Papers by Keyword: Dredging

Abstract: River-carried solids, especially during floods, lead to dam sedimentation. Dredging extends dam life, but excess unusable sediment storage threatens the environment. The aim of this work is to investigate the influence of the recovery of calcined mud from Chorfa dam on the physico-mechanical and chemical characteristics of mortars fiber bundles. The sludge is used as a partial substitute for cement by volume at rates of 10%, 15%, 20% and 25%. All test specimens had water / binder (W/B) ratio and steel fibers ratio. Testing programme included measuring the fluidity, ultrasonic pulse velocity test, dynamic modulus of elasticity, flexural and compressive strengths. Compared to the control mortar, the fluidity represented by the diameter of M0, M15 and M25 mixtures decreased by approximately 11%, 14% and 22%, respectively. The compressive strength of M15 increased by 17.4% at 28 days, compared with the control specimen. At 7 days, the ultrasonic speed of the M25 mixture decreases by 1.7% compared to that of M15. The dynamic modulus of elasticity of M20 and M25 increases by 13% and 12% as the age ranges from 2 to 28 days. At 28 days, the flexural strength of the M20 blends increased by approximately 64%.

Abstract: This paper employed the water quality monitoring data of Nanfei River to analyze the water pollution status, and to contrast the water quality change of the river section which has been dredged. We selected TN, TP, COD and NH₃-N as the evaluation factors to study the spatial distribution. Results showed that TN concentration was seriously higher than the upper limit of surface water standard class V, and TP and COD values were in class V, and NH₃-N concentration was in class III. Refer to previous water quality monitoring data, dredging projects of Nanfei River worked significantly on TP, COD and NH₃-N removal, while TN concentration was 5 times more than before.

Abstract: Cutter suction dredgers perform a major part in the field of dredging engineering in harbors, fairways, and land reclamation. However, there are many parameters in cutter suction dredger operation so that it is difficult to guarantee the stability of production. In consideration of the issue of enormous parameters in dredging operation, mathematical dimensional reduction method which uses multivariate primary component analysis is proposed. The method can calculate the contribution rate and cumulative contribution rate of each parameter and then select the principal components which influents the production and energy consumption. These parameters represent the majority of the original data information, while not interrelated with each other. The primary components can be used to guide the regulation and control of the parameters, reduce regulatory parameters and operational complexity and provide a theoretical basis for intelligent automation of dredging operations.

Abstract: Dredging in a contaminated river has been widely accepted to have an impact on the environment; however environmental risk assessment analysis could be costly, time-consuming and difficult to perform. Therefore, a screening method acting as a preliminary risk assessment analysis to screen potential contaminated areas is necessary. The aim of this study is to demonstrate a new screening method for risk assessment analysis in a scenario where economy, time and simplicity factors had been a concern. The development of this method is based on a variation of standard Ecological Risk Assessment. An analysis will be performed on two elements. Firstly, the level of contaminants in the water, groundwater and air (known as the media) and, secondly the behavior of environmental indicators during monitoring of historical dredging. This analysis is performed in order to establish the degree of contamination in an area that is about to be dredged, in where the publicly accessible contamination level in the media and the historical dredging monitoring data will be utilized. Eight dredged sites in Peninsular Malaysia are selected as the case studies of this research. This research showed that Sungai Perlis has a very high total risk value, which could have a fatal impact on its biodiversity if dredging is performed with negligence at this location. This research could provide an opportunity for Malaysia to increase its efforts to avoid dredging impacts without being constrained on time, cost and simplicity factors.

Abstract: The consolidation test was performed to samples of fresh soft dredger fill with heights of 2cm, 3cm and 4cm with full-automatic pneumatic consolidometer. The results show that: the soil sample deforms greatly during the consolidation with significant decrease in water content and small consolidation coefficient. The sample height has negligible effect on the deformation rate, compression modulus, compressibility coefficient, etc., while it is closely related to the consolidation coefficient with an inverse relationship.

Abstract: Cutter suction dredgers (CSD) play a major part in the field of dredging engineering in harbors, fairways, and land reclamation. CSD can continuously mine and transport the slop with good quality while CSD can tackle many types of soil. However, even a component failure, which is connected with parts and components of CSD, can result in no working. Thus, it affects the production capacity and efficiency of dredgers seriously. It is necessary to analyze the failure probability of CSD. The method of Fault Tree Analysis (FTA) is applied to analyze the failure probability of CSD. The method uses logical reasoning and builds a fault tree model by analyzing the relationship between the basic, intermediate and top events. Based on fault tree model of a variety of events " and " " or " relationship, we can obtain minimal cut sets of that cause the event to failure. Then, get the basic probability of the event. Finally, we can calculate the probability of the top events. Under experiments, the FTA method can accurately calculate the failure probability of CSD, and deduce in reverse order the key events that cause the top event. The study on the key events can reduce the failure probability of CSD, enhance its reliability and safety, and improve the efficiency and productivity indirectly. It will also lay a foundation for product configuration optimization.

Abstract: The sludge in rivers, dams and municipal facilities have caused increasing attentions. The airlift water jet can make density difference between sludge and the environment, and make the sludge float automatically. A kind of airlift water jet dredging system is designed and its work properties are analyzed. Mechanical structure analysis shows that the airlift water jet dredging device is low energy consumption and easy of maintenance with low cost. Numerical Simulation shows that the bubble volume ratio will affect the flow performance: the bigger bubble volume ratio will generate higher transport capacity.

Abstract: Daqing River is one of the major rivers flowing into the Dianchi Lake. In this paper, phytoplankton investigation and environmental assessment for the dredged area in Daqing Estuary Section of Dianchi lake in Kunming city was reported. After microscopic identification and counting of 6 water samples(two of them is control plot), the water environment were evaluated by the phytoplankton species and quantity which were assessed by the biological diversity index, including Maglarf, Shanon-Wiener, Simpson diversity index, Pielou index and Berger-Parker dominance index. It’s found that there are mainly 5 species of algae, and among them, Microcystis spp. et al., are the dominant species. So the water is assessed as eutrophication, Heavy sewage. Based on the diversity index analysis, the dredged area sampling sites were relatively higher than the non-dredged areas in biodiversity of phytoplankton. Summarily, the water quality after dredging has been improved to some extent. Phytoplankton biodiversity indicators should be the important water environmental assessment method.

Abstract: As being a vital role affecting the water quality and stimulating the circulation of pollution in native lake, the physicochemical properties of water and the surface sediments in Dianchi Lake dredging area were investigate to determine the level of physicochemical properties of the dredging area, and to evaluate the effects of dredging project. The results showed that the physicochemical properties indicated a more seriously polluted state in Caohai. The effectiveness of dredge work in Caohai was ignorable comparing to Waihai, but it was more obvious in the sediment than in water.

Abstract: Sediment dredging is currently the most commonly selected option for getting rid of contaminated sediments. In this study, the effects of estuary dredging on removing nitrogen and phosphorus were investigated by comparing the different vertical nutrient content between the dredged and un-dredged areas in Dianchi Lake. The results showed that the contents of total nitrogen and total phosphorus in the un-dredged areas were relatively higher than that in dredged areas. Besides, the contents of bio-available nitrogen and phosphorus represented the similar results, only a few dredged spots showed a higher potential releasing capacity. Therefore, with the reduction of internal nutrient loading, it indicated that sediment dredging might be an effective and reliable way to improve such eutrophic lakes.