Laboratory characterization of Hostun RF sand at very low confining stresses

Proceedings of the Institution of Civil Engineers - Ground Impr

2010

Many typical liquefaction remediation techniques are not appropriate for application under existing buildings and more novel techniques are required. This paper describes centrifuge tests investigating the performance of cementation as a liquefaction remediation method. Two soil profiles with the same superstructure were tested under earthquake shaking. The first profile consisted of a deep layer of loose, liquefiable sand. The second comprised a shallow layer of loose sand overlying dense sand. Centrifuge tests were carried out with a cemented zone underneath the structure, through the full depth of the liquefiable layers and also partial depth. The superstructure was modelled as a single-degree-offreedom system. It is found that a cemented zone through the full depth of a liquefiable layer results in considerable reduction of structural settlements. Increased magnitude and higher frequency accelerations are transmitted to the structure but, depending on the building characteristics, it is likely that improved overall seismic performance can be achieved. Improvements in structural settlements can also be obtained with partialdepth remediation, if the depth of the cemented zone is greater than the depth of liquefaction. This type of remediation seems to have little effect on the accelerations transmitted to the structure.

Section: Model Preparationmentioning

confidence: 99%

Cementation liquefaction remediation for existing buildings

Proceedings of the Institution of Civil Engineers - Ground Impr

2010

“…The properties adopted for this sand are shown in Table 2 and the particle size distribution curve is shown in Figure 3. Derivation of these soil properties is given in Mitrani (2006), with the exception of the peak friction angle, which was determined by triaxial tests on a similar grade of Hostun sand, Hostun RF (Gay et al, 2003). The dense layers of sand were produced by pouring the sand with a very low flow rate and a large drop height.…”

Section: Model Preparationmentioning

confidence: 99%

Geomembrane containment walls for liquefaction remediation

Proceedings of the Institution of Civil Engineers - Ground Impr

2013

Ground improvement techniques can be adopted to prevent existing buildings built on liquefiable soils sustaining damage in future earthquakes. Impermeable geomembrane containment walls may be an economic and successful technique but their design and performance are currently not well defined or well understood for this application. This paper describes centrifuge testing carried out to investigate the performance of such containment walls as a liquefaction remediation method for a single degree of freedom frame structure. The results were compared with those from similar centrifuge testing carried out with the same structure founded on unimproved sand, to assess the effectiveness of the remediation method. It was found that the geomembrane containment walls tested were effective at reducing structural settlement and did not significantly increase the accelerations transmitted to the structure. Structural settlements were reduced primarily by mobilising hoop stress and preventing lateral soil movement. By preventing surface drainage, a decrease in the volume change of the foundation sand was also observed. In addition, the impermeability of the walls may be important as this prevented rapid migration of pore water from the free field to the foundation region.

“…3. Derivation of these soil properties is given in Mitrani [2006], with the exception of the peak friction angle which was determined by triaxial tests on a similar grade of Hostun sand, Hostun RF [Gay et al 2003]. Each model was constructed by air-pluviating sand into the deep ESB box and placing the instruments at the desired levels.…”

Section: Model Preparationmentioning

confidence: 99%

Rigid Containment Walls for Liquefaction Remediation

J. Earthquake and Tsunami

2012

Many typical ground improvement techniques that are used for liquefaction remediation, such as in situ densification, are not appropriate for application under existing buildings and more novel techniques are required. This paper describes centrifuge tests investigating the performance of rigid containment walls as a liquefaction remediation method. A simple frame structure, founded on a deep layer of loose, liquefiable sand was tested under earthquake shaking. Centrifuge tests were then carried out with containment walls around the base of the structure, extending through the full depth of the liquefiable layer and also partial depth.It is found that rigid containment walls can be very effective in reducing structural settlements primarily by preventing lateral movement of the foundation sand but the impermeability of the walls may also be important. Improvements in structural settlement are observed even when the walls do not extend through the full depth of the liquefiable layer, if the depth of the walls is greater than the depth of the free field liquefaction. In addition, it is found that the accelerations of the structure are not increased, provided there is no rigid, structural connection between the structure and the containment walls.