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A Landslide Warning System for a Soil Slope on Oahu

机译：瓦胡岛土壤边坡滑坡预警系统

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摘要

A landslide warning system for a 40-foot-high cut soil slope on Kalaniana'ole Highway was developed by performing a soil investigation, laboratory tests, installing monitoring instruments, developing and calibrating a transient hydrological flow model, using the calibrated model to predict moisture/suction response during a design storm, inputting these moisture/suction predictions into a slope stability analysis and establishing threshold values for the monitoring instruments.;The geotechnical investigation and index testing showed that the slope consists of a uniform reddish-brown, stiff to very-stiff, highly overconsolidated elastic silt (MH). Saturated consolidation tests were performed to obtain the saturated compression curve and the saturated hydraulic conductivity, which was determined to be 10-6 cm/s. A saturated multi-stage consolidated-drained triaxial shear test was performed to obtain the Hvorslev true friction angle and true cohesion, which was 27° and 18 kPa, respectively. Pressure plate and vapor sorption analyser tests were performed to obtain the unconfined soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF). Three constant water content isotropic compression (CWIC) tests were performed to obtain the Basic Barcelona Model (BBM) stiffness parameters and the porosity-dependent van Genuchten parameters. Constant water content triaxial shear tests (CWTS) were performed to obtain the BBM shear strength parameters, and the critical state friction angle which was estimated to be 37°. The BBM parameters were calibrated using the modified state-surface approach (Zhang and Lytton, 2009).;A 2D finite-element transient hydrological flow model was calibrated using the field measured suctions and water contents during a two-and-a-half-year period. A good fit between measured and predicted values for all sensors was obtained by modeling hysteresis and porosity-dependency in the SWCC and HCF. The calibrated model was then used to predict the slope response due to a 500-year design storm, and to establish landslide warning thresholds for the monitoring instruments. The predicted suctions and water contents during the design storm, and the porosity at each node estimated using the calibrated BBM stiffness parameters, were inserted into a slope stability analysis. The slope was deemed stable (FSmin~1.2) during a 500-year storm.;Amber and red thresholds were developed using Nicholson et al's (1999) traffic light approach for two tensiometers and two water content sensors based on the predicted suction and water content response during a 500-year storm and the maximum water contents and minimum suctions ever measured in the field. Proposed plans of action include: 1) cover the slope with a tarp or geomembrane to prevent further infiltration if the amber threshold is triggered, and 2) close the town-bound lane of Kalaniana'ole Highway if the red threshold is triggered.;Key findings include: (1) it is important for a transient hydrological flow model to account for SWCC and HCF hysteresis and porosity-dependency in order to predict field behaviour reliably; (2) Porosity-dependent SWCCs can be derived from constant water content isotropic compression tests along with the use of the Basic Barcelona Model stiffness parameters and a modified form of the van Genuchten (1980) equation; (3) Based on 2D slope stability analyses, the slope will survive a 500-year storm with a factor of safety ≈ 1.2.
机译：通过进行土壤调查，实验室测试，安装监测仪器，开发和校准瞬态水文流量模型，并使用校准后的模型进行预测，开发了针对Kalaniana'ole公路上40英尺高切土坡的滑坡预警系统。设计暴风雨期间的湿度/吸力响应，将这些湿度/吸力预测值输入到边坡稳定性分析中，并为监测仪器建立阈值;岩土工程研究和指数测试表明，该边坡由均匀的红棕色，硬到非常坚硬，高度固结的弹性淤泥（MH）。进行饱和固结测试以获得饱和压缩曲线和饱和水力传导率，确定其为10-6 cm / s。进行了饱和的多级固结排水三轴剪切试验，得到的Hvorslev真实摩擦角和真实内聚力分别为27°和18 kPa。进行了压力板和蒸气吸附分析仪测试，以获得无限制的土壤水特征曲线（SWCC）和水力传导率函数（HCF）。进行了三个恒定的含水量各向同性压缩（CWIC）测试，以获取基本巴塞罗那模型（BBM）的刚度参数和与孔隙度相关的van Genuchten参数。进行恒水含量三轴剪切试验（CWTS），以获得BBM剪切强度参数，以及临界状态摩擦角（估计为37°）。使用改进的状态表面方法对BBM参数进行校准（Zhang和Lytton，2009）.;在现场进行了两个半小时的测量，使用现场测得的吸力和水含量对二维有限元瞬变水文流模型进行了校准。年期。通过对SWCC和HCF中的磁滞和孔隙率相关性进行建模，可以获得所有传感器的测量值和预测值之间的良好拟合。然后使用校准后的模型来预测由于500年设计风暴而引起的边坡响应，并为监测仪器建立滑坡预警阈值。设计暴风雨期间的预测吸力和含水量，以及使用校准的BBM刚度参数估算的每个节点的孔隙度，都被插入到边坡稳定性分析中。在500年的暴风雨中，该坡度被认为是稳定的（FSmin〜1.2）。根据预测的吸力，使用Nicholson等人（1999）的交通信号灯方法针对两个张力计和两个含水量传感器开发了琥珀色和红色阈值500年暴风雨期间的水含量响应以及最大的水含量和最小的吸水量。拟议的行动计划包括：1）如果触发了琥珀色阈值，则用防水布或土工膜覆盖斜坡，以防止进一步的渗透； ​​2）如果触发红色阈值，则关闭Kalaniana'ole Highway的城镇边界车道。主要发现包括：（1）为了可靠地预测田间行为，瞬态水文流量模型必须考虑SWCC和HCF的滞后性和孔隙度依赖性。 （2）孔隙率相关的SWCC可以通过恒定水含量的各向同性压缩试验以及基本巴塞罗纳模型的刚度参数和van Genuchten（1980）方程的改进形式得出； （3）根据2D边坡稳定性分析，该边坡将在500年的暴风雨中幸存下来，其安全系数为＆ap; 1.2。

著录项

  • 作者

    Iwamoto, Melia K.;

  • 作者单位

    University of Hawai'i at Manoa.;

  • 授予单位 University of Hawai'i at Manoa.;
  • 学科 Civil engineering.
  • 学位 Ph.D.
  • 年度 2018
  • 页码 282 p.
  • 总页数 282
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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