A new downhole measurement technique has been proposed based on optical fiber Bragg grating (FBG) sensors for long-term monitoring of strain and its corresponding stress build-up in geological fault zones. Design and development of the present downhole sensor installation equipment have been demonstrated. Results from laboratory tests and from first field experiments in a research borehole at Trizonia island in the Gulf of Corinth area (Greece) have been reported.
A fiber Bragg grating (FBG) sensor network has been installed into a large diameter concrete pile on a real construction site. The intention was to monitor its deformation behavior during several quasi-static loading cycles. The skin friction between pile and subsoil affecting the ultimate bearing capacity of the pile as well as the settlement behavior of the structure under investigation has been derived from our measurements. A comparison between the results of the fiber Bragg grating sensors and conventional concrete strain gages (CSG) has shown excellent correspondence.
In recent years fiber Bragg gratings have been successfully introduced as sensors for strain, temperature and pressure variations. Their performance and reliability has been proven in many practical applications including strain monitoring in civil engineering and tunneling, downhole monitoring in oil reservoirs and flow assurance monitoring in pipelines. The gratings have great potential to at as true structurally integrated sensor elements. They can be embedded in typical structural or reinforcing elements of civil and geotechnical buildings. Several methods of interrogation schemes are established depending on the desired accuracy and resolution of the measurement. The most important methods are the linear discriminator, the tunable Fbry-Perot filter technique, and several interferometer setups.
A theoretical concept and its experimental realization of a fiber-optic Bragg grating strain sensor system to measure dynamic deformations in rock masses are presented. The system has been designed in order to monitor strain variations in the range of 10-9 within a bandwidth of 0.1 to 2 kHz. First promising results from field experiments are shown where seismic signals have been detected, in comparison with conventional geophone registrations.
We report on a new type of optical extensometer for strain measurement in geotechnical and civil engineering applications. The system key elements are Fiber Bragg Gratings (FBG) embedded in glassfiber reinforced polymer (GRP) rockbolts. In order to monitor rock deformations in tunnels, a prototype sensor rockbolt was designed. First measurements have been made to demonstrate the characteristics of the sensor system.
We study the evolution of solitary waves in inhomogeneous nonlinear arrays of waveguides. We use both a continuous and a discrete approach. For the continuous approximation we find a Lagrangean that permits to change to a set of ordinary differential equations. The evolution of the solitary waves is studied for various inhomogeneous arrays.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.