Full-scale Case Histories Research Articles

EFFECT OF WEATHERED SURFACE CRUST LAYER ON STABILITY OF MUAR TRIAL EMBANKMENT

his paper attempts to evaluate the effect of surface crust layer on the stability and deformation behavior of embankment. A full-scale case history trial embankment constructed on Muar flat in the valley of the Muar River in Malaysia was modeled and analyzed. The Muar trial embankment was simulated in two- and three-dimension (2-D and 3-D) utilizing finite element programs PLAXIS 2-D AND PLAXIS 3-D FOUNDATION, using staged-construction procedure. Sensitivity analysis was performed by varying the thickness of weathered crust layer beneath the embankment fill, i.e., three models of embankment with no surface crust, 1 m surface crust and 2 m surface crust layer. Predictions were made for the vertical and the horizontal displacements of the embankment. Factor of safety for each meter increase in the embankment height was defined until the failure is reached. It is concluded that the bearing capacity of the ground and the deformation behavior of the embankment were sensitive to the thickness of the weathered crust layer. The surface crust layer has a positive effect on the stability of the embankment and consequently reduces the settlement and increases the failure height of the embankment fill up to 37%.

New direction for earth reinforcement: disaster prevention for earthfill dams

ABSTRACT: A large number of geosynthetic-reinforcing technologies for embankments and retaining walls have been proposed and developed, and the behaviour of these structures has been evaluated using laboratory tests and field tests, as well as full-scale case histories. Yet a great number of embankments have failed in Japan owing to strong seismic loads and heavy rainfall. Significant improvements are required in the construction of earthfill dams to prevent these failures. This paper reviews the characteristic features of the damage to small earthfill dams that has taken place during earthquakes as well as heavy rainfall. The paper then describes a new technology using geosynthetic soil bags with extended tails stacked on the downstream slope to construct earthfill dams that are highly stable against earthquakes as well as heavy rainfall leading to overtopping by flood water. Some fundamental aspects of the stability of embankments reinforced by soil bags and seismic behaviour are examined using static loading, hydraulic breach tests and shaking-table tests.

Settlement of Embankments on Soft Clays

The topic of consolidation of clays was partially chosen because it was Terzaghi's first major contribution to what we now call geotechnical engineering, as well as due to the author's years of interest in the topic. This manuscript addresses practical aspects of the prediction of time-dependent settlement of embankments on soft clays. The problems addressed include site exploration; solid modeling of field data; problems associated with taking, handling, and testing soil samples; efficient reduction, storage, and display of laboratory data; and analytical methods to handle such routine problems as effective-stress dependent coefficients of consolidation, large strains, nonlinear stress-strain curves, multidirectional flow, and secondary effects. Furthermore, this manuscript considers the lessons we have learned from analysis of full-scale case histories. In spite of the range of topics, this is not a state-of-the-art paper, in that no attempt is made to provide a cross section of references on all relevant topics.

99/02402 Biological fluidized bed treatment of wastewater from by-product coking operations: full scale case history

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles. The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps. The fuel pump(s) are driven in a conventional manner, for example, using a fuel-rich gas-generator cycle. Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4% lower while providing much lower oxygen temperature, more efficient tank pressurizing system and built-in roll control. This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle. Another semi-expander cycle can be considered as an improvement of gas-generator cycle. All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen. Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse, via optimization of mixture ratio. It is especially the case for upper stage engines. The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization. It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines. Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses. It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions. A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles. The newly-developed software RECS was used for the comparative analysis of engine cycles.

Settlement of Embankments on Soft Clays (The Thirty-First Terzaghi Lecture)

The topic of consolidation of clays was partially chosen because it was Terzaghi's first major contribution to what we now call geotechnical engineering, as well as due to the author's years of interest in the topic. This manuscript addresses practical aspects of the prediction of time-dependent settlement of embankments on soft clays. The problems addressed include site exploration; solid modeling of field data; problems associated with taking, handling, and testing soil samples; efficient reduction, storage, and display of laboratory data; and analytical methods to handle such routine problems as effective-stress dependent coefficients of consolidation, large strains, nonlinear stress-strain curves, multidirectional flow, and secondary effects. Furthermore, this manuscript considers the lessons we have learned from analysis of full-scale case histories. In spite of the range of topics, this is not a state-of-the-art paper, in that no attempt is made to provide a cross section of references on all releva...

SAND-BYPASS AND SHORE EROSION, BRIDGMAN, MICHIGAN

The objectives of this paper are two-fold: a. Demonstrate by means of a well-documented full-scale case history in the Great Lakes that beach nourishment can mitigate shore damage due to a littoral barrier; b. Detail a methodology for analysis of the effectiveness of mitigation measures which lead to conclusions on the needed frequency of nearshore soundings as a tool for monitoring. In 1970 a temporary harbor was installed by private interests along the southeastern Lake Michigan shoreline near Bridgman, Michigan, (Figure 1). The harbor was necessary to protect floating plant involved in building a large privately-owned electric generating facility. The harbor was constructed of steel sheet pile and extended lakeward about 125 meters from the water's-edge to a depth about 3 meters below low water datum (LWD)2. Net littoral transport is about 75,000 cubic meters per year southward. The updrift and downdrift lakebed and bluff materials consist of sand. To ensure that this littoral barrier would not have an adverse effect on adjacent properties it was necessary for the Corps of Engineers to impose stringent requirements for issuance of a Federal permit for the installation. Bypass of at least 75,000 cubic meters per year of sand was required to mitigate potential erosion of downdrift beaches due to interruption of littoral transport. The permit also required intensive monitoring of the shoreline to ensure that any adverse effects of the harbor would be promptly detected and remedied. The monitoring consisted of: a. Monthly 1:3000 scale aerial photographs of the shoreline sixteen kilometers north (updrift) to sixteen kilometers south (downdrift) ro\-fF tthheo htla'i rVtbt-lof\rv>. b. Monumenting and thrice-yearly measurement of backshore-nearshore profiles spaced 150 meters apart, for a distance of 2450 meters north and 2450 meters south of the harbor, extending about 900 meters lakeward to about -8 meters LWD (Figure 2). The nearshore soundings were made by acoustic sounder every 30 meters along each profile. The survey boat was located along the profile by triangulation. Backshore profiles were provided by photogrammetric mapping.