The use of light weight deflectometer for in situ evaluation of sand degree of compaction

Abstract

The light weight deflectometer (LWD), also known as the light falling weight deflectometer, light drop weight tester, and dynamic plate load test, is a hand portable device that was developed in Germany to measure the soil in situ LWD dynamic modulus. Typically, this modulus is used to evaluate the subsoil degree of compaction. Thus it is suitable for compaction quality control of soil-surfaced roads, embankments and replacement fill. As a dynamic test, the device is suited, in particular, for coarse and mixed grained soils with a maximum grain size of 63 mm. The response of poorly graded calcareous and siliceous sands is the focus of this research. First, the index soil properties of the tested soils including grain size distribution; maximum and minimum void ratios and specific gravity were obtained. Petrographic analyses of the tested sands were also performed to determine their mineralogical composition. A 1-m 3 chamber was built for performing the LWD testing in the laboratory. The study was performed for relative densities of 20%, 40%, 60% and 80% to represent the behavior of very loose, loose, medium dense and dense sands. The effect of the existence of a rigid boundary beneath the tested soil on test results was also investigated to determine the zone of influence of the light weight deflectometer.

Compaction Quality Monitoring of Open-Graded Aggregates by Light Weight Deflectometer and Soil Stiffness Gauge

“…Examples of the target values are shown in Table 1. Elhakim et al [16] built a 1 m 3 soil chamber and obtained relationships between the RC and E LWD of two poorly-graded sand, and compared the test results with the suggested values of the German Federal Ministry of Transport [17]. This study found that the average of the E LWD -RC relationships evaluated in the two sand was similar to the suggested values [17], and the results were better agreed with the suggested values [17] when the RC was greater 95%.…”

“…After the compacted sample was prepared, two SSG and four LWD tests were conducted (Figure 6c) in a row to evaluate the stiffness. When conducting the tests, the test area should be 1.5 times larger than the diameter of the loading plate (30 cm) [16,34]. Accordingly, the test points were placed symmetrically as shown in Figure 7 from the center of the chamber, and the effort was made to perform the test at least 15 cm away from the wall of the chamber to secure the test area and to avoid wall effect.…”

“…This method, which is called modulus-based QC, is gaining popularity with the adoption of the mechanistic-empirical pavement design (MEPDG) method, and its advantage is that the measured modulus is directly related to the structural performance of the pavement and its design parameters [14]. Correspondingly, many studies have been conducted, and related specifications have been established [8,[15][16][17][18][19][20]. In particular, Nazarian et al [21] conducted extensive laboratory, small-scale, and field tests with various unbound road base materials and proposed modulus-based compaction specifications for estimating target modulus and for field quality control; Walubita et al [22] established a comprehensive data storage system for better calibration of the mechanical-empirical design and rehabilitation of flexible pavements.…”

Quality Assessment of Road Pavement using Lightweight Deflectometer

“…A study conducted by Elhakim et al [10] is to investigate the seismic waves propagated by Lightweight deflectometer (LWD) test on clay, silt and gravel soils. It showed that the usable frequency ranges from 10-300 Hz for surface waves, which can be used for low strain modulus characterization at the top 0,3-0,5 m thick soil layer.…”

Avaliação do potencial de uso do deflectômetro de impacto leve para medidas de deflexão em pavimentos urbanos

“…Assim surgiu o equipamento De lectômetro de Impacto Leve ou o Light Falling Weight De lectometer (LFWD). O LFWD é um equipamento portátil, desenvolvido na Alemanha no inıćio dos anos 80, que avalia materiais pela sua deformação, quando submetidos a uma carga dinâmica (Elhakim et al, 2014). O LFWD, assim como a VB, é utilizado para controle de qualidade das camadas do pavimento (subleito, sub-base e base), em pavimentos novos ou em obras já existentes (Nazaal, 2003).…”