# A homeowner want to level a rear yard – You visit the site

A homeowner want to level a rear yard. You visit the site and realize that the work will require the construction of an about 5-ft-tall retaining wall. Your subsurface exploration indicates that the soil in the yard is homogeneous medium to fine SAND

## A homeowner want to level a rear yard – You visit the site

A homeowner want to level a rear yard. You visit the site and realize that the work will require the construction of an about 5-ft-tall retaining wall. Your subsurface exploration indicates that the soil in the yard is homogeneous medium to fine SAND with trace amounts of silt (USCS Classification SP) to a depth of 25 ft below ground surface. N-values suggest that the material is classified as NYC Building Code Class 3b material; groundwater was not encountered. Laboratory tests indicate that the sand has a moist unit weight of 122 pcf and an angle of internal friction of 33°.

PROBLEM STATEMENT
Size the retaining wall such that it has a geotechnical factor of safety against sliding and overturning of 1.5.

Assumptions
Assume a vertical surcharge of 300 psf is applied on the high side of the wall.

The wall foundation must bear 4 ft below the lowest grade for frost protection.

The stem of the wall must be a minimum of 12-inches thick.

The wall footing must be a minimum of 12-inches thick.

Ultimate friction factor for mass concrete against clean fine to medium SAND is 0.4.

Consider passive pressure in the analysis.

Lateral pressures due to the surcharge have a uniform distribution based on a pressure equal to 50 percent of the vertical pressure.

Unit weight of reinforced concrete is 150 pcf.

### Assignment:

1) Produce an engineered-quality scaled drawing.

2) Include your calculations showing your assumptions, pressure diagrams and resultant forces.

3) What is the applied bearing pressure under the wall?

4) Is the applied pressure less than the Building Code allowable?

5) If passive pressure is discounted, what is the resulting factors of safety?

6) Provide a cover letter with your submittal.

NOTE: Your calculation must be on engineering paper, they must be neat and without scribbled correction.

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