Toan Trinh

In civil engineering, the study of embankment settlement on soft ground is a vital geotechnical task in order to maintain serviceability of the road embankment, pavement, and facilities. This paper presents a study on settlements of road embankment on soft ground using vertical drains, including prefabricated-vertical drain (PVD), sand drain (SD), and sand compaction pile (SCP) on a number of packages of Hanoi – Haiphong Expressway Construction Project. The effectiveness of settlement prediction of vertical drain solutions is evaluated considering the ratios between the observed consolidation settlements and settlements predicted in the Detailed Design, in relation to the thickness of soft soil and the depth of treatment. Regression analysis is used to establish the correlation between the observed settlement and the height of embankment. The results show that (i) the design generally overestimated settlements; (ii) the ratios between observed and predicted settlements tend to positively correlate with the thickness of soft soil and the depth of treatment, and (iii) there are positive correlations between the height of embankment and the observed settlement. These correlations can be a valuable source of reference for anticipating settlements in basic design of highway projects with soft ground treated by vertical drains, in the regions that have geological stratum similar to Thabinh and Haihung formations of Bacbo Plain

Almost every year, Vietnam suffers floods resulting in the loss of many lives and considerable costs for damaged and lost properties. This study proposes a forecasting system that couples the dynamical downscaling technique with hydrologic models to forecast real-time flood events with a lead time ranging from one to three days. This approach is demonstrated by applying a regional numerical weather prediction and physically based hydrologic model to the Thanh My and Nong Son watersheds. System inputs are provided by two global NWPs, the global forecasting system (GFS) and the global spectral model (GSM). A WEHY-WRF was selected as the hydrologic-atmospheric component for the proposed system. WEHY-WRF was successfully implemented and validated before testing the real-time forecasting system over the Nong Son-Thanh My watersheds. Overall, the comparison between the model simulations and corresponding observations shows the rainfall and flood forecast by WEHY-WRF-GFS match quite well with observation data and perform better than WEHY-WRF-GSM. However, all forecasting results are generally encouraging considering the correlation coefficients for most events are acceptable. The forecast methodology has demonstrated it as a comprehensive reliable technology that may be universally applied for flood prediction through the coupling of dynamical downscaling technique and hydrologic models.

Tạp chí Khoa học Giao thông vận tải - Trường Đại học Giao thông vận tải;Transport and Communications Science Journal under University of Transport and Communications was established in 2002 and launched online version in 2019.

Hydrologic modeling can contribute to quantify the relation between precipitation and stream discharges. Most of hydrologic models have various m |

Traffic control decisions for incident congestion management on expressways are often made in the face of uncertainty because it entails using many forms of both current and predicted traffic data and incident information to arrive at control decisions under critical-time pressure. For these reasons, an effective traffic control strategy during incidents often relies on techniques that deal efficiently with problems of uncertainty and imprecision. Motivated by this, the author has carried out a research project that develops a multi-stage Fuzzy Logic Controller (MS-FLC) as a tool to support traffic operator’s decision-making at the operational level. The research project aims at establishing a systematic procedure in deriving control actions for ramp control during incidents on expressways following fuzzy-logic approach. For proactive ramp control, the trend of traffic condition on expressways during incidents should be properly anticipated. This paper presents the first two stages of the MS-FLC: (1) evaluation of traffic condition upon incident occurrences, and (2) anticipation of traffic condition during incidents. The results show that the MS-FLC provides a systematic procedure in deriving control actions using fuzzy-based methodology, which possesses excellent capabilities in data-handling and knowledge representation to deliver linguistic expressions that is easy to understand by the operators for making decisions. With both current and anticipated types of information obtained from these two stages, the MS-FLC operates on both reactive and proactive control manners so as to enhance performance of the incident management on expressways.

Estimation of probable maximum flood (PMF) is a crucial process in water resources management and in the design of large hydraulic structures. However, there are uncertainties in the estimation of hydrologic conditions that contribute to extreme floods. In particular, this is the case in snow‐dominated regions, as surface air temperature and wind speed are understood to have a substantial effect on the magnitude of a flood during a storm event. Motivated by the development of a new approach to investigate and estimate reliable PMF values and in an attempt to resolve the uncertainty issues, this study introduces a physically based modeling approach. For the case study, seven watersheds located in the Sierra‐Nevada mountain range of California, including Cosumnes, Mokelumne, Stanislaus, Tuolumne, Merced, Upper San Joaquin, and Upper Kings were selected. The hydroclimate model was first implemented over the physical boundaries of the study region, and then utilized to simulate possible maximum flood conditions with input from 10 extreme precipitation scenarios. The study results provide evidence of a nonlinear atmospheric–hydrologic system; the extreme 72‐h basin‐averaged precipitation depth was found not to be linearly proportional to 72‐h flow volume equivalent depth. It can also be concluded that a large precipitation depth may not be the sole reason for a large flood event. Temperature and other atmospheric variables also contribute significantly to the production of snowfall and liquid water available for runoff, and to the resulting hydrologic response, such as the flood peak discharge and volume.

Rủi ro kỹ thuật là một dạng rủi ro phổ biến nhất trong các dự án đầu tư xây dựng công trình giao thông. Do vậy, chúng cần được nhận dạng và phân loại sớm nhằm hỗ trợ việc ra quyết định đầu tư trong giai đoạn lập dự án. Bài báo này giới thiệu kết quả nghiên cứu việc nhận dạng các rủi ro kỹ thuật điển hình trong các dự án đường bộ sử dụng cấu trúc các hạng mục công việc xây lắp, và phân loại các rủi ro theo cấp rủi ro, áp dụng nhận dạng và phân loại các rủi ro kỹ thuật của dự án đường cao tốc Hà Nội – Hải Phòng. Kết quả nghiên cứu cho thấy việc nhận dạng rủi ro sử dụng cấu trúc các hạng mục công việc cho phép rà soát một cách toàn diện và hệ thống các rủi ro kỹ thuật của dự án, và việc phân loại rủi ro theo cấp độ cho phép sắp xếp các rủi ro một cách có cấu trúc, tường minh, giảm thiểu sự chồng chéo hay bỏ sót rủi ro, đặc biệt thích hợp cho những dự án lớn.

This study investigates the effect of variability of layer thickness and elastic modulus of pavement materials on the reliability of flexible pavement structural performance with respect to rutting failure using the mechanistic design approach. Monte Carlo simulation was applied to incorporate the variability of input design parameters in establishing the probability distribution of reliability of multi-layered flexible pavements. Using Matlab 7.0 programming language, a programme named DTC1.0 was developed for calculating the overall elastic modulus and pavement reliability. Data from some National Highways of Vietnam were used to construct statistical distributions of layer thicknesses and elastic moduli. Sensitivity analyses were conducted to identify key input parameters that have the most effect on reliability. The research shows that changing the value of the coefficient of variation (COV) affects the reliability of the flexible pavement at different levels: the higher the COV, the higher the rate of decrease in the reliability. Changes in thickness and elastic modulus of upper layers have more impact on reliability than lower layers. The influence of COVs of the elastic modulus is larger than that of the thickness. It is expected that the study can provide the foundation to develop a reliability-based design procedure following the mechanistic design approach.