Papers by Douglas Gaffney
Dredged material having a high percentage of organics and fine-grained silts and clays can presen... more Dredged material having a high percentage of organics and fine-grained silts and clays can present challenges to engineers and contractors attempting to dewater and dispose of the material. Large geotextile tubes have been used on several occasions for containing and dewatering dredged material. The dredging at Nacote Creek in Port Republic, New Jersey provides an excellent case history to describe the dewatering of an organic, fine-grained dredged material within geotextile tubes. Sediment dredged from Nacote Creek was a highly organic, mud/peat that does not readily release its water. The contractor proposed a solution to dewater the dredged material in large Geotex® 46T tubes. The first phase of the project was completed in March 1999. After three months, the first tubes were cut open and the dewatered dredge material excavated, loaded into trucks and removed. The material consolidated to approximately one third its original volume, from 16,000 cubic yards of in situ dredged mate...
Storm events are typically classified as a percent occurrence or return interval based on their p... more Storm events are typically classified as a percent occurrence or return interval based on their peak storm elevation. The stage is the combination of storm surge, astronomical tide and other large spatial scale characteristics. Alternatively, wave heights are classified using the statistical probability of the entire range of wave are more locally affected and of a smaller spatial scale than the storm stage. Intuitively, we know that storms, having superelevated water levels, occur simultaneously with increased wave heights, yet the joint occurrences of both parameters cannot be predicted with confidence based on empirical data. Wave forces and water levels are used in the design of coastal structures and the determination of the level of protection. However, the probabilistic combination of high energy waves and storm stage are not often considered jointly. By considering the joint occurrence of both the water and wave heights, a more complete idea of the actual recurrence interval...
A natural display of bifurcation is observed and related to deterministic chaos theory. A possibl... more A natural display of bifurcation is observed and related to deterministic chaos theory. A possible scenario is proposed from which an eroding dune scarp could be described.
Coastal Engineering Proceedings, 2018
Living shorelines are considered a more natural approach to shoreline stabilization for low-energ... more Living shorelines are considered a more natural approach to shoreline stabilization for low-energy coastlines in contrast to traditional “hard” shoreline armoring methods (i.e. bulkheads). Living shorelines often vary by design and materials, which are optimized for site-specific coastal and environmental conditions, such as wave climate, tidal range, sunlight exposure, etc.; however, the core benefits of all engineered living shorelines are typically the same: reduce shoreline erosion; enhance marine, intertidal, or backshore habitat; and increase resiliency to storm surge and/or sea level rise. While the general benefits of living shorelines are well known, project-specific technical data (i.e. percent of wave energy attenuation, shoreline advancement rates) documenting the effectiveness of living shorelines is more sparse. Moreover, monitoring equipment and analysis techniques required to capture the fine-detailed technical data can prove to be cost and/or labor intensive.
Ports 2010, 2010
Since the publication of the report of MarCom Working Group 21, there has been an increased use o... more Since the publication of the report of MarCom Working Group 21, there has been an increased use of geotextile elements in hydraulic and coastal engineering. For port and waterway managers, it can be difficult to decide whether structures utilizing geotextile components are acceptable alternatives to structures made solely from classical or traditional materials such as stone, and which of the many types of geotextiles are the most appropriate. The goal of the working group is to produce a guideline for the application of geotextiles in waterfront protection. The objective is not to give detailed design procedures for such structures as design guidelines exist elsewhere in the literature. The functions of geosynthetic materials are covered in the guideline, as related to their use in waterfront applications. The guideline also includes a variety of geosynthetic types used in waterfront protection such as geotextiles and geogrids, and fabricated or manufactured products based on geosynthetics such as geotextile tubes and stone-filled marine mattresses. The guidance provides an overview of types, ranges of loads in which the structures can be applied (maximum wave heights, surge and tidal range, and current conditions); and considerations related to aging, durability, and vandalism. Also, environmental aspects are taken into account. It is the Working Group's intention that the final report will provide guidance to professionals in the maritime industry on whether and when to use geotextile elements in various types of waterfront protection and structures. The report should be in publication by late 2010. Copyright 2010 ASCE.
Wetlands Engineering & River Restoration 2001, 2001
(MB-OFDM) Multi-Band Orthogonal Frequency Division Multiplexing is a suitable solution for implem... more (MB-OFDM) Multi-Band Orthogonal Frequency Division Multiplexing is a suitable solution for implementation of high speed data transmission in ultra wideband spectrum by dividing the spectrum into available multiple bands. In MB-OFDM system the most important part is base band of transmitter. In this paper introduced the structure of MB-OFDM system transmitter and the design of transmitter baseband based on FPGA is described in detail. Quartus2 which allow the synthesis of Vhdl code on to Alter's FPGA chip or Xilinx's ISE suit for Xilinx's FPGA chip. The results show that all designed modules has achieved the expected purpose both in precision and resource.
Geotextiles and Geomembranes, 2002
Geotextile tubes are finding increasing market acceptance for dewatering high water content mater... more Geotextile tubes are finding increasing market acceptance for dewatering high water content materials. The success of this application depends on the filtration compatibility between the high water content materials and the geotextiles used to make the tubes. In this paper, 26 pressure filtration tests using four woven geotextiles of various materials were conducted to study soil retention and permeability of the sludge/geotextile system and the possible controlling factors. Based on the test results, the filter cake is not only the major contributor to the retention of fine particles, but also causes a decrease in permeability. Controlling the formation of the filter cake on the inside of the geotextiles tube and thus achieving a balance between soil retention and permeability is vital to a successful project. Surprisingly, initial water content may have a significant effect on the dewatering efficiency and dewatering rate. More testing is recommended to gain a deeper understanding into this relationship.
Geotextiles and Geomembranes, 2011
In order to investigate the use of geotextile bags for dewatering slurries, an analytical model f... more In order to investigate the use of geotextile bags for dewatering slurries, an analytical model for a fluid draining from a hanging geotextile bag is derived and presented in dimensionless form. A data analysis procedure is proposed. Experimental results using water as the fluid with specially constructed geotextile bags are compared with the model and show excellent agreement. The model is applied to data for slurry-filled bags and used to determine the overall permittivity of a hanging bag dewatering system and the fraction of the bag's volume drained as fluid.
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Papers by Douglas Gaffney