Overview
Compaction control of trenches has always been a difficult problem for works directions as well as for contractors. Volume of materials used is generally relatively small and this operation is thus very sort in time. Systematic controls with usual methods (volume mass, bearing capacity) are thus very difficult, expensive and disturbing for contractors.
Nevertheless, another much more interesting method exists since a few years. It's a light dynamic penetrometer, portable in a case, very easy to use in a trench, which electronic equipment allows instant results. Besides, its biggest advantage is its possible use in gravelly soils normally compacted up to 4 m thick.
The aim of this research is to attempt to correlate point dynamic resistance obtained thanks to this penetrometer to compaction control standard parameters of trenches as fixed in specifications, like volume mass and bearing capacity. Point resistance could also be suggested as new compaction control parameter and be the point of a new norm or of a modification of existing norms.
The aim of the project is to correlate results obtained thanks to new light penetrometers /lover 30 kg/, using penetration speed measure (or acceleration measure), to compaction control standard parameters, it means ME value and volumic mass; this, mainly for compaction control of trenches.
The tests were performed in trench excavations in the Geneva region by Mr. Blandin office Amsler & Bombeli. They had as initial purpose of attempting to correlate (or show that the correlations were difficult or impossible) the resistance to dynamic penetration with the parameter values currently used in Switzerland compaction control criteria. In each excavation used for the tests, the test device was used. It enabled:
• Measurement of density to a depth of about 30 cm using a Troxler nucleometre. This device measures the density (wet) ρ (gamma ray) and water content w (neutrons). It displays the density ρ of dry soil and water content. d These measures are carried out to the depths: 0-10 cm, 0-20 cm and 0-30 cm. The Troxler also allows a surface measure that has rarely been exploited.
• Measurement of the module M according to standard SN 670 317b by means of the test device described in the standard E 670 SN 312b (plate 30 cm in diameter).
• Measurement of the resistance to dynamic penetration through the PANDA penetrometer. It is important to note that these three trials could not be executed exactly the same place the bottom of the search. Moreover, as the excavation trench backfill is compacted in layers using a compacting machine acting on the surface of the layer, correlations have been established for the critical depth without surface. For the calculation of average values, however, we eliminated the random values and weak q just under the surface of 0 - 10 cm, 0-20 cm and 0-30 cm. 26 test groups (ρ, w, M, q) has been made in the excavations of the Geneva region.
Each sheet contains:
• Identification of the test
• The result of the penetration test q = f (depth) of the results of measurements
• ρ, w, M and Ed
• The size of the filling material.
Tests in 26 excavations were carried out on, virtually, a same type of materials. Proctor test standards (Ø = 16 mm grain) were performed on some of the samples collected max embankments. They were performed according to standard SN 670 320b on samples recombined after the particle sizes.
Funding
Results
Background & policy context
Compaction control of trenches has always been a difficult problem for works directions as well as for contractors. Volume of materials used is generally relatively small and this operation is thus very sort in time. Systematic controls with usual methods (volume mass, bearing capacity) are thus very difficult, expensive and disturbing for contractors.
Nevertheless, another much more interesting method exists since a few years. It's a light dynamic penetrometer, portable in a case, very easy to use in a trench, which electronic equipment allows instant results. Besides, its biggest advantage is its possible use in gravelly soils normally compacted up to 4 m thick.
The aim of this research is to attempt to correlate point dynamic resistance obtained thanks to this penetrometer to compaction control standard parameters of trenches as fixed in specifications, like volume mass and bearing capacity. Point resistance could also be suggested as new compaction control parameter and be the point of a new norm or of a modification of existing norms.
Objectives
The aim of the project is to correlate results obtained thanks to new light penetrometers /lover 30 kg/, using penetration speed measure (or accelaration measure), to compaction control standard parameters, it means ME value and volumic mass; this, mainly for compaction control of trenches.
Methodology
The tests were performed in trench excavations in the Geneva region by Mr. Blandin office Amsler & Bombeli. They had as initial purpose of attempting to correlate (or show that the correlations were difficult or impossible) the resistance to dynamic penetration with the parameter values currently used in Switzerland compaction control criteria. In each excavation used for the tests, the test device was used. It enabled:
• Measurement of density to a depth of about 30 cm using a Troxler nucleometre. This device measures the density (wet) ρ (gamma ray) and water content w (neutrons). It displays the density ρ of dry soil and water content. d These measures are carried out to the depths: 0-10 cm, 0-20 cm and 0-30 cm. The Troxler also allows a surface measure that has rarely been exploited.
• Measurement of the module M according to standard SN 670 317b by means of the test device described in the standard E 670 SN 312b (plate 30 cm in diameter).
• Measurement of the resistance to dynamic penetration through the PANDA penetrometer. It