Effect of buried depth and diameter on uplift of underground structures in liquefied soils

In an earthquake, underground structures located in liquefiable soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated soil. The uplift displacement of an underground structure in liquefiable soil deposit can be affected by the buried depth and size of the structure. Dynamic centrifuge tests have been carried out to investigate the influence of these factors by measuring the uplift displacement of shallow model circular structures. Ratios for the buried depth and diameter effects of the structure are introduced to compare the uplift displacement in different soil and earthquake conditions. With the depth effect and diameter effect ratios, the uplift displacement of a buoyant structure in liquefiable soil can also be estimated based on performance of similar structures in comparable soil condition and subjected to a similar earthquake event. © 2012 Elsevier Ltd.

Effect of soil conditions on uplift of underground structures in liquefied soil

In an earthquake, underground structures located in liquefiable soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated soil. Such uplift response of the buoyant structure is influenced by the soil it is buried in. In the case of a liquefiable soil deposit, the soil can lose its shear strength significantly in the event of an earthquake. If the soil liquefies fully, the buoyant structure can float towards the soil surface. However, a partly liquefied soil deposit retains some of its initial shear strength and resists the uplift. This paper discusses the different soil conditions and their influence on the uplift response of buoyant structures. © 2012 World Scientific Publishing Company.

Extreme sensitivity of graphene photoconductivity to environmental gases.

Graphene is a single layer of covalently bonded carbon atoms, which was discovered only 8 years ago and yet has already attracted intense research and commercial interest. Initial research focused on its remarkable electronic properties, such as the observation of massless Dirac fermions and the half-integer quantum Hall effect. Now graphene is finding application in touch-screen displays, as channels in high-frequency transistors and in graphene-based integrated circuits. The potential for using the unique properties of graphene in terahertz-frequency electronics is particularly exciting; however, initial experiments probing the terahertz-frequency response of graphene are only just emerging. Here we show that the photoconductivity of graphene at terahertz frequencies is dramatically altered by the adsorption of atmospheric gases, such as nitrogen and oxygen. Furthermore, we observe the signature of terahertz stimulated emission from gas-adsorbed graphene. Our findings highlight the importance of environmental conditions on the design and fabrication of high-speed, graphene-based devices.