Tools for estimation of the stability of unsupported trenches extending the mechanics of unsaturated soils

用于评估无支撑沟槽稳定性的工具，扩展了非饱和土的力学

• 批准号: RGPIN-2016-04354
• 负责人: Oh, WonTaek
• 金额: $ 1.75万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709177
• 关键词: Tools; estimation; stability; unsupported; trenches

Soil trenching is extensively used in geotechnical, mining, tunneling and geo-environmental infrastructure activities. Since soil trenching involves excavation work in limited spaces, soil trench failures can directly result in loss of lives. Although several provinces in Canada published guidebooks to emphasize occupational health and safety concerns related to fatalities associated with trench failures, a large number of worker deaths are still reported each year associated with soil trench failure. Safe height, Hsafe and stand-up time, Tstup are two key factors required in the design of soil trenches. Determination of Hsafe and Tstup requires active earth pressure and stability of soil trenches based on shear strength parameters of soils. Soil trenches are typically excavated into the soils in a state of unsaturated condition. Due to this reason, the existing approaches to estimate Hsafe and Tstup may not be reasonable since they do not consider the variation of mechanical properties of soils with respect to the change in soil moisture (or matric suction). Several researchers attempted to investigate the stability of unsaturated soil trenches taking into account matric suction; however, their research was limited to an investigation of the influence of rainfall infiltration on the Hsafe and Tstup. Currently, no approach is available to estimate Hsafe and Tstup of unsaturated soil trenches considering various practical scenarios simultaneously, such as rainfall infiltration, angles of side-slope/soil surface, different types of surcharge on the soil surface, and seepage of water through the side-slope of soil trenches. The proposed research will focus on developing simple yet rigorous tools to estimate Hsafe and Tstup of unsaturated soil trenches based on laboratory tests and coupled hydro-mechanical analyses. In addition, methodology or protocols to design soil nailings in unsaturated soil trenches will also be investigated, taking account of the aforementioned practical scenarios. The proposed design tools will be validated through large-scale tests in the field. This research will result in a design manual by working with various construction/design agencies, health and safety associations in Canada, and a Canadian Foundation Engineering Manual. Especially, in highly populated areas, construction of superstructures or replacements of old pipeline systems are very challenging due to limited work spaces. In this case, the design of engineering shoring is vital to support earth, water and adjacent structures. This proposed research is expected to be effectively used to design the engineering shoring considering various practical scenarios with and without soil reinforcement techniques. The proposed research will involve 5 HQPs (4 Master's and 1 PhD students) who will study unsaturated soil trenches through both laboratory tests and numerical modeling.

土壤挖沟广泛应用于岩土工程、采矿、隧道开挖和地质环境基础设施活动。由于土沟开挖涉及在有限空间内进行挖掘工作，土沟故障可能直接导致人员伤亡。尽管加拿大的几个省份出版了指南，强调与沟渠破坏相关的死亡相关的职业健康和安全问题，但每年仍然有大量工人因土沟破坏而死亡的报道。 安全高度 Hsafe 和站立时间 Tstup 是土沟设计中所需的两个关键因素。 Hsafe 和 Tstup 的确定需要基于土壤抗剪强度参数的主动土压力和土沟稳定性。土沟通常在不饱和状态下挖掘到土壤中。因此，现有的估计 Hsafe 和 Tstup 的方法可能不合理，因为它们没有考虑土壤力学特性随土壤湿度（或基质吸力）变化的变化。几位研究人员试图在考虑基质吸力的情况下研究非饱和土沟槽的稳定性；然而，他们的研究仅限于调查降雨入渗对 Hsafe 和 Tstup 的影响。 目前，还没有一种方法可以同时考虑多种实际情况，例如降雨入渗、边坡/土表面角度、土表面不同类型的堆载以及水通过土沟边坡的渗漏等，来估算非饱和土沟的Hsafe和Tstup。拟议的研究将侧重于开发简单而严格的工具，以基于实验室测试和耦合流体力学分析来估计非饱和土沟槽的 Hsafe 和 Tstup。此外，考虑到上述实际情况，还将研究在非饱和土沟中设计土钉的方法或协议。所提出的设计工具将通过大规模的现场测试进行验证。 这项研究将通过与加拿大各建筑/设计机构、健康和安全协会合作编写一份设计手册，以及一份加拿大基础工程手册。特别是在人口稠密的地区，由于工作空间有限，上层建筑的建造或旧管道系统的更换非常具有挑战性。在这种情况下，工程支撑的设计对于支撑土壤、水和邻近结构至关重要。这项研究预计将有效地用于设计工程支撑，考虑到有或没有土壤加固技术的各种实际情况。 拟议的研究将涉及 5 名 HQP（4 名硕士生和 1 名博士生），他们将通过实验室测试和数值模拟研究非饱和土沟槽。