Table of Contents
1. Question 1 1
1.1. FOUNDATION ON THE TOP OF A SLOPE 1
1.2. FOUNDATION ON THE FACE OF A SLOPE 3
2. Question 2 5
3. References 6
QUESTION 1
Please describe the problem of the bearing capacity of foundations under combined loads in slope (see Figure 1). Will the bearing capacity decrease? If so, what are the causes?
Figure 1- For question 1
FOUNDATION ON THE TOP OF A SLOPE
Meyerhof(1957) indicated that for a foundation located on or near the slope, the plastic zone on the side of the slope is relatively smaller than those of similar foundation on leveled ground and subsequently the bearing capacity of the foundation near slopes reduced. He claimed a solution for the ultimate bearing capacity of foundations on or near slopes (Figure 1.1) with those from stability analysis to form the equation as following
q_u=c^'.N_cq+1/2 γ.B.N_γq
Figure 1.1- Failure plane for the shallow foundation near or on slope
where Ncq is a factor represents the combined effect of the cohesion of the soil and the overburden pressure and N_γq is a coefficient for the combined effect of the shear resistance of the soil beneath the foundation and overburden pressure. The above equation is only for the foundations on or near slope that have distance b from the top of the slope. Meyerhof(1957) also suggested charts for the bearing capacity factors(N_cq and N_γq).
The theoretical variations of Ncq for a purely cohesive soil (ϕ=0) and N_γq , for a granular soil (c = 0), and these variations are shown in Figure 1.2 and 1.3 .
For purely cohesive soil(ϕ=0) →〖(N〗_γq=0) (Figure 1.2) →q_u=c^'.N_cq
For granular soil (c=0) →〖(N〗_cq=0)(Figure 1.3) →〖 q〗_u=1/2 γ.B.N_γq
It is important to note that, in using Figure 1....
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...s to be more uniform.(Venkatramaiah, 1995)
Figure 2.1 - Contact pressure distribution under a rigid foundation loaded with a uniform pressure.(Venkatramaiah, 1995)
For cohesive soil extra pressure can cause stress to shear the soil around the perimeter, the contact pressure at the edges of foundation will be maximum, while it will lessen toward the center. However, for non-cohesive soil (e.g. sand), the maximum contact pressure will be found at the center of the base and will reduce toward the edge because the soil is pushed aside at the edges due to the reduced confining pressure.
References
Das, B. M. (2009). Shallow Foundations: Bearing Capacity and Settlement, Second Edition. GB: CRC Press Inc.
Fang, H. Y. (1990). Foundation Engineering Handbook: Springer US.
Venkatramaiah, C. (1995). Geotechnical Engineering: New Age International Pub. (P) Limited.
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... 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.
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Geotechnical Engineering covers the engineering properties of soils, the fundamentals of soil mechanics, and the application of geotechnical data and fundamentals to the design of foundation elements, earth-retaining structures, excavations, earth embankments and highway pavements.
Chua, Ian Y. H. Civil and Structural Engineering Resource Web. 29 Jan. 2000. 2 Mar.