Analysis of field performance—the Thunder Bay tunnel

1986 ◽  
Vol 23 (1) ◽  
pp. 30-50 ◽  
Author(s):  
Robert M. C. Ng ◽  
K. Y. Lo ◽  
R. K. Rowe
Keyword(s):  
Field Performance ◽  
Field Measurements ◽  
Pressure Change ◽  
Long Term Conditions ◽  
Perfectly Plastic ◽  
Thunder Bay ◽  
Short And Long Term ◽  
Elastic Perfectly Plastic ◽  
Spatial Displacements

A numerical method for the calculation of the distribution of displacements for tunnelling in clays has been developed. The method employs an orthotropic elastic – perfectly plastic soil model that takes into account various sources of ground loss and soil–lining interaction. Both undrained and drained analyses have been carried out and the results are compared with the measured soil displacements of two instrumented arrays at the Thunder Bay tunnel. It is shown that the range of maximum settlements, the shape of the settlement troughs, and the pore pressure change, as well as the magnitude and direction of spatial displacements obtained from the analyses, compare reasonably well with the results of field measurements for both short- and long-term conditions. Key words: tunnelling, clays, anisotropy, elastic–plastic displacements, settlement trough, Thunder Bay tunnel.

Predicted and measured stresses and displacements around the Darlington Intake Tunnel

1984 ◽  
Vol 21 (1) ◽  
pp. 147-165 ◽  
Author(s):  
K. Y. Lo ◽  
B. Lukajic
Keyword(s):  
Field Measurements ◽  
Time Dependent ◽  
Long Term Conditions ◽  
Field Instrumentation ◽  
Deformation Properties ◽  
Strength And Deformation ◽  
Short And Long Term ◽  
Keywords Stress

The C.W. Intake Tunnel of the Darlington Nuclear Station is D-shaped in section with a span of 8 m and a length of 925 m beneath Lake Ontario. The tunnel is located in a horizontally bedded limestone with variable shaly interbeds.The geotechnical investigation including in-situ rock stress measurements, and laboratory determination of strength and deformation properties as well as time-dependent behaviour are reported. Design of the tunnel, in particular provisions for "rock squeeze," is described in detail.To verify the design approach adopted and the provisions made, field instrumentation was performed during excavation of the tunnel. The results of field measurements of stresses and displacements were compared with premonitoring analysis. Postmonitoring analyses were also performed using the as-constructed condition. It is shown that the performance of the tunnel is in general agreement with the predicted behaviour in both short and long term conditions. Keywords: stress, displacement, time-dependent deformation, stressmeter, tunnel, rock mechanics, rock squeeze.

scholarly journals Predicted and measured time-dependent behavior of highway embankment on cohesive soil stratum

2021 ◽  
Author(s):  
Juraj Chalmovský ◽  
Miča Lumír
Keyword(s):  
Constitutive Model ◽  
Constitutive Models ◽  
Cohesive Soil ◽  
Long Term Conditions ◽  
Perfectly Plastic ◽  
Pore Pressures ◽  
Stress Dependent ◽  
Excess Pore Pressures ◽  
Excess Pore

Highway embankments are important structural elements in modern road infrastructure. If such a construction is built on cohesive low-permeability soils, it is necessary to perform a prediction of long-term settlements and excess pore pressures. The paper presents a numerical analysis of an instrumented embankment constructed in the Czech Republic using the finite element method. Two alternative constitutive models were employed throughout the analysis: standardly used linear elastic perfectly plastic model and elastoplastic model with volumetric and shear hardening with stress-dependent stiffness. A construction sequence was modelled in detail including durations of partial construction stages. Both the settlements of subsoil (in short-term and long-term conditions) and excess pore pressures measured in multiple depths were evaluated and compared with predictions. Results employing a more complex constitutive model show a reasonably good agreement with measurement both in terms of settlements and pore pressures. The application of a perfectly plastic constitutive model leads to an overestimation of settlements.

The Interface Behavior between External FRP Reinforcement and Masonry

2014 ◽  
Vol 624 ◽  
pp. 178-185 ◽  
Author(s):  
Marianovella Leone ◽  
Margherita Stefania Sciolti ◽  
Francesco Micelli ◽  
Maria Antonietta Aiello
Keyword(s):  
Mechanical Performance ◽  
Fiber Reinforced ◽  
Long Term Conditions ◽  
Existing Structures ◽  
Bond Performance ◽  
Reinforced Composite ◽  
Fiber Reinforced Polymer Composites ◽  
Frp Reinforcement ◽  
Short And Long Term

The need to guarantee higher safety levels of masonry structures under both short and long term conditions, have led to the use of new materials and technologies, in conjunction or in place of traditional ones. In this context, fiber-reinforced composite materials have gained an increasing success, mostly for strengthening, retrofitting and repair existing structures. As well known, the analysis of the interface performance of FRP (Fiber Reinforced Polymer) composites and masonry substrate is a critical problem as it influences the effectiveness of the technique. The present paper reports part of a large research project, still in progress, focused on the analysis of the bond performance between FRP sheet and different type of masonry substrates. The obtained experimental data were analysed in terms of bond strength and the kind of failure. The influence of the deformability of the strengthening material as well as the mechanical performance of the substrates are also discussed.

Holding capacity of dynamically installed anchors in normally consolidated clay under inclined loading

2017 ◽  
Vol 54 (9) ◽  
pp. 1257-1271 ◽  
Author(s):  
Yong Fu ◽  
Xiying Zhang ◽  
Yuping Li ◽  
Hai Gu ◽  
Jie Sun ◽  
...  
Keyword(s):  
Failure Modes ◽  
Soft Clay ◽  
Variable Cross Section ◽  
American Petroleum Institute ◽  
Centrifuge Model Test ◽  
Variable Cross ◽  
Long Term Conditions ◽  
Lateral Resistance ◽  
Short And Long Term

This paper describes a design framework for inclined tensile loading capacity (holding capacity) of dynamically installed anchors in soft clay. Centrifuge model test and numerical results indicate that, while ultimate inclined holding capacity increases with a loading angle smaller than 45° (to the vertical at anchor padeye), anchor failure is controlled predominantly by the ultimate vertical holding capacity, which can be predicted using the American Petroleum Institute method put forth in 2007 with interface friction ratio of 0.25–0.34 and 0.60–0.82 for short- and long-term conditions, respectively. For a loading angle larger than about 65°, anchor failure is controlled largely by the ultimate horizontal holding capacity. It is proposed herein that the ultimate lateral holding capacity can be estimated by generalizing Broms’ method put forth in 1964 for lateral anchor capacity to variable cross section; thereby allowing anchor geometry to be considered in a rational manner. Good agreement can be obtained between the estimated ultimate horizontal holding capacity and that computed using the finite element method by using a lateral resistance of 10.5su, where su is the undrained shear strength. For a loading angle between 45° and 65°, there is significant interaction between vertical and horizontal failure modes. This allows a normalized horizontal–vertical interaction curve to be defined by fitting data from this and previous studies.

Short- and Long-Term Results of Total vs Subtotal Thyroid- ectomies in the Surgical Treatment of Graves' Disease

Swiss Surgery ◽  
2001 ◽  
Vol 7 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Robert ◽  
Mariéthoz ◽  
Pache ◽  
Bertin ◽  
Caulfield ◽  
...  
Keyword(s):  
Recurrent Laryngeal Nerve ◽  
Nerve Palsy ◽  
Recurrent Laryngeal Nerve Palsy ◽  
Laryngeal Nerve ◽  
Long Term Results ◽  
Graves Disease ◽  
Laryngeal Nerve Palsy ◽  
Short And Long Term

Objective: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. Methods: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue - mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. Results: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT - with follow-ups averaging two years (0.5-8) - are receiving thyroxin substitution. Conclusions: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

Short- and long-term memory tasks predict working memory performance, and vice versa.

2019 ◽  
Vol 73 (2) ◽  
pp. 79-93 ◽  
Author(s):  
Ian Neath ◽  
Jean Saint-Aubin ◽  
Tamra J. Bireta ◽  
Andrew J. Gabel ◽  
Chelsea G. Hudson ◽  
...  
Keyword(s):  
Working Memory ◽  
Memory Performance ◽  
Long Term Memory ◽  
Term Memory ◽  
Short And Long Term
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