Part 2: Fronts

Pegmatites A. can contain crystals up to tens of centimetres across.B. occur in tabular intrusions called laccoliths. C. are an igneous rock type, distinguished by their unusual composition. D. have intruded at great depth and cooled very slowly.

5. Which of the three wells will produce the most gas assuming that hydraulic fractures cut vertically for 100 feet from a horizontal well? Why? As a general rule, hydraulic fractures will propagate upward about three times as much as downward.

3.Calculate the geostatic vertical effective stress (o'vo) at a point located at a depth of 0.5 meters in a dry sand layer. Note: this problem (and the rest of this HW) is not related to HW 3 problems.

Complete this problem. An undrained direct shear test was conducted on a specimen of clay. The test was conducted with a normal stress of 60 kPa. The data are shown on the right. Determine the critica lstate undrained shear strength of the soil.

Intrusive igneous rocks A. cool slowly and are coarse-grained. B. are rocks like basalt, andesite, and rhyolite. C. are fine-grained because they cooled slowly. D. are never seen by humans, because they form deep in the Earth and are never exposed at the surface.

4. At the front face of a retaining wall, the toe of the wall is 3 metres below ground level. The horizontal component of the active thrust on the wall is 226 kN per lineal metre, and the vertical component of the load on the base is 423 kN per lineal metre.The soil is sandy and has a density of 1.75 Mg/m³, o'crit =27°. Find the passive resistance against the front of the wall. Calculate the ultimate limit states (ULS) for sliding (angle of internal friction is 20°).

A seismic refraction study made for an area pro-vides the following field data: (a) Graph the travel-time data and determine the seismic velocity for the surface layer andthe underlying layer. ) Determine the thickness of the upper layer. O Using the seismic velocity information, give the probable earth materials in the two layers.

3. For each block diagram below: (20 pts )a. Complete the top of the block as a geologic map. Include the proper map symbols for fold axes and faults where applicable. Label with strike and dip symbols (2-4 per map as needed). b. Construct a structure contour map for the top of unit Dk, using the surface of the block (0m)as the datum. Be as accurate as possible. c. For each block diagram, two wells are drilled at sites A and B to reach the target unit, Dk.Which well must be deeper? Approximately how much deeper is it?

Using Bishop's simplified method of slices determine the factor of safety in terms of effective stress for the trial circle in the slope as shown in Figure 4 (Q5). The properties of the sandy soil are as follows: ys = 20 kN/m³ and o = 30°. Divide the slope cut into at least four slices. Show your values for the heights of the slices andfor a, the inclination of the base to the horizontal both graphically and in a table with the additional information that you need to make the calculation for the factor o fsafety. Full calculation is required for two slices ONLY. F_{s}=\frac{1}{\sum \sin \alpha w} \sum\left[\frac{\left[(w-u b) \tan \varphi_{c n i}^{\prime}\right]}{\left(\cos \alpha+\left(\tan \varphi_{c r i i}^{r} \sin \alpha / F s\right)\right.}\right] (b) If the slope of interest is associated with cohesive soil explain the effect of tension crack likely to have on the slope slip.

2. (50 pts) A Mechanically Stabilized Earth (MSE) wall is to be constructed as shown in the figure below. Answer the following questions regarding this wall. a) (5 pts) What is the Rankine active earth pressure coefficient that should be used? b) (15 pts) What is the magnitude, direction, and height of the lateral pressure resultant(Fa)? What are the magnitudes of the horizontal and vertical components of the lateral pressure resultant? c) (10 pts) What is the total overturning moment if the reference point is placed at thetoe of the wall? d) (10 pts) What is the total resisting moment if the reference point is placed at the toeof the wall? (5 pts) Does the wall meet the minimum factor of safety for overturning (2.0)? f) (5 pts) Does the wall meet the minimum factor of safety for sliding (1.5)?