Stability of River Dike: Study of Compacted Soils at Very Low Stress
Introduction
River dikes are an elongated natural occurring ridge or artificially constructed fill or wall, which regulates water levels. It is often earthen and often parallel to the course river in its flood plain or along low line coast lines. The main purpose of the artificial dikes are to prevent flooding of the adjoining countryside and to show natural course changes in a waterway to provide reliable shipping lanes for maritime commerce over time; they also confine the flow of river resulting in higher and faster water flow.
From the slope stability point of view of such dike, effective strength parameters give the most realistic solution, particularly with respect to the position of the critical slip surface. However, well defined failures envelop in the low stress range and an accurate estimate of the true cohesion is essential when the stability of soil layer subjected to low consolidation stresses is considered. For typical geotechnical engineering practice, the failure envelop is extended linearly to the stress range and the cohesion intercept is assumed to be zero for normally consolidated soil which is disputed very much in stability analysis. Researcher believe the failure envelop to be curved towards zero in the low stress range.
Objectives
• To study the shear strength behavior and deformation characteristics of river dike soil (mixture of clay, silt, and sand) at very low stress using direct shear test and triaxial compression test.
• To draw the well defined failure envelop and estimate the true cohesion and friction angle at very low stress.
• To check the validity of failure envelop which is extended linearly to low stress range and assumed c...
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...nsors during the test.
Interest
• Stress measurement: Confining Stress, Axial Stress using load sensors
• Strain measurement: Axial strain, Lateral Strain using local displacement transducers
• Pore water pressure measurement in case of undrained test
• Volumetric Strain and Deviatoric Stress
• Relationship between the above parameters
• Nature of failure envelop (linear or curved)
• Cohesion and Friction angle
• Apparent cohesion/True cohesion
• Shear strength of Soil
• Young’s modulus and stress dilatancy response
• Yielding
• Repeatability and reproducibility of soil
• Circular slip analysis
Conclusion and Recommendation
• Behaviour of failure envelop in low stress range
• Validity of linear or curve failure envelop
• Analysis of the true nature of apparent cohesion
• Effect of true cohesion on stability analysis
• Comparision of results with other researcher’s
A major flood on any river is both a long-term and a short-term event, particularly any river basin where human influence has exerted "control" over the ri...
Allow land close to the river to be used for economic gain · Concrete levees are a barrier to the river draining away naturally · Expensive to build & repair · Restrict access to the river Channel straightening Straight channel is cut between two necks of a meander -shortens river. · Shortens river - cuts transport costs · Controls the flow of the river more closely · Evidence now suggests that river Mississippi too powerful - re-cut back to original meander course breaking away from artificial channel. Wing Dikes Structures built out into river to force faster current to midstream.
Elastic strain region at small and big end of connecting rod is shown in figure no. 10. The maximum and minimum equivalent strain values are 0.00033975 and 2.1407e-10 respectively. Due to applied pressure there will be change in original dimensions of the connecting rod and hence strain developed can be
manmade levees, dikes, and other flood control measures, is a case in point. In a
Fatigue failure can be divided in three parts i.e. Crack initiation, Crack propagation and Final rupture.
Yan, F., Feng, X., Chen, R., Xia K., Jin, C., Dynamic Tensile Failure of the Rock Interface
Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid. The phenomenon is most often observed in saturated, loose (low density), sandy soils. This is because the loose sand has a tendency to compress when a load is applied; dense sands by contrast tend to expand in volume. If the soil is saturated by water, then water fills the gaps between soil grains. In response to the soil compressing, this water increases in pressure and attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g. earthquake shaking, storm wave loading) such that it does not flow out in time before the next cycle of load is applied, the water pressures may build to an extent where they exceed the contact stresses between the grains of soil that keep them in contact with each other. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose all of its strength. According to the
Laws such as the lever law and Euler’s Buckling Theorem come into play when testing and competition begins. A structure of wood and glue surely has much more to offer than meets the eye.
Plasticity index of soil: soil suction will be greater in a soil which has greater plasticity index than in the one which has lower plasticity index.
during normal conditions. Dam-like ridges form along the banks of rivers on flood plains and under normal conditions keep the river in its channel. During floods rivers flow over the tops of levees and flood the flood plains that lie adjacent to the river channel. Man has constructed channel walls to "beef up" the natural levees to protect the flood plains. However, all of New Orleans and the flood plain beyond the city is constantly threatened by flooding of the Mississippi River (Madsi, July 99).
Mechanical Engineering 130.2 (2008): 6 - 7. Academic Search Complete. Web. The Web. The Web.
Living in Bangladesh, we have seen quite disastrous mudslides from the past few years. Mudslide is also called a landslide or a land slip. It is a downward mass movement of earth or rock on unstable slopes, including many forms resulting from differences in rock structure, coherence of material involved, degree of slope, amount of included water, extent of natural or artificial undercutting at the base of the slope, relative rate of movement, and relative quantity of material involved. There are numerous facts that can cause a mudslide and there are also numerous effects that it can cause us.
A Flood Hydrograph and the Factors That Affect its Form A flood hydrograph is a graph of two axis, 'discharge' and 'time'. Plotted on the graph is the amount of discharge over a period of time. By looking at a hydrograph, a lot of information and data can be gathered about the river, the precipitation, the surrounding area and vegetation etc. The gradient, height and length of a line can tell you a lot of this information. There are many different factors that can affect the appearance and shape of a hydrograph.
... although we may never be able to understand exactly what soil failures can occur when a natural disasters take place, as time goes on and testing instruments and materials advance we will hopefully have a better understanding of what we can do to avoid soil failures and come up with a better and more sufficient method of improving the soils structure and strength permanently. While researching the information for this report I feel I have a much better understanding for construction geo-technics and foundations especially regarding the deformation, liquefaction and pile information related to this specific event. I hope to carry the information I have learned from this event into the construction field and apply them towards an authentic project that’s taking place and know that the information, regarding soils, I have given input on will be precise and accurate.
Diversion dams are mainly built to lessen the effects of floods and to trap sediment.3 Overflow dams are designed to carry water which flow over thier crests, because of this they must be made of materials which do not erode. Non- overflow dams are built not to be overtopped, and they may include earth or rock in their body. Often, two types of these dams are combined to form a composite structure consisting of for example an overflow concrete gravity dam, the water that overflows into dikes of earthfill construction.4 A dam's primary function is to trap water for irrigation. Dams help to decrease the severity of droughts, increase agricultural production, and create new lands for agricultural use.