Lab 8 - Topographic Survey and Earthwork Assignment (2)

CE 301 – Civil Engineering Systems Lab 8 – Earthwork Calculations Page 1 of 4 Laboratory 8: Topographic Surveying and Earthwork Calculations Background Before construction can begin on a plot of land, the area must be leveled and prepared. In some cases, quality fill soils will be trucked in to level out the site and provide a strong foundation. For other projects, a basement level will be constructed by excavating deep into the ground at the building location. These choices are dependent on the designer’s needs and the quality of the soil on site. The engineer will then prepare a cost estimate for the excavation or fill that is needed. Problem Statement After considering your recommendations from the closed traverse survey of the property, the University of Texas has selected the location and dimensions for the proposed building. The footprint is aligned with the corner of San Jacinto and Dean Keeton with dimensions of 100 feet by 80 feet as shown below. Figure 1 - Building footprint and location You have decided that you will level out the area by excavating soil only to avoid the material and construction costs of importing fill soils. The top layer of soil on site contains substantial organic material, which is too soft to support the weight of the building. In this laboratory, you will establish the elevation of points on a grid corresponding to the building footprint. The foundation for the building will be constructed at an elevation two feet below the ground surface at the lowest observed point. You will then calculate a cost estimate for the earthwork that must be done to excavate the soil down to this elevation. 0N 20N 40N 60N 80N 0’ 50’ 100’ E. Dean Keeton St. San Jacinto Blvd.

CE 301 – Civil Engineering Systems Lab 8 – Earthwork Calculations Page 2 of 4 Data Collection Fifteen points have been marked on a grid pattern as shown in Figure 1. Find the elevation of each point using an automatic level and a level rod.  Set up your automatic level anywhere in the area where you have a view of Benchmark 34 and the grid points  Take a backsight on the benchmark. Use this to establish your height of instrument by the following equation: ?? = ? ?𝑀 + ?𝑆  Take a foresight on each grid point  If you cannot get a clear reading on every grid point from your original set up, move your automatic level. Be sure to take a backsight on the benchmark from your new location and to calculate the new height of instrument.  Find the elevation of each point using the following equation: ? ? = ?? − ?𝑆 ? Data Analysis Calculate a cost estimate for the earthwork required to prepare the site for construction of the building.  Establish the grade elevation for the building by taking the minimum observed elevation and subtracting 2 feet  Calculate the change in elevation at each point from the observed ground elevation to the grade elevation  Use the trapezoidal rule to calculate the total c ut area for each cross section (at 0’, 50’ and 100’) ? 𝑡𝑟𝑎??𝑧?𝑖?𝑎𝑙 = 𝑤 × ( ℎ 1 2 + ℎ 2 + ℎ 3 + ⋯ + ℎ ? 2 ) Where: w = width between points h = change in elevation at each point n = number of points measured on cross section  Use the average end area method to calculate the total cut volume between cross sections 𝑉 1−2 = 𝐿 × ( ? 1 + ? 2 2 ) Where: L = length between cross sections A = area of cross section  Sum the total volume for excavation and apply a soil swell factor of 1.1. The swell factor is used to account for the amount that soil will expand after excavation. The expanded volume must be disposed of, so this value is used for the cost estimate.  Calculate the cost of excavating and removing the total volume of soil using a unit cost of $12 per cubic yard of soil. Make sure to convert your units from feet to yards correctly.

CE 301 – Civil Engineering Systems Lab 8 – Earthwork Calculations Page 4 of 4 Report Requirements Your report should follow the format given in the Lab Curriculum and include the following information:  A summary of the background theory and purpose for this lab (*Introduction)  A thorough description of the procedures and equipment used in data collection (*Experimental Procedures)  A table presenting the calculated elevations and a table presenting the three cross-sectional areas, the two volumes between the cross sections (V 1-2 and V 2-3 ) and the total volume (*Experimental Data and Discussion)  A brief discussion of the sources of systematic and random error in this lab (*Experimental Data and Discussion)  Diagrams of the three cross sections used for calculations meeting the following requirements (*Design Application) o Neatly hand drawn or computer generated with the scale and units clearly marked o Ground elevation and grade elevation shown  The associated cost estimate (*Design Application)  A summary of the purpose and the findings of the lab (*Conclusion)  Your data sheet, including your field notes, attached as Appendix A  Sample calculation of one ground elevation, one cross sectional area, and one volume attached as Appendix B *Indicates section of the lab report under which the report requirements should be placed.