Listening to Infrastructure Early detection of seepage-induced - - PowerPoint PPT Presentation

Listening to Infrastructure

Early detection of seepage-induced internal erosion using acoustic emission monitoring

School of Architecture, Building and Civil Engineering

PhD candidate

Tiago Biller

Supervisors:

Dr Alister Smith Prof Neil Dixon

I. Silt with some clay, sand and gravel II. Selected sand, gravel end cobbles III. Miscellaneous fill IV. Selected, silt, sand, gravel and cobbles V. Rock fill

Morning of June 5th, 1976: leak from right abutment.

Teton Dam. Idaho, USA

93m high earth zoned embankment

(ICOLD, 2014)

Tiago Biller - t.biller@lboro.ac.uk School of Architecture, Building and Civil Engineering

Motivation

1

Mid-morning: leak had enlarged upwards through the dam Mid-day: further enlarged and widened leak under crest

(ICOLD, 2014)

• 14 deaths
• Up to US$1 billion property damage

Motivation

Tiago Biller - t.biller@lboro.ac.uk 2 School of Architecture, Building and Civil Engineering

Seepage-induced internal erosion

Goal: the detection internal erosion in its early stages, before serious damage has occurred

Tiago Biller - t.biller@lboro.ac.uk 3 School of Architecture, Building and Civil Engineering

Fannin and Slangen, 2014

Suffusion Suffosion Current monitoring techniques still do not offer viable early warning systems for seepage-induced internal erosion.

Acoustic emissions and internal erosion

Tiago Biller - t.biller@lboro.ac.uk 4 School of Architecture, Building and Civil Engineering

Koerner et al. (1981)

Experimental setting

Operation:

• Flow is induced by applying a constant hydraulic head
• Pressure is measured by manometers and pressure

transducers at two different heights along the specimen

• Water flow and eventual particle movement generate AE
• AE is transmitted through a waveguide and measured by

a sensor external to the specimen

• The signal is amplified, pre-filtered by a data acquisition

software and stored for further analysis

Tiago Biller - t.biller@lboro.ac.uk 5 School of Architecture, Building and Civil Engineering

Permeameter

Data processing and interpretation

Characterization of tested material Internal stability criterion – Burenkova (1993)

Tiago Biller - t.biller@lboro.ac.uk 6 School of Architecture, Building and Civil Engineering

Hydraulic gradient and counts of filtered AE events Amplitude ratio of signal in different frequencies

Data processing and interpretation

7

Project structure

Tiago Biller - t.biller@lboro.ac.uk 8 School of Architecture, Building and Civil Engineering

Future developments

Testing equipment

Planned apparatus improvements:

• Mechanism for varying effective stress
• Measurement of specimen deformation (LVDT)
• Mass loss quantification (sediment trap, turbidity sensor)
• Capacity to control specimen spatial orientation
• Sensor choice (Hydrophones?)

Scale modelling

Scaled mock-ups of earth dams and levees are to be used for testing phenomena like erosion progression and structural collapse in relation to AE.

Field trials

Ongoing collaboration with stakeholders gives the opportunity to apply and evaluate the knowledge from laboratory experiments in the field environment.

Tiago Biller - t.biller@lboro.ac.uk 9 School of Architecture, Building and Civil Engineering

(after Moffat and Fannin, 2011) (after Skempton and Brogan, 1994)

Equipment design

10

Inspiring Winners Since 1909

Thank you!

Tiago Biller t.biller@lboro.ac.uk

Li and Fannin, 2012 Robb et al. (2006)

Koerner et al. (1981)

flow net through idealized earth dam. Top: dam with a drainage blanket (no core) (modified after Encyclopædia Brittanica, 1999). Bottom: flow net parts: phreatic line separates saturated and unsaturated zones; blue arrows: flow direction; each field is delimited by the intersection of equipotential and flow lines.. Nd=number of potential drops; Nf=total number of flow channels (after Cedergren, 1989)

Internal instability of a soil based on its grading (H/Fmin ratio) and critical hydraulic gradients (ic), including the effect

• f

two different flow

• rientations (after Skempton and Brogan, 1994).

Modified hydromechanical envelope model by Ferdos et al. (2018). Change of in-situ principal stresses in porous media under hydraulic loading and fluid seepage; the undisturbed Mohr-Coulomb circle (black line) shifts to the left due to the hydraulic loading (blue line) and upward due to seepage flow (double blue line). τ1 and τ2 are the maximum shear stresses that the specimen can take before instability occurs, τb1 and τb2 are the total induced shear stress on the specimen and τfn is the flow-induced shear stress.

Teton Dam site at present - dam has not been rebuilt.

(ICOLD, 2014)