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EireChch
Geotechnical
- Jul 25, 2012
- 1,309
Hello all,
I wanted to start this thread to get an idea on how geotechnical testing scopes vary for different regions. I will give you the standard geotech scope for residential builds in my region Auckland and Christchurch, New Zealand.
Auckland- typically the soils are silts with varying amounts of clay and sand. For a new residential building on a moderately steep slope we would do two hand drilled boreholes. One I the middle of the building platform and one on the downslope side say within 10m. Boreholes would be drilled to 3-5m depth with pilcon shear vane testing every 0.5m. The vane gives an undrained Cu. Scala penetrometer testing is extended from the base of the borehole which will sometimes encounter weathered silt/sand stone. Competent soils are encounters when 3 consecutive reading of 10blows/50mm is encountered. Cu x 5.14 gives an ult bearing for use in foundation design. 6-9 x Cu can be given for pile end bearing, depending of founding depth. A slide slope stability analysis is generally only done if the slope is greater than 14 degrees or if there is evidence to warrant.
Christchurch- as many of you may know Christchurch was hit by several large earthquakes over the last 3 years which has caused the guidelines to t rewritten to account for the liquefaction risk. For residential dwellings the guidelines require 1 CPT or machine borehole with SPT testing. Other supplementary deep testing e.g heavy dynamic probe can be used in conjunction with the CPT or MH. The data gathered from testing is used to undertake a liquefaction analysis under ULS (0.35g) and SLS(0.13g) seismic loading. The analysis gives vertical free filed settlement estimates which dictate the foundation system.There are generally 3 types of foundation systems 1)deep ground improvement i.e stone columns soil mixed columns 2) deep piles 3) shallow like foundations which are capable of being re-levelled following liquefaction induced settlement.
Would other engineers care to post the standard testing approaches for there regions. And feel free to quiz me on the above info. It was written from my I phone so please excuse speling mistakes.
I wanted to start this thread to get an idea on how geotechnical testing scopes vary for different regions. I will give you the standard geotech scope for residential builds in my region Auckland and Christchurch, New Zealand.
Auckland- typically the soils are silts with varying amounts of clay and sand. For a new residential building on a moderately steep slope we would do two hand drilled boreholes. One I the middle of the building platform and one on the downslope side say within 10m. Boreholes would be drilled to 3-5m depth with pilcon shear vane testing every 0.5m. The vane gives an undrained Cu. Scala penetrometer testing is extended from the base of the borehole which will sometimes encounter weathered silt/sand stone. Competent soils are encounters when 3 consecutive reading of 10blows/50mm is encountered. Cu x 5.14 gives an ult bearing for use in foundation design. 6-9 x Cu can be given for pile end bearing, depending of founding depth. A slide slope stability analysis is generally only done if the slope is greater than 14 degrees or if there is evidence to warrant.
Christchurch- as many of you may know Christchurch was hit by several large earthquakes over the last 3 years which has caused the guidelines to t rewritten to account for the liquefaction risk. For residential dwellings the guidelines require 1 CPT or machine borehole with SPT testing. Other supplementary deep testing e.g heavy dynamic probe can be used in conjunction with the CPT or MH. The data gathered from testing is used to undertake a liquefaction analysis under ULS (0.35g) and SLS(0.13g) seismic loading. The analysis gives vertical free filed settlement estimates which dictate the foundation system.There are generally 3 types of foundation systems 1)deep ground improvement i.e stone columns soil mixed columns 2) deep piles 3) shallow like foundations which are capable of being re-levelled following liquefaction induced settlement.
Would other engineers care to post the standard testing approaches for there regions. And feel free to quiz me on the above info. It was written from my I phone so please excuse speling mistakes.
