon. It doesn't have much of a drop from the road to the river".

Images, UC QuakeStudies

Liquefaction in a residential property in North New Brighton. The fence has subsided into the silt, and a temporary water line runs along the street in front. The photographer comments, "Because this is in the Christchurch red zone the people living here, if they have lost one of the normal essentials such as sewage they will not get it repaired. It is get out or live in third world conditions. The blue line is the temporary water pipe, which will be removed when the area is depopulated".

Research papers, University of Canterbury Library

As a consequence of the 2010 – 2011 Canterbury earthquake sequence, Christchurch experienced widespread liquefaction, vertical settlement and lateral spreading. These geological processes caused extensive damage to both housing and infrastructure, and increased the need for geotechnical investigation substantially. Cone Penetration Testing (CPT) has become the most common method for liquefaction assessment in Christchurch, and issues have been identified with the soil behaviour type, liquefaction potential and vertical settlement estimates, particularly in the north-western suburbs of Christchurch where soils consist mostly of silts, clayey silts and silty clays. The CPT soil behaviour type often appears to over-estimate the fines content within a soil, while the liquefaction potential and vertical settlement are often calculated higher than those measured after the Canterbury earthquake sequence. To investigate these issues, laboratory work was carried out on three adjacent CPT/borehole pairs from the Groynes Park subdivision in northern Christchurch. Boreholes were logged according to NZGS standards, separated into stratigraphic layers, and laboratory tests were conducted on representative samples. Comparison of these results with the CPT soil behaviour types provided valuable information, where 62% of soils on average were specified by the CPT at the Groynes Park subdivision as finer than what was actually present, 20% of soils on average were specified as coarser than what was actually present, and only 18% of soils on average were correctly classified by the CPT. Hence the CPT soil behaviour type is not accurately describing the stratigraphic profile at the Groynes Park subdivision, and it is understood that this is also the case in much of northwest Christchurch where similar soils are found. The computer software CLiq, by GeoLogismiki, uses assessment parameter constants which are able to be adjusted with each CPT file, in an attempt to make each more accurate. These parameter changes can in some cases substantially alter the results for liquefaction analysis. The sensitivity of the overall assessment method, raising and lowering the water table, lowering the soil behaviour type index, Ic, liquefaction cutoff value, the layer detection option, and the weighting factor option, were analysed by comparison with a set of ‘base settings’. The investigation confirmed that liquefaction analysis results can be very sensitive to the parameters selected, and demonstrated the dependency of the soil behaviour type on the soil behaviour type index, as the tested assessment parameters made very little to no changes to the soil behaviour type plots. The soil behaviour type index, Ic, developed by Robertson and Wride (1998) has been used to define a soil’s behaviour type, which is defined according to a set of numerical boundaries. In addition to this, the liquefaction cutoff point is defined as Ic > 2.6, whereby it is assumed that any soils with an Ic value above this will not liquefy due to clay-like tendencies (Robertson and Wride, 1998). The method has been identified in this thesis as being potentially unsuitable for some areas of Christchurch as it was developed for mostly sandy soils. An alternative methodology involving adjustment of the Robertson and Wride (1998) soil behaviour type boundaries is proposed as follows:  Ic < 1.31 – Gravelly sand to dense sand  1.31 < Ic < 1.90 – Sands: clean sand to silty sand  1.90 < Ic < 2.50 – Sand mixtures: silty sand to sandy silt  2.50 < Ic < 3.20 – Silt mixtures: clayey silt to silty clay  3.20 < Ic < 3.60 – Clays: silty clay to clay  Ic > 3.60 – Organics soils: peats. When the soil behaviour type boundary changes were applied to 15 test sites throughout Christchurch, 67% showed an improved change of soil behaviour type, while the remaining 33% remained unchanged, because they consisted almost entirely of sand. Within these boundary changes, the liquefaction cutoff point was moved from Ic > 2.6 to Ic > 2.5 and altered the liquefaction potential and vertical settlement to more realistic ii values. This confirmed that the overall soil behaviour type boundary changes appear to solve both the soil behaviour type issues and reduce the overestimation of liquefaction potential and vertical settlement. This thesis acts as a starting point towards researching the issues discussed. In particular, future work which would be useful includes investigation of the CLiq assessment parameter adjustments, and those which would be most suitable for use in clay-rich soils such as those in Christchurch. In particular consideration of how the water table can be better assessed when perched layers of water exist, with the limitation that only one elevation can be entered into CLiq. Additionally, a useful investigation would be a comparison of the known liquefaction and settlements from the Canterbury earthquake sequence with the liquefaction and settlement potentials calculated in CLiq for equivalent shaking conditions. This would enable the difference between the two to be accurately defined, and a suitable adjustment applied. Finally, inconsistencies between the Laser-Sizer and Hydrometer should be investigated, as the Laser-Sizer under-estimated the fines content by up to one third of the Hydrometer values.

Images, UC QuakeStudies

A residential property in Bexley with an overgrown garden. Dried liquefaction silt still covers the ground. The photographer comments, "Today I took a drive around the residential area between Bexley and New Brighton. It was a stark reminder to be thankful for the situation we're in and perhaps not complain too much that our garden wall hasn't yet been rebuilt".

Images, UC QuakeStudies

An advertising poster outside Minx Dining Room and Bar on Lichfield Street depicts Katy Perry in a bird cage. The photographer comments, "One of the sites you will see on the Christchurch CBD red zone tour".

Images, UC QuakeStudies

A car on Rowses Road has its entire front half embedded in liquefaction after falling into a sink hole. Two other cars have their wheels stuck in the silt. The photographer comments, "Perhaps the most impressively stuck car was this small silver hatchback that went head first into a large hole in a street just off Shortland Street (between Shortland and Breezes Road) in Aranui. The rear hatch was open when we came across it. Apparently there had been one person and a dog inside but they managed to escape. The silt has now settled around and inside the car, making the vehicle an intimidating monument to the earthquake".

Images, UC QuakeStudies

A car on Rowses Road has its entire front half embedded in liquefaction after falling into a sink hole. Behind it, another car has its wheels stuck in the silt. The photographer comments, "Perhaps the most impressively stuck car was this small silver hatchback that went head first into a large hole in a street just off Shortland Street (between Shortland and Breezes Road) in Aranui. The rear hatch was open when we came across it. Apparently there had been one person and a dog inside but they managed to escape. The silt has now settled around and inside the car, making the vehicle an intimidating monument to the earthquake".

Images, UC QuakeStudies

A car on Rowses Road has its entire front half embedded in liquefaction after falling into a sink hole. Two other cars have their wheels stuck in the silt. The photographer comments, "Perhaps the most impressively stuck car was this small silver hatchback that went head first into a large hole in a street just off Shortland Street (between Shortland and Breezes Road) in Aranui. The rear hatch was open when we came across it. Apparently there had been one person and a dog inside but they managed to escape. The silt has now settled around and inside the car, making the vehicle an intimidating monument to the earthquake".

Images, UC QuakeStudies

A car on Rowses Road has its entire front half embedded in liquefaction after falling into a sink hole. Behind it, another car has its wheels stuck in the silt. The photographer comments, "Perhaps the most impressively stuck car was this small silver hatchback that went head first into a large hole in a street just off Shortland Street (between Shortland and Breezes Road) in Aranui. The rear hatch was open when we came across it. Apparently there had been one person and a dog inside but they managed to escape. The silt has now settled around and inside the car, making the vehicle an intimidating monument to the earthquake".

Images, UC QuakeStudies

A car on Rowses Road has its entire front half embedded in liquefaction after falling into a sink hole. Behind it, another car has its wheels stuck in the silt. The photographer comments, "Perhaps the most impressively stuck car was this small silver hatchback that went head first into a large hole in a street just off Shortland Street (between Shortland and Breezes Road) in Aranui. The rear hatch was open when we came across it. Apparently there had been one person and a dog inside but they managed to escape. The silt has now settled around and inside the car, making the vehicle an intimidating monument to the earthquake".

Images, UC QuakeStudies

A residential property in Bexley with boarded up windows and an overgrown garden. Dried liquefaction silt still covers the ground. The photographer comments, "Today I took a drive around the residential area between Bexley and New Brighton. It was a stark reminder to be thankful for the situation we're in and perhaps not complain too much that our garden wall hasn't yet been rebuilt".