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The effects of cement dosage (percentage by dry soil weight) and initial moisture content (wo) on cement stabilized soft estuarine clay were investigated by effective integration of multi-quantitative analyses, including quantitative X-ray diffraction (XRD), thermalgravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) test and scanning electron microscopy (SEM) with image processing. These quantitative analyses are highly complementary, which greatly improved the scientificalness of this research. The results revealed that the strength development of cement stabilized soft estuarine clay with varying cement dosages, and initial moisture content was ascribed to the combined influence of both soil fabric improvement and cementation bonding enhancement. The increase of wo resulted in larger clay particle spaces, which can counteract the enhancement of soil structure due to the rising hydration products. The hydration degrees of samples with fixed cement dosage but different wo are quite similar, while clay particle spaces were enlarged with an increase of initial moisture content. Thus, the same quantity of hydration products may bind more soil particles when pores are small at lower wo , thus increasing unconfined compressive strength (UCS). Furthermore, BET and quantitative SEM results illustrate that hydration degree plays a dominant role in the development of intra-aggregate pores (<0.2 μm), while wo affects inter-aggregate pores (0.2 μm–2 μm) more. Construction of buildings and infrastructure on marginal ground is becoming more common due to rapid urbanization and population growth. These phenomena has led to the utilization and development of coastal and estuarine plains surrounded by relatively softer and weaker soils that require improvement or strengthening before being constructed upon. One such ground improvement method is termed deep soil mixing (DSM), which involves mixing cement with the in situ weak soils to increase the soil strength so that the ground can sustain the weight of the buildings or infrastructure. This manuscript presents a novel interpretation based on the results from advanced laboratory tests to succinctly explain the complex chemical reactions that occur when cement is mixed with soft soils having varying characteristics. It is envisaged that this evidence-based explanation will help engineers and scientists bring to life land that was previously deemed unsuitable for construction. [ABSTRACT FROM AUTHOR]

Based on field data collected at nine roundabouts in Gold Coast, Australia, this paper evaluates the performance of the capacity estimation for single-lane roundabouts using analytical models [including the highway capacity manual (HCM) 2000 model, the German Highway Capacity Manual (GHCM) model, the signalized and unsignalized intersection design and research aid (SIDRA) model and a new roundabout capacity (NRC) model] and an empirical model (the HCM 2010 model). First, this study calibrates critical gaps, follow-up times, and conflicting flows. Compared with the capacities measured in the field, the authors carry out a study to analyze the accuracy of the HCM, GHCM, SIDRA, and NRC models. The results show that the five models underestimate capacity but the NRC model produces a smaller range of relative error (−1.07 to −5.74%) and root-mean-square deviation (47.68) than the HCM 2010 (−4.62 to −16.14% and 105.00, respectively), HCM 2000 (−5.76 to −17.21% and 115.29, respectively), GHCM (−8.95 to −21.26% and 146.82, respectively), and SIDRA (−5.15 to −17.51% and 113.48, respectively) models. Accordingly, the NRC outperforms the other four models for the surveyed roundabouts. The five models estimate a similar capacity in low and medium traffic volumes, and exiting vehicles play an important role in high traffic volumes, and at high traffic condition exiting vehicles warrant more entry opportunities that exceeds the impact of high circulating volumes on entry capacity. [ABSTRACT FROM AUTHOR]

Single-lane modern roundabouts are one of the most important intersection types in the suburbs of Australia. Therefore, it is important to estimate their entry capacities. In this case study, an analytical model based on the gap acceptance theory by incorporating the effects of the exiting vehicles is proposed. Then, a scenario analysis is carried out to assess the effects of the exiting indicators. This is followed by the discussion of the applicability of the proposed model. The results show that the transport authorities need to strictly enforce the use of indicators before exiting in order to achieve higher capacity. [ABSTRACT FROM AUTHOR]