The use of “simplified procedures” for the study of lateral spreading could be misleading, and it is debatable whether or not lateral spreading case histories should be included in liquefaction triggering databases. In this context, the 2010-2011 Canterbury Earthquake Sequence (CES) provides several examples of liquefaction and lateral spreading, as identified by the post-earthquake reconnaissance campaigns. Major to moderate lateral spread displacements were observed in the proximity of the Avon River in Christchurch (New Zealand), within about 100-200 m from the fluvial axis and with maximum crack widths of over 200 mm. This paper documents the results of a series of seismic dilatometer tests (SDMT) performed along a section that crosses the Wainoni suburb from the Avon River, where lateral spreading was severe, to farther from the river, where liquefaction features were relatively minor during the CES. Profiles of the SDMT parameters, especially of the horizontal stress index (KD), show significantly higher values when the sounding is close to the river but insignificant changes at greater distances from the river. Increases in KD may be related to an increase in the lateral stress in the subsoil induced by compression of the lateral spread mass near the river. Because the flat dilatometer test (DMT) is more sensitive to changes in lateral stress than other in-situ tests, this increase in lateral stress during lateral spreading may not have been recognized using other test methods. Although post-liquefaction in-situ testing is commonly used to develop liquefaction triggering databases, the observed increase in KD suggests that the DMT-based triggering curves should only include post-liquefaction case histories with no lateral spreading. Similar precautions may be necessary for other in-situ tests after additional research.
Influence of the lateral spreading on the seismic dilatometer (SDMT) parameters: a case study in Christchurch, New Zealand
Monaco, Paola;
2024-01-01
Abstract
The use of “simplified procedures” for the study of lateral spreading could be misleading, and it is debatable whether or not lateral spreading case histories should be included in liquefaction triggering databases. In this context, the 2010-2011 Canterbury Earthquake Sequence (CES) provides several examples of liquefaction and lateral spreading, as identified by the post-earthquake reconnaissance campaigns. Major to moderate lateral spread displacements were observed in the proximity of the Avon River in Christchurch (New Zealand), within about 100-200 m from the fluvial axis and with maximum crack widths of over 200 mm. This paper documents the results of a series of seismic dilatometer tests (SDMT) performed along a section that crosses the Wainoni suburb from the Avon River, where lateral spreading was severe, to farther from the river, where liquefaction features were relatively minor during the CES. Profiles of the SDMT parameters, especially of the horizontal stress index (KD), show significantly higher values when the sounding is close to the river but insignificant changes at greater distances from the river. Increases in KD may be related to an increase in the lateral stress in the subsoil induced by compression of the lateral spread mass near the river. Because the flat dilatometer test (DMT) is more sensitive to changes in lateral stress than other in-situ tests, this increase in lateral stress during lateral spreading may not have been recognized using other test methods. Although post-liquefaction in-situ testing is commonly used to develop liquefaction triggering databases, the observed increase in KD suggests that the DMT-based triggering curves should only include post-liquefaction case histories with no lateral spreading. Similar precautions may be necessary for other in-situ tests after additional research.Pubblicazioni consigliate
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