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ORIGINAL ARTICLEFormation of layered fracture and outburst in stratumsX. B. Lu • X. H. Zhang • L. LuReceived: 18 December 2013/Accepted: 17 October 2014/Published online: 1 November 2014? Springer-Verlag Berlin Heidelberg 2014Abstract Layered fracture and outburst are two typicaltypes of failures in a stratum that occur in many cases, suchas liquefaction of sand, mining of coal, and dissociation ofgas hydrate. The formation of both the failures is analyzedusing the mathematical model based on the three-phasemedia. It is found that both failures occur once the porepressure is high enough to cause the crashing and breakageof the skeleton. In other words, the formation conditionsare related to the tensile strength of the stratum and theoverburden. The fracture expands and shrinks along withthe penetration and drainage of pore water and gas; out-burst stops gradually as the energy dissipates in thestratum.Keywords Layered fracture ? Outburst ? Gas hydrate ?LiquefactionIntroductionLayered fracture [also called water film (Fig. 1a)] andoutburst in soil stratum occur in many cases, such as in theliquefaction of sand [also called soil boiling in liquefactionsand (Fig. 1b)] (Huang and Jiang 2010; Huang and Yu2013; Lu and Cui 2004) in the mining of coal, and duringthe dissociation of gas hydrate. Layered fracture is a gap ofwater or gas in stratum and often spreads over a large area.Outburst is strong eruption of soil–water/gas mixture froma hole or a vertical fracture in the stratum like volcanicexplosion (Lu et al. 2006; Brennan and Madabhushi 2005).Water film is first observed in liquefied sand containingan impermeable seam accompanying slope failures inearthquakes (Seed 1987), and its formation in stratifiedsand has been revealed by shake table tests (Kokusho1999) and centrifuge tests (Fiegel and Kutter 1994).Moreover, it is found that the film develops just beneath thefine sand layer and generally forms the sliding surface ofslope. Zheng et al. (2001) presented a model consideringthe erosion and re-deposition of fine grains in skeleton.They thought water films could be formed by the magni-fication of inhomogeneity through the transport of the finegrains (Zheng et al. 2001; Lu and Cui 2010). Malvick et al.(2008) discussed the development of water film using theconcept of shear localization. But in many cases, the stra-tum bears no shearing.Sand boiling results from liquefaction, which is aneruption of sand–water mixture out onto the ground sur-face, often occurring during/after earthquake. For example,sand boiling has been found in many sites during the 2008Wenchuan earthquake and 1976 Tangshan earthquake inChina. Huang and Yu (2013) classified the sand boilingformation into two categories: flat-cone sand volcanoes andliquefied sands erupting on the surface through existingcracks (Huang and Jiang 2010; Huang and Yu 2013). Whenthe sand boils, it really liquefies and the hydraulic gradientis equal or larger than the over burden pressure (Wang1997).In the case of coal mining with complex geology andlow strength of coal, the mines prone to fracture or burstdepend on the tectonic and gas pressure. Experimentsshowed that the coal mine can be broken and gasified intooutburst when the gas pressure is much higher than itsX. B. Lu (&) ? X. H. ZhangInstitute of Mechanics, Chinese Academy of Sciences,Beijing 100190, Chinae-mail: xblu@imech.ac.cnL. LuSchool of Science, China University of Mining and Technology,Beijing 100083, China123Environ Earth Sci (2015) 73:5593–5600DOI 10.1007/s12665-014-3813-5