Reply to the two discussions on my paper "An alternative mechanism of pile failure in liquefiable deposits during earthquakes"
This paper proposes an alternative mechanism of pile failure in liquefiable deposits during earthquakes. This failure mechanism, based on pile buckling, is formulated by back-analysing 14 case histories of pile foundation performance during earthquakes and verified using dynamic centrifuge tests. A new parameter, the slenderness ratio of a pile, is introduced to classify pile performance in liquefiable soils. This parameter fits very well both the reported case histories and the centrifuge test results.
Simplified Analyses of Dynamic Pile Response Subjected to Soil Liquefaction and Lateral Spread Effects
Pore water pressures greater than effective soil stress and subsequent liquefaction are known to occur in saturated sand deposits subjected to earthquake excitations. Liquefaction of soils can result in a reduction of soil strength and yields large settlement via lateral spreading. For superstructures supported on pile foundations embedded in such soils, these effects can be devastating. For example, the 1964 Niigata earthquake in Japan damaged the foundation piles under one of the piers of the 12 spans, 207 meter long Showa Bridge. After the earthquake, an excavation survey of damaged piles indicated that bending failure occurred due to the lateral spreading of river bed soils (Hamada, 1992). Similarly, in the 1994, when Northridge earthquake occurs, river bank areas between Santa Clarita and Fillmore, Highway 23 crosses over the Santa Clara River, where sand boils were observed near a bridge pier. Cracks induced by lateral spreading were found approximately 4.5 m away from the pier (Stephen et al., 2002). Afterward, in the 1995 Kobe Earthquake, quay walls along the coastline of Kobe moved up to several meters toward the sea as a result of lateral spreading (Tokimatsu and Asaka, 1998). Some papers also discuss liquefaction-induced lateral spread under the foundations of long-span bridges subjected to spatially-varying ground motions. (Abbas and Manohar 2002; Zerva and Zervas, 2002; Wang et al., 2004; Zerva 2009). More recent devastating earthquakes such as the March 2011 Tohoku earthquake in Japan and the January 2010 Haiti earthquake can be found and reported by EERI (Earthquake Engineering Research Institute) and USGS (United States Geological Survey).
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.