What determines whether a slope will fail or stay in place? Adapted from Surface Process Hazards-Unit 3, Part 1, Physica

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What Determines Whether A Slope Will Fail Or Stay In Place Adapted From Surface Process Hazards Unit 3 Part 1 Physica 1 (151.62 KiB) Viewed 63 times

What determines whether a slope will fail or stay in place? Adapted from Surface Process Hazards-Unit 3, Part 1, Physical Factors: Sarah Hall, College of the Atlantic & Becca Walker, Mt. San Antonio College In this exercise, you will calculate the physical factors that contribute to mass movements of Earth materials. As we have discussed any scenario in which the driving force exceeds the resisting force will cause a mass movement. Part 1: Understanding the force of gravity The force of gravity (FG) is a mass-dependent force that is directed downward toward the center of the Earth. Figure 01 illustrates a block sitting on a flat surface. In order to calculate the force of gravity (also called the weight, W), we need to know the mass of the block and the acceleration due to gravity (g). The value for g (acceleration due to gravity) is 9.8 m/s². F =W= mg Figure 01 FV N FN: F₁ Figure 02 FN = W cose Fs = W sin W=F₁ 0( As seen in Figure 02, when a block is sitting on a slope (0) the force of gravity (FG) can be broken up into the normal force (FN) and the shear force (Fs). The components of these forces can be calculated by multiplying the weight (W or Fc) by the cosine or sine of the slope (0). In the next few questions, we will use a simple model to identify and quantify these forces/stresses that are involved in mass wasting. 1. In the space below, indicate (label) which force keeps the block from sliding (resisting force) and which force promotes sliding (driving force) of the block. Fs:
2. Consider that the block is 20 m long, 10 m wide, and 10 m tall. In the space below, calculate the volume (V) of the block and the area (A) under the block. 3. We can use the density of the material to determine the mass of the block. In the space below, rearrange the equation for density to solve for mass. TABLE 01 4. The density of the block depends on what material the block is made from. Table 01 (below) shows the average densities for 3 different kinds of Earth materials. Using this data, calculate the block's mass if it were made in each of the materials in the table. I calculated the first row for you. Material Sand Limestone Basalt ~Density Mass Weight FN (30 deg) (kg/m³) (kg) (kg m/s²) (kg /ms') m P= V -1.8 P = density m = mass V = volume Fs (30deg) FN (50 deg) (kg/ms²) (kg /ms²) Fs (50 deg) (kg/ms²) 3,600 35,280 30,553 17,640 22,677 27,026 5. Using the masses that you calculated above and the equation for force, calculate the weight of each block (W) and record your answers in the table. Hint: Weight = mass * gravitational constant
So for the weight of the sand block, you would calculate 3,600 kg * 9.8 m/s² = 35,280 kg m/s² Part 2: Understanding the concept of stress As you know from our lecture, stress (force per area) is the pressure under the block of material. Pressure can be measured in Pascals (Pa), bars, pounds per square inch (psi), or as a combination of the units we have been using. 6. Using the same block dimensions and a slope angle of 30°and 50°, calculate the normal stress and shear stress of blocks of the 3 materials. Write your answers in units of Pascals (kg/ms²) per unit area on the table. There is no need to do any unit conversions. Hints: When you do your cosine and sine calculations remember your values are in degrees, not radians. You do not need to completely understand trigonometry or college algebra to do this but you do need to understand that these degrees can be expressed in multiple ways. For those who do not remember or do not know how to do this, I would suggest that you quickly google cosine. For example, google "cosine of 30 degrees" and it should give you the right answer. So, to do the first calculation that I did above I would multiply the Weight of the Sand Block * the cosine of 30 degrees (slope of the ground surface). 35,280 kg m/s² * 0.866= 30.553 kg m/s² 7. Given your answer to the previous calculations, which blocks will slide OR stay in place at these given slopes? Continue on next page
Part 3: Utah Hazards Below is a map of part of Utah Valley. UVU, Rock Canyon Park, and the Sherwood Hills neighborhoods are labeled. Rock Canyon is a popular destination for outdoor activities. Click HERE for the geology of Rock Canyon in Provo, Utah. Vineyard Linky Powell Slough Waterfow Mangement 29 University 9 Orem kertide l Sherwood Hills ومت Sherwood Hills is located in Provo, Utah. It is among the largest residential developments on a landslide in the state of Utah. Most of Sherwood Hills sits on a prehistoric landslide. Furthermore, the neighborhood lies just below an earthquake fault that runs along the base of the mountains. Below there are some images of landslide evidence in Sherwood Hills. When you compare the landslides between Sherwood Hills and Rock Canyon, think about the types of landslides we've discussed in the lecture and analyze which ones would occur at which location. As a reminder when answering short answer questions put enough depth that the grader/instructor can understand that you have a firm understanding of the material. Use key words and phrases. Do not be so vague that we need to read between the lines. Be explicit but concise. Also please either bold your answers or put it in a different color.
8. Describe the geologic hazards (types of landslides and hazards associated with earthquakes) that are more likely to occur in the Sherwood Hills area than the UVU area. 9 Describe the geologic hazards (types of landslides and hazards associated with earthquakes) that are more likely to occur in the Rock Canyon Park area than the UVU area.
10. Describe the geologic hazards (types of landslides and hazards associated with earthquakes) that are more likely to occur in the UVU area than the Sherwood Hills area. 11. What are the preventive and remediation steps we could take to manage the potential hazards in Utah Valley?