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Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
From the point of view of the transfer function, stable systems have closed-loop transfer functions with only left half-plane poles, where a pole is defined as a value of s that causes F(s) to be infinite, such as a root of the denominator of a transfer function. Unstable systems have closed-loop transfer functions with at least one right half-plane pole and/or poles of multiplicity greater than one on the imaginary axis. Marginally stable systems have closed-loop transfer functions with only imaginary axis poles of multiplicity one and left half-plane poles. Stability is the most important system specification. An unstable system cannot be designed for a specific transient response or steady-state error requirement. Physically, instability can cause damage to a system, adjacent property, and human life. Many times, systems are designed with limit stops to prevent total runaway.
Factors affecting rock mass response to mining
Published in Tadeusz Szwedzicki, Rock Mass Response to Mining Activities, 2018
Factors contributing to rock mass response leading to damage are structural features and rock mass mechanical properties, and in situ and mining-induced stress (Fig. 2.1). The figure also incorporates the role of failure criteria and refers to ground control techniques. Rock mass response can indicate stability or instability. Stability refers to open span of excavations, self-support, optimal distance between excavations, stable pillars, etc. Instability, for example, can result in ground collapse, rock mass fragmentation, seismic activity, closure of excavations, slope movement, inundation, and failure of tailings storage facilities.
Fundamentals of ground improvement systems
Published in Hsai-Yang Fang, John L. Daniels, Introductory Geotechnical Engineering, 2017
Hsai-Yang Fang, John L. Daniels
General discussion: Natural causes of ground instability include tectonic movements, earthquakes, geothermal events, floods, wetting–drying, and freezing– thawing cycles, flora–fauna as well as other geological hazards. Soil responds to these causes in various ways, according to the type, mineralogy, local environment, and so on. Earthquakes, for example, affect the behavior of granular soils like sand and gravel dramatically. These soils provide adequate bearing capacity under ordinary circumstances, but may liquefy and have larger settlement during an earthquake.
An insight into failure of iron ore mine tailings dams
Published in International Journal of Mining, Reclamation and Environment, 2023
Francis Otieno, Sanjay Kumar Shukla
Slope instability can be prevented by directly observing tailings dam embankment or adjacent slopes for failure indicators such as cracking in the crest or slope face, settlement of the crest, damaged infrastructure, and changes in downstream water levels or quality. Moreover, instruments can also be utilised to monitor and assess slope instability. These may include extensometer to monitor settlement profile, slope stability radar to monitor surface movements, inclinometer to monitor and assess angular rotation; and piezometers to monitor pore water pressure [56]. Hence, monitoring enables identification of weaker areas that are likely to fail and appropriate remediation steps such as construction of buttresses around these areas, taken to strengthen the dam and avoid failure. Even though the use of geosynthetics to reinforce foundations and embankment slopes has been on the rise over the past few decades [86,87], they have not been accepted as readily as in the general construction market. However, they are increasingly getting accepted as operators begin to understand the advantages associated with the use of these polymeric materials [88,89]. Geosynthetic reinforcement improves stability, shear capacity and bearing capacity of the soil [87,90,91]. The use of geotextile tubes with suitable pore diameter, for example, has the effect of shortening the consolidation time of tailings, thus improving stability of the dam [87]. By incorporating geosynthetics into the structural frame of tailings dams, tailings impoundments become safer and therefore the risk of failure is reduced.
Stability of double-step muck slope under different overload conditions
Published in European Journal of Environmental and Civil Engineering, 2021
Wenqiang Chen, Yingjie Song, Zhibin Wu, Jiangbo Zeng, Changdong Li
In addition to stability analyses of CSW landfill slopes, studies of the causes of the failure of CSW landfill slopes also have practical significance, the results of which help to identify and mitigate potential risks. Many studies have reported a number of causes for the instability of conventional slopes, such as natural hill slopes and man-made cut slopes; these causes mainly include soil properties, rainfall, fluctuations in soil water and groundwater, earthquakes and human engineering activities, such as overloads (Iverson, 2000; Ni, Wang, Zhang, & Lin, 2016; Peng, Wang, Wang, & Zhang, 2017; Wang, Tang, Zhang, Li, & Huang, 2017; Yin, Wang, & Sun, 2009). For waste landfill slopes, Huang and Fan (2016) summarised the external and internal factors that affect the stability of landfills. The external factors were mainly divided into earthquakes, rainfall, toe excavation and overload. Moreover, the overload generated by poorly managed operations was found to increase the potential sliding force and decrease the stability of landfills. Hence, it is important and meaningful to conduct studies of the performance of landfill slopes subjected to overload conditions. Although several researchers have reported the failure of landfills caused by overload issues (Eid, Stark, Evans, & Sherry, 2000), detailed and comprehensive studies of the adverse effects of different overload conditions on the performance of CSW landfill slopes are still required, especially for landfills with complex geometries, such as double-step or multistep slopes.
Reconnaissance Report on Geotechnical Engineering Aspect of the 2015 Gorkha, Nepal, Earthquake
Published in Journal of Earthquake Engineering, 2019
Geotechnical earthquake researchers and practitioners may learn following lessons from the earthquake: Reassessment of the design and construction practices of Nepal may be necessitated. This study revealed the importance of carefully considering site conditions such as soil types and topography that have not been considered in Nepal National Building Code.It is critical to identify the sites that are prone to geotechnical failure due to landslides, fault displacements, slope instability, liquefaction, and so on. Determination of appropriate land use should then be guided via the identified risk map.Site-specific design of building structures with adequate strength, stiffness, ductility, and redundancy in areas subject to significant earthquake forces is important. Upgrade of seismic design should be carried out on a regular basis and should be implemented in new structures. Schools, hospitals, police and fire stations, and lifeline services especially those located on weak subsoils, site subject to geologic hazards should be relocated or retrofitted to meet the requirement of maintaining functions after an earthquake.A network of monitoring earthquake motions is vitally important. The lack of a network makes it difficult to quantify the motions at various regions in the valley or to characterize the local site response.