DSM saves the dam

DSM saves the dam

SURFACE STRUCTURESDAMS with the AASHTO guide as well as mechanistic pavementdesign procedures. A refinement of the AASHTO procedure for selection of r...

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SURFACE STRUCTURESDAMS with the AASHTO guide as well as mechanistic pavementdesign procedures. A refinement of the AASHTO procedure for selection of resilient modulus of granular base and subbase materials is also presented. (from Author)

& EMBANKMENTS

955265 Prediction of pile capacity from stress-wave measurements: a neural network approach Y. K. Chow, W. T. Chan, L. F. Liu & S. L. Lee, International Journal for Numerical & Analytical in Geomechanics, 19(2), 1995, pp 107-126.

955262 Comparison of nuclear and core pavement density measurements S. R. Sanders, D. Rath & F. Parker Jr, Journal of Transportation 966.

Engineering - ASCE,

120(6), 1994, pp 953-

This study evaluates the use of the nuclear gauge as a prospective quality-control tool by comparing nuclear-gauge performance with core density measurements. Density measurements were recorded using both core and nuclear-gauge methods on four paving projects, a statistical analyses conducted to compare the results. The analyses indicate that there is no statistical difference between the testers or in the variability of the measurements obtained with the two methods. However, the means of the measurements obtained by the different methods are statistically different and density variability depends on type of mix. A multiple-regression model is developed that correlates core density with nuclear gauge readings and type of pavement. (Authors)

955263 A mechanistic evaluation of modified asphalt paving mixtures N. Ah, S. Zahran, J. Trogdon & A. Bergan, Canadian Journal of Civil Engineering, 21(6), 1994, pp 954-965. The main purpose of this study was to facilitate decisions concerning the effectiveness of modifiers in mitigating pavement distress and improving long-term overall pavement performance in actual field conditions. Utilizing shortterm laboratory results and a mathematical prediction model, the modifiers investigated were carbon black, neoprene latex and polymer modified asphalt. The statistical general linear model and the Fisher least significant difference were used for data analysis. Results indicate that the effect of the modifier on the paving mixture properties was insignificant at low temperatures (down to -17”C), but significant at high temperatures (up to 60°C). The VESYS IIIA pavement performance prediction model was utilized to assess the effects, if any, of the modifier on the pavement’s overall performance. All the modifiers improve, to some degree, the overall pavement performance. (Authors)

Foundations

955264 The axial capacity of pile sockets in rocks and bard soils J. P. Seidel & C. M. Haberfield, Ground Engineering, 28(2), 1995, pp 33-38. In this paper, the traditional approaches to design of piles in soil and rock is briefly reviewed. It is shown that the unrelated empirical relationships developed for soil and rock lead to considerable uncertainty in the design of piles in the large class of hard soil or soft rock that are sometimes referred to as intermediate materials. A new method for predicting the shaft resistance of piles socketed into rock, is outlined. It is shown that the shaft resistance predictions of this method agree well with the field test data for rock and hard soil. It is demonstrated that shaft roughness and socket diameter are critical factors in the performance of piles constructed in these materials. (from Authors)

235A

Methods

A neural network approach for the prediction of pile bearing capacity by the stress-wave matching technique is presented. The main advantage of this approach over the traditional manual or automated matching approach is that it avoids the time-consuming process of iterative adjustment. This makes it feasible to determine the static pile capacity in real time in the field. Another benefit of this approach is that as more case histories become available, the neural network can be improved by learning from these new examples. A threelayer back-propagation network is set up to illustrate the capability of the proposed approach for 70 dynamically tested concrete bored piles. A wave equation model developed at the National University of Singapore is used to formulate the problem. The results exhibit good stress-wave matching qualities compared to those obtained by manual fitting. The pile bearing capacities agree very closely. The load-settlement curve and axial load distribution in the pile are in good agreement with the field measurements obtained from a maintained load test. (from Authors) 955266 Short aggregate piers defeat poor soils E. C. Lawton, N. S. Fox & R. L. Handy, Civil Engineering ASCE, 64(12), 1994, pp 52-55. Describes the construction, characteristics, settlement prediction, and wide ranging application of short aggregate piers, or geopiers. Traditional applications are in soil bearing capacity improvements. Applications in seismic areas, small and large building foundations, and in preventing wind uplift in a aircraft hangar are detailed. (J.M.McLaughlin)

Dams and embankments 955267 DSM saves the dam A. D. Walker, Civil Engineering - ASCE, 64(12), 1994, pp 48-51. Describes upgrading works conducted on the 21m high, 1950m long hydraulic till Lockington flood control dam in the USA. A deep-soil-mix soil-cement cut-off wall was constructed to extend the clay core and prevent seepage through the gravel/sand shell at probable maximum flood. Design considerations, construction, and quality control are detailed. The deep-soil-mix technique and other applications are outlined. (J.M.McLaughlin) 955268 The Narmada nettle grows P. Reynolds, International Water Power & Dam Construction, 47(l), 1995, pp 26-27. Construction progress and controversy surrounding the Sardar Sarover 163 m high concrete gravity dam on the Narmada River in India is described. There is state, national and international debate over the social and environmental problems caused by the reservoir. There are calls to limit the planned height of the dam. (J.M.McLaughlin) 955269 Change here for Embankment P. Wheeler, Ground Engineering, 28(2), 1995, pp 16-17. London Underground is expected to provide a 21st century transport service using infrastructure that is largely Victorian.