Almost all of the existing testing methods to determine elastic modulus of the soil or aggregate for pavement design involve the application of repetitive loads applied at a single point. This approach falls short of representing the conditions that are observed when the wheel of a vehicle rolls over the surface. This study presents a new methodology, in which light weight deflectometer (LWD) is used to apply three adjacent sequential loads repetitively to replicate a multipoint loading of the surface. The elastic modulus values obtained from these multipoint LWD tests were compared against the repetitive single point LWD test results. The multipoint LWD test elastic modulus values were consistently lower than the values obtained from the single point LWD tests. The single point LWD tests showed an increase in elastic modulus with increased load repetition. The multipoint LWD results did not show an increase in the elastic modulus as a function of repetitive loading. This study showed that damping ratio values provide guidance to explain differences in the elastic modulus with an increased number of load repetitions. In repetitive single point tests, the applied load caused initial compaction, and in multipoint LWD tests, it caused disturbance in the ground. With increased load cycles, the ground reached a stabilized condition in both tests. The methodology presented in this study appeared to minimize the unintended compaction of the ground during the single point LWD tests to determine the elastic modulus.

Loess is a geological formation with poor geotechnical performances. To upgrade and allow use of this kind of material in civil engineering projects, it is common to add few percent of hydraulic binders. However, the mechanical properties of those materials are often estimated. Their performances are thus sharply downgraded during structure design processes of road structures and their uses are generally limited to the capping layer. However, it is possible to measure accurately mechanical performances of these materials to use them in subbase layers of pavements. Based on results, a design has been proposed and implemented on a real scale test section. The test has been instrumented with strain gauges and preliminary results are presented.

Cement stabilization of soils is a common technique to enhance engineering and mechanical properties of in situ soils in the field of road geotechnics. Usually, moderate quantities of cement are used, around 5-10% of the dry material. However, cement manufacturing is one of the biggest sources of greenhouse gas emissions, specifically carbon dioxide. For this reason, reducing cement content by a few percent in geotechnical structures made with cement-stabilized soils (CSS) has a high environmental interest, particularly in view of the involved volumes of material. This work aims to contribute to a better understanding of the mechanical characteristics of lightly stabilized soils. First, the mechanical behavior of a clayey and a sandy soil treated with 3% cement was studied for several curing times. Next, measured mechanical features were correlated. Finally, these measurements were used to characterize the Mohr-Coulomb failure criterion and compared with a conventional approach. Results point out that mechanical enhancement can be quantified in terms of cohesion. Friction angle seems to be independent of curing time. The proposed approach can be adapted in geotechnical applications based on the Mohr-Coulomb yielding criterion such as stability slopes, foundations, and retaining structures.

Biochar is an eco-friendly material that is potentially used in earthworks to prevent stability and serviceability problems under extreme scenarios. This study aims to examine the effects of biochar amended on water infiltration and evaporation under extreme climate. A series of numerical analyzes were conducted to observe the response of pore water pressure (PWP) to extreme climate variation with an application of biochar composition. Moreover, an analysis of variance (ANOVA) has been performed to investigate the effect of biochar on soil water holding capacity at a low suction range. According to the result, biochar amended can maintain the fluctuation of PWP due to wetting and drying processes under extreme climate scenarios. This is due to the fact that the finer particles of biochar may clog large soil pores, reducing the water infiltration rate. Moreover, the addition of biochar can increase water retention capacity at low matric suction ranges, which can prevent flooding during extreme wet conditions. Further to this, the addition of biochar to the soil can maintain PWP fluctuation at the near surface area under extreme climate, preventing soil desiccation cracks.

Examples of upscaling phenomena with experimental techniques are presented and discussed within the framework of compacted soils for hydraulic and environmental earthworks and engineered barriers for the energy sector. A series of laboratory experiments at different scales are presented and interpreted to focus on the need for experimental upscaling in compacted soils since distinctive behavioural features can only be detected at specific length scales. Permeability results on fine-grained soils and artificially prepared sand/bentonite mixture at different scales will be discussed with microstructural tests regarding 'dry' or 'wet side' compaction, element and mock-up tests on compacted soils in the laboratory, and field tests on a compacted trial embankment and demonstration test to explore anisotropic and heterogeneous features. The presented examples will help to motivate new experimental research subjects and promote experimental protocols at different scales ranging from mm-scale (micro), cm-scale element tests, dm-scale mock-ups and m-scale (trial/demonstration tests) to help understand and approach some fundamental questions observed at the application scale of compacted soils.