Erwin Yan-Nam Oh

Safety evaluation for expressways: A comparative study for macroscopic and microscopic indicators

Objective: This article is to assess the performance of 3 macroscopic safety indicators (speed, speed dispersion, and volume) and two microscopic potential crash risks (time to collision and deceleration rate to avoid crash) on safety evaluation for expressways. Methods: Field data were collected at 3 locations for 4 different time periods on an expressway in Beijing, China. The speed of each vehicle, headway time, and vehicle length were recorded by a traffic management system. The 5 safety indicators were thus calibrated on the basis of the collected data. Further, consistency and comparative analyses were applied to assess the performance of indicators. Results: According to the analyses, speed dispersion was a better predictor of the two microscopic potential risks compared to the two macroscopic indicators. Conclusions: Speed dispersion is recommended to proactively assess road safety because (1) it provides consistent risk evaluation with microscopic potential risks and (2) it makes data collection easier.

Estimation of Entry Capacity for Single-Lane Modern Roundabouts: Case Study in Queensland, Australia

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.

CHARACTERISTICS OF EMBEDDED PEAT IN COASTAL ENVIRONMENTS

This study examines the engineering characteristics and properties of peat soils in coastal environments in Ireland, Italy, Malaysia, Netherlands, Turkey and USA. The engineering properties to be examined are consolidation characteristics, Atterberg limits, density, organic content, shear strength, and moisture content. Moisture content and organic content are good indication of the occurrence of peat soils because these parameters are inherently high in this soil type. In addition, peat soil is highly compressible and is known to be problematic for geotechnical construction. The peat layer has an adverse effect on the long-term settlement of road embankments. A case study of peat soil deposits in Surfers Paradise in Australia will be presented in the paper. Peat soil in the study area is embedded at depth ranging between R.L. -10 to R.L. - 19.6 m below the ground surface and it has a thickness ranging from 0.1 to 7.0 m in some locations. It possesses low shear strength of between 30-40 kPa and the moisture content can be up to 247 %. Four empirical equations have been established for the peat soils and they are compared with those published in the literatures.

Laboratory Assessment of Kaolinite and Bentonite under Chemical electrokinetic Treatment

Electrokinetic treatment uses low intensity direct electric current or a low electric potential difference, to improve the engineering properties of subsurface soils while having minimum disturbance to the surface. This study aims to investigate the effects of chemical-electrokinetic treatment on properties of two types of clay soils at different intervals under the coupled Chemical, Hydraulic and Electrical (CHE) gradient. “Chemical-electrokinetic treatment” refers to improvement of soil with electrokinetic together with addition of chemical enhancement solution. The enhancement solutions used in this study are hydrated lime and saline solution. The combined effects of these processes together with various electrochemical and geochemical reactions would change the chemical composition of the soil porous medium, hence modifies the properties of the soil. The experiments were conducted in the laboratory using stainless steel electrodes under total applied voltage of 30 V for period of 15 days. Two types of fine-grained soils, kaolinite and bentonite, were used as they possess different mineralogy and geotechnical properties. The cumulative electro-osmotic flow and electric current flow through the soil samples were measured for period of 15 treatment days. Subsequently the specimens were tested for moisture content, pH and Atterberg Limit variations and the results have been reported. Test results revealed that there is a potential of developing this technique to improve engineering properties of finegrained soils, in particular to stabilise and improve soft soils for infrastructure management and constructions.

Evaluation of Roundabout Capacity Models: An Empirical Case Study

AbstractBased 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 −...

GIS-based examination of peats and soils in Surfers Paradise, Australia

Abstract The subsoil conditions of Surfers Paradise in Southeast Queensland of Australia have been examined in terms of soil stiffness by using geographic information system (GIS). Peat is a highly organic and compressible material. Surfers Paradise (as a study area) has problematic peat layer due to its high water content, high compressibility, and low shear strength. This layer has various thicknesses at different locations ranging between R.L. . 10 to R.L. -19.6 m. Buildings in Surfers Paradise are using piled foundations to avoid the high compressibility and low shear strength peat layer. Spatial Analyst extension in the GIS ArcMap10 has been utilised to develop zonation maps for different depths in the study area. Each depth has been interpolated as a surface to create Standard Penetration Test SPT-N value GIS-based zonation maps for each depth. In addition, 8 interpolation techniques have been examined to evaluate which technique gives better representation for the Standard Penetration Test (SPT) data. Inverse Distance weighing (IDW) method in Spatial Analyst extension gives better representation for the utilised data with certain parameters. Two different cross sections have been performed in the core of the study area to determine the extent and the depth of the peat layer underneath already erected buildings. Physical and engineering properties of the Surfers Paradise peat have been obtained and showed that this peat falls within the category of tropical peat.

Static and Dynamic Load Tests of Shaft and Base Grouted Concrete Piles

This paper examines shaft and base grouted concrete piles by conducting vertical static load tests (SLTs) and dynamic load tests. Three concrete piles with shaft and base grouting, with base grouting only, and without grouting techniques were selected, and compressive SLTs were conducted. Two piles with grouting were also assessed with dynamic load tests. Another two uplift SLTs were conducted to one shaft and base grouted pile and one pile without grouting. Traditional presentations were provided to check whether the bored piles reached the design requirement. Interpretations of test results were also provided to determine the ultimate pile capacity. Results from these 5 SLT programs indicated that double-tangent and DeBeers methods are close to each other, and Chins method overestimates the pile capacity. Comparison of the results from the SLTs and dynamic load tests shows that the results from Chins method are close to dynamic results, and Mazurkiewiczs method overestimates for friction resistance. The results also demonstrate that base and shaft grouted pile and base grouted pile increase by 9.82% and 2.89% in compressive capacity, respectively, and compared to the uplift SLTs; there is a 15.7% increment in pile capacity after using base and shaft grouting technology.

MODELLING GROUND RESPONSE FOR DEEP EXCAVATION IN SOFT GROUND

Due to its simplicity in use and input parameters can be straightforwardly determined (from in-situ tests, laboratory tests and empirical correlations), linear elastic perfectly-plastic Mohr-Coulomb (MC) model remains a favourite constitutive modelling choice to Geotechnical engineers. Non-linear Hardening Soil (HS) model is an improvement of MC model. It is not commonly used mainly due to lack of appropriate non-linear drained stiffness parameters from laboratory tests and field calibrations. Using a deep excavation project as a case study, this paper presents a comparison of MC and HS models in assessing wall deflection. The numerical models are established based on soil parameters interpreted from available soil investigation. It was found from back analysis of a case history that laboratory tests and empirical correlations grossly underestimated the drained stiffness parameters. In order to close the gaps between predicted and observed deflections, the drained stiffness parameters have to be increased by six-fold and more than eight-fold for MC Model and HS Model, respectively.

Model for Benchmarking a Pavement Maintenance Budget for Sustainable Road Transport Infrastructure

Road agencies worldwide are investing billions of dollars on road maintenance. Pavement management system is often used to forecast the pavement maintenance cost and for prioritisation of the road sections for rehabilitation. This paper examines an approach for forecasting road network maintenance budget using road network condition as a basis for estimating future maintenance cost. The study establishes the relationship between the road pavement maintenance budgets with the pavement condition indices for road networks for several local government authorities in Southeast Queensland. A budget projection model will be developed using the maintenance cost and condition indices relationship. In addition, a pavement sustainability index will also be developed to demonstrate the gap in the maintenance funding. The budget projection model enables local councils to benchmark their maintenance expenditure and road network condition with other councils nationwide.

Probabilistic Capacity Modeling for Single-Lane Roundabout

The Highway Capacity Manual 2000 (HCM 2000) model estimates entry capacity of roundabouts under an assumption of headway (time gaps) following an exponential distribution. Entry capacity is thus calculated by circulating flow, critical gap and follow-up time. This paper aims to analyse: (1) the actual distribution type of headway; and (2) the relative error resulting from the assumption. To this end, a simulation that simulates the real traffic operation is conducted based on survey data from an existing roundabout in Queensland, Australia. A comparative study is then carried out to compare the results from the HCM 2000 model and the simulation. It indicated that the HCM 2000 model is not appropriate to be established under an exponential distribution. Although HCM 2000 model over-estimated capacity in our case study, it is still an acceptable approximation. Results suggest that the relative error is 6% under the circulating flow of 468 vehicles/hour.