Surface Processes: Worked Examples

At site A, granite breaks into angular fragments whose minerals remain unchanged. At site B, petrography shows feldspar alteration to kaolinite with dissolved constituents leaving in water. Classify the dominant described process and assess the claim that all resulting clay must be expansive.

A proposed footing site has an O–A–E–B–C–R profile in the conceptual diagram. The B horizon contains accumulated clay. No strength, compressibility or groundwater measurements exist. Can the footing bearing level be approved from the horizon sequence?

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A potential sliding plane has total normal stress 40.0 kPa, zero pore pressure and driving shear stress 25.0 kPa. Effective parameters are $c'=10.0\ \mathrm{kPa}$ and $\phi'=20.0^\circ$. Find available shear resistance and its ratio to demand.

For a second supplied stress state, retain total normal stress 40.0 kPa and parameters $c'=10.0\ \mathrm{kPa}$, $\phi'=20.0^\circ$, but use pore pressure 15.0 kPa and driving stress 28.0 kPa. These are prescribed compatible inputs; no particular rainstorm-to-stress law is assumed. Calculate the new ratio.

A uniform infinite layer has $\beta=30.0^\circ$, vertical depth $z=5.00\ \mathrm{m}$, unit weight $\gamma=20.0\ \mathrm{kN/m^3}$, $c'=10.0\ \mathrm{kPa}$, $\phi'=25.0^\circ$ and zero basal pore pressure. Calculate normal stress, driving stress and the resistance/demand ratio.

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Use the preceding infinite-layer inputs. First set the prescribed basal pressure ratio $r_{\mathrm{n}}=0.400$ while holding unit weight fixed. Then find the pore pressure giving a model ratio of exactly 1.00. This limiting balance is an algebraic reference, not a design target.

For $\beta=30^\circ$, $\phi'=25^\circ$, $\gamma=20.0\ \mathrm{kN/m^3}$ and zero pore pressure, compare vertical depths 5.00 m and 10.0 m. First use zero cohesion, then use $c'=10.0\ \mathrm{kPa}$.

The simulator is set to zero slope angle, zero cohesion and zero friction angle, with positive unit weight and depth and zero pore pressure. Determine the driving stress, available shear resistance and meaning of their ratio.

A two-dimensional block weighs 5000 kN on a plane inclined at 45.0°. There is no cohesion or uplift, and the friction angle is 30.0°. A given horizontal anchor force of 3000 kN acts into the slope. Calculate the global ratio of available resistance to gravity driving force, including anchor clamping and its upslope component.

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Use the preceding block's weight, angle and friction, with no cohesion or uplift. An exercise specifies a global force-ratio target of 1.50. This is a supplied arithmetic target, not a universal design criterion. Find the horizontal force required by this model.

A survey after high flow records a depression around a pier and a lower bed across the channel. No event-time measurements or foundation movements are available. Using the diagram, distinguish possible processes and assess the claim that the local depression proves why the bridge moved.

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