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Soil Mechanics
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Figure 15.30 shows a warning sign advising swimmers to keep away from some sandy piles surrounded by quicksand. Quicksand forms when loose sand that is saturated with water becomes agitated—perhaps when someone walks on it. The water in the sand cannot escape, so effective stress is reduced and the sand flows like a liquid and cannot support weight. Quicksand is often associated with springs because upward flowing water can keep sand particles in suspensions, but quicksand also forms in standing water.
Geotechnical Reconnaissance of the 2016 ML6.6 Meinong Earthquake in Taiwan
Published in Journal of Earthquake Engineering, 2018
Chi-Chin Tsai, Shang-Yi Hsu, Kuo-Lung Wang, Hsuan-Chih Yang, Wei-Kuang Chang, Chia-Han Chen, Yu-Wei Hwang
A common manifestation of liquefaction is the formation of sand boils at the ground surface by squeezing water through ground cracks or, in some cases, by the development of quicksand-like conditions over substantial areas as shown in Fig. 6. As a result, structures at ground surface present settlement or tilt because of the loss of bearing capacity. Based on such surface evidence, liquefaction was identified at six locations, as shown in Fig. 2. Annan (LI1), Xinshi (LI2), Wenhe (LI3), and Zhengju (LI4) are residential areas, and liquefaction led to different levels of structural damage. Dawan E (LI5) and Xinhua (LI6) are free field sites located in farm lands; thus, no damage was reported. The estimated PGA of these sites is listed in Table 1. The shaking levels at these locations were moderate (PGA was ~0.20–0.25 g), but the consequences were significant. The most severely damaged areas were Annan, Xinshi, and Wenhe sites, where substantial settlement and tilt of buildings were reported. The Xinhua site, even without damage, had been liquefied in the past. The observations of these sites are elucidated below.
Characteristics and causes of cracking and damage of shield tunnel segmented lining in construction stage – a case study in Shanghai soft soil
Published in European Journal of Environmental and Civil Engineering, 2018
Yubing Yang, Biao Zhou, Xiongyao Xie, Chao Liu
Figure 2 presents the ground profile along the tunnel alignment. Mixed-face conditions of Quaternary Pleistocene deposit (Q32) with a length of 360 m were encountered during the earth pressure balanced shield machine passing R72 (‘R’ is short for ‘ring’). This mixed-ground comprises clay, sandy silt and silty fine sand. Table 2 shows the soil profile from a 50-m-deep borehole, as well as the typical geotechnical parameters obtained from the soil tests of corresponding stratum. The soil layers ⑦-1 (sandy silt) and ⑦-2 (silty fine sand) are the first confined aquifers, where quicksand may happen under certain hydrodynamic pressure. Tunnel face instability is highly likely in the two strata. Moreover, the interface between the two strata with different stiffness (e.g. layers ⑥ and ⑦-1) would induce ‘head up’ or ‘head down’ of shield machine, making it difficult to maintain the stability of tunnel face. It is worth noting that the cover depth of the tunnel varies from 19 to 35 m at the side of Pudong district, giving rise to a tunnel slope of 29.4‰.
Retrofitting urban drainage infrastructure: green or grey?
Published in Urban Water Journal, 2018
David Peter Dolowitz, Sarah Bell, Melissa Keeley
While green infrastructure is an element of Glasgow’s stormwater plan, the core of Scottish Water’s development plan is the construction of several large storage and conveyance tunnels under the city, the largest of which is a three-mile tunnel to run from Queen’s Park to Craigton industrial estate. Scottish Water describes the £100 million project as:The biggest investment in the network since Victorian times, the upgrade will improve river water quality and the natural environment of the River Clyde and its tributaries, enable the Greater Glasgow area to grow and develop, alleviate sewer flooding and deal with the effects of increased rainfall and climate change. (Scottish Water 2013)The Scottish Water preference for ponds, basins and large-scale underground storage tunnels is in part due to existing urban infrastructure, soil type and variation in Glasgow’s average rainfall. Glasgow is built on a complex mix of soils including: wet mud and sand, boulder clay, solid rock, shale, sandstone and quicksand. Monthly average rainfall ranges from highs of 130–140 mm in December and January to lows of 60–65 mm per month between April and June. As such, while SuDS are recommended or required in many documents, the primary techniques tend not to include infiltration and site-specific practices (as commonly found in the US).