Evaluation of the possible use of a light falling weight device for compaction control of unbound subbase layers (VSS2002/501)
Overview
Background & policy context:
The new standard across the board test ME (Standard SN 670 317b) has eliminated certain shortcomings of the previous experimental procedure, but were at the same time the time required for testing, and thus their costs significantly increased. The practice of installation check the road with a systematic application of quality management attracts a corresponding inspection efforts. Both factors contribute to increase the control effort.
The aim of this project is to look for ways which can reduce significantly the amount of time and costs without sacrificing quality control activities. The purpose of the examination of the applicability of the light falling weight was offered by some manufacturers in Germany and Denmark. The Light Drop-Weight Tester is fast and simplified (no counterweight needed). Experimental procedure allows the implementation of a dense network of checkpoints with minimal effort and provides an ideal control tool for small construction sites (grave fills, foundation backfilling, etc.).
Objectives:
The scope of this research project is to investigate the possibilities to carry out compaction controls of unbound layers with a much lesser use of time and cost resources in comparison to the standardized plate loading test ME (SN 670 317b) while maintaining the current quality levels.
The research deals in particular with the application of a light falling weight device being manufactured, partially with minor differences in construction and accessories, by a number of suppliers in Germany and Denmark.
Methodology:
Conducting comparative measurements between the load plate test ME and the drop weight test the extent of 6 case weight loads per ME-test on unbound foundation layers at about 100 sites. In 25% of cases of ME-trial comes with a second load on the application and there are there also the specific gravities of the foundation layers identified with the nuclear device.
The totality of the results will be evaluated with the aim of determining a practically applicable correlation, or for the determination of those conditions of application, where the application of small falling weight seems less indicated.
A total of 290 sets of measurement data on sub-base layers from the years 1966 until 2007 have been available for the research project. Of these data, the results of 49 measurement sites have been discarded for various reasons, leaving a total of 241 data sets fort the analysis. The research project was limited to the testing of unbound sub-base layers, which represents the most common application of the plate loading test. The layout of the measurement points was chosen in order to obtain a good comparability of results.
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