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Supporting data for "Learning More Lessons from a Catastrophic Man-made Slope Failure Disaster in Shenzhen by Physical Experiments"

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posted on 18.08.2020 by Lukas Albert Rahardjo
Abstract
Landslide on 20 December 2015 in Shenzhen is essentially fill soil from excavation activities. The soil fills were inside gourd-shaped bedrock. It buried 33 buildings with a minimum distance of 300 m to the fill slope toe within 13 minutes. The conventional theory underlying the mechanism of the cause of Shenzhen landslide are rainfall, liquefaction, geometry, absence of compaction, and excess pore water pressure. The catastrophes continuously take places even recent days. Hence, Yue Z.Q. [2008] proposed an alternative modeling theory for this source of the mechanism. Gas, which contributes the source of mechanism remains among the least studied.

Three peculiar elements in the Shenzhen landslide accounted. First, gentle slope angle of ~17.5°. Second, rainfall intensity in multilevel timeframe was low. Annual rainfall from 2013 to 2015 on average was 1965.7 mm. The total daily rainfall from October 7 to December 20, 2015 was 104.8 mm. Daily rainfall from December 15–19, 2015 was zero. Third, the amount of liquefied soil observed in the field was tremendously little compare to the slope volume. It suspected that adjoining leaked gas pipe spark the Shenzhen landslide [Yue Z.Q. 2018]. Present research introduced new experimental setups to investigate the possible conditions of the landslide. At first, observation carried out without gas involvement and according to pre-determined water content. Then, source of energy in form of gas are established. Two types of bedrocks created, 2D and 3D models with scale 1:900 and 1:1000, respectively. Ten different experiment conditions presented (A1, B1 – B3, C1 – C6) under three major types of tests. First and second are 2D and 3D model bedrock with soil. Third, 3D model bedrock with hydrogen peroxide solution (H2O2(aq)) and cement. Initial applied air pressure were 2 ~ 4 kPa for the first two types.

Bottom soil layers designed as impermeable as possible by full saturation. While top soil layers designed more than its liquid limit. Entire experiments revealed there is no deformation with the absence of gas pressure. Non-linear pressure of air applied. Maximum pressure were 85kPa (A1), 112kPa (B1), 235kPa (B2) and 240kPa (B3). Numerous deformation detected. Estimated 6.2% (A1), 29.47% (B1), 155% (B2), and 167% (B3) from total initial area. The results are reasonable compared to 137% of the same ratio from (Xu et al., 2017) and 169% from (Wang et al., 2017). Comparatively, supporting tests performed by ejection of piston from steel cylinder. The result show that the maximum height of ejecting piston (0.27 – 0.95 m) and velocity (2.29 – 4.32 m/s). The test results indicated pressurized gas contributed in the magmatic explosive volcanoes concede with available theory of gas by Yue Z.Q. [2008]. One example is in the case of 8 gram H2O2(aq). Total mass of 1.17 gram Oxygen could rocket up 285.90 gram steel piston. It flew for 34cm high.

Like water, gas is a fluid material and has no shear strength. Therefore, gas material and gas pressure infilled in soils can reduce soil effective strength, which can induce soil slope instability. Thus, modeling of geo-hazard phenomena shall include the useful studies [Yue Z.Q., 2008 – 2018].

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