Effectiveness of distributed temperature measurements for early detection of piping in river embankments

Abstract

Abstract.Internal erosion is the cause of a significant percentage of failure and incidents involving both dams and river embankments in many countries. In the past 20 years the use of fibre-optic Distributed Temperature Sensing (DTS) in dams has proved to be an effective tool for detection of leakages and internal erosion. This work investigates the effectiveness of DTS for dike monitoring, focusing on early detection of backward erosion piping, a mechanism that affects the foundation 10 layer of structures resting on permeable, sandy soils. The paper presents data from a piping test performed on a large-scale experimental dike equipped with a DTS system together with a large number of accompanying sensors. The effect of seepage and piping on the temperature field is analysed, eventually identifying the processes that cause the onset of thermal anomalies around piping channels and thus enable their early detection. Making use of dimensional analysis, the factors that influence that thermal response of a dike foundation are identified. Eventually some tools are provided that can be helpful for 15 the design of monitoring systems and for interpretation of temperature data.

Errors in finite element analysis of backward erosion piping

“…The head profile upstream of the pipe tip was closely approximated by all of the FE analysis using hexahedral pipe elements. The head distribution and resulting hydraulic gradients and seepage velocities upstream of the pipe tip are of great interest as most numerical models evaluate pipe progression using these values 12,20,21,24,25,28,33,38 . As one can see from Fig.…”

“…This analog has been used by many authors for simulating the BEP process (e.g., Refs. 12,26,27,33). The finite element program for steady-state groundwater flow from Smith and Griffiths 34 was modified for this purpose.…”

A Review of Distributed Fibre Optic Sensors for Geo-Hydrological Applications

“…Although most of the applications and papers dealt with short-term measurement campaigns [107,137] or experiments in physical models [123,125,138,139], there are some examples testifying years-long measurement campaigns [100,106,140]-all employing Raman-DTSs. For example, within the framework of the project IJkdijk, Beck et al [106] analysed the data collected over a measurement period of one year to test the reliability of long-term data analysis approaches.…”

“…Retrofitting of existing levees has also been proposed by burying the cable in the soil, in a narrow trench dug at the toe (see Figure 10) or under the surface of the downstream slope. Specific depths and precise locations must also be defined after careful site characterisation, in order to maximise the chance of capturing potential leakages [139]. The use of engineered geotextiles and geogrids has been extensively addressed by several authors and tested in physical models of embankments toward the aim of making the installation easier [138,[141][142][143][144][145].…”