Performance of a propped retaining wall at the CTRL, Ashford

This thesis is based on the field monitoring of a propped bored pile retaining wall installed<br/>in an overconsolidated clay. Pile bending moments, prop loads, pore water pressures and<br/>lateral earth pressures were logged automatically at intervals of up to 5 minutes<br/>throughout construction (and for 4 years afterwards) and wall deflections were measured<br/>during construction, making this the most comprehensive instrumentation project of its<br/>kind.<br/>The magnitude of the over-read associated with the use of spade cells (used to measure<br/>lateral earth and pore water pressures) in overconsolidated deposits was determined by<br/>comparing readings from a spade cell aligned to measure vertical stress with the estimated<br/>overburden acting on it as the overburden was excavated. This study adds significantly to<br/>the previous data as spade cells have not previously been \lsed in the Atherfield Clay, and<br/>the performance of spade cells under a known changing load has not previously been<br/>measured in the field.<br/>Analysis of the changes in lateral stress and pore water pressure during the wall<br/>installation process showed significant reductions in horizontal stress during wall<br/>installation, reducing the ratio of effective horizontal to effective vertical stress, K, from<br/>about 1 to nearly the active condition. Following wall installation there was no further<br/>change in horizontal stress over a period of about 10 months, during which time no further<br/>construction work took place.<br/>Analysis of the data yielded good agreement between pile bending moments estimated<br/>from inclinometer and strain gauge measurements in the piles, and the onset of concrete<br/>cracking was identified. The components of strain measured in the reinforced concrete<br/>props due to shrinkage, creep and applied load were also identified, allowing prop loads to<br/>be estimated. A simple equilibrium calculation showed that these agree with the measured<br/>wall bending moments and total horizontal soil stresses, demonstrating the overall<br/>consistency of the data collected.<br/>Simple equilibrium analysis of the behaviour of the wall during construction shows that<br/>the soil stresses measured are compatible with the measured structural loads. The longterm<br/>horizontal soil stresses, bending moments and RC prop loads show no increase over<br/>the 6 years since construction began.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2006

Author dc:creator

• Clark, Jo

Advisor dc:contributor.advisor

• Richards, David