The document provides information about site development and excavation for construction projects. It discusses developing the site, including performing a site analysis to evaluate soil types, drainage, and other elements. It also describes different types of excavation including open excavations, trenches, and pits. Finally, it discusses various methods for supporting excavations, such as sheeting, soldier beams and lagging, sheet piling, tiebacks, contiguous bored piles, secant piles, slurry walls, and dewatering when below the water table.

1. Site Development: Excavation & Foundations

2. Site Development: Excavation & Foundations Part 1: Site Development and Excavation Developing the Site  Soils  Green Building Strategies: Sustainable Sites  Elements of Excavation 

3. Developing the Site Buildings do not exist in isolation. They are conceived to house and support a range of human activities in response to sociocultural, economic, and political needs, and erected in natural and built environments that constrain as well as offer opportunities for development. We should therefore carefully consider the environmental forces that a building site presents in planning the design and construction of buildings. Frank Ching, Building Construction Illustrated, 3 rd ed.

4. Developing the Site Soil Topography Grade & Slope Protection Plants & Trees Solar Radiation and Orientation Site Drainage Wind Zoning Ordinances Site Access & Circulation Pedestrian Circulation Vehicular Circulation & Parking Utilities (electrical, water, gas, communication) Hardscaping and Impervious Surfaces Sustainable Strategies Elements to consider:

5. Developing the Site Site Analysis must be performed to evaluate the data presented by these elements. Site Analysis is the process of studying the contextual forces that influence how we might situate a building, lay out and orient its spaces, shape and articulate its enclosure, and establish its relationship to the landscape. Any site survey begins with the gathering of physical site data. Frank Ching, Building Construction Illustrated, 3 rd ed .

6. Soil All buildings rely on soil for their ultimate support. The underlying foundation is effected by the soil’s strength under loading.

7. Soil The measure of a soil’s strength is its bearing capacity in pounds per square foot (psi). Factors that determine the bearing capacity of a soil are:  stratification (classification)  composition  density of soil bed  water  freezing/thawing  permeability  variations of particle size

8. Soil Types Affects the type and size of a building’s foundation system Affects the drainage of ground and surface water Affects the types of plant material able to grow on a site

9. Soil Types ROCK Continuous mass of earth mineral are firmly bonded together Removal by blasting or drilling Located beneath layer(s) of soil Strongest and most stable of “soil” that a structure can be supported

10. Soil Types SOIL Unconsolidated mineral particles or conglomerates located at the top layer of the earth’s crust Removal by lifting or digging Boulder: two hands or heavy equipment to lift Cobble: one hand to lift Gravel: pinch between fingers Sand: flows through fingers

11. Soil Types SILT Granules are equal in size and diameter Range in size .002 to .00008 inch Found mostly on river beds and close to waterways Highly susceptible to frost action Poor permeability and drainage Bearing capacity of 2000 psf Frictional/Cohesionless: “loose”

12. Soil Types CLAY Particles are plate-shaped Range in size less than .00008 inch Very close in characteristics to SILT Cohesive: “sticks together” Does not easily “cave-in”

13. Soil Types ORGANIC SOILS Peat, topsoil High content of organic matter (plants) Spongy & compress easily Slightly susceptible to frost action Poor permeability and drainage Great for the perennials, unsuitable for foundations Organic soils consist of fully or partially decayed plant matter, compressive and unsuitable for foundations

14. Soil Types STRADA Superimposed layers of different soils Mixtures of several different soils Silty-gravels Gravelly sands Clayey sands Silty clays

15. Soil Stratification (classification) Particle size Coarse grained (gravel & sand) Fine grained (silt & clay) Particle shape Spherical or ellipsoidal, shaped by mechanical weathering Gravel, sand & silt Flat, plate-like, large surface area to volume ratio Behavior influenced by electrostatic forces and presence of water Cohesion Cohesive soils are fine grained and particles are attracted to each other in the presence of water. Non-cohesive soils are course grained and are not attracted to each other

16. Soil characteristics by particle size coarse-grained cobbles 60mm coarse gravel 19mm fine gravel 5.5mm coarse sand 2.0mm medium sand 0.6mm fine sand 0.08mm fine-grained silt > .08mm clay > .08mm A sieve is an open top container with a wire mesh bottom used for screening particles. The are used to analyze particle size distribution of soils & concrete aggregates.

17. Soil Types

18. Additional factors of Soil Stability How a soil will retain water Rock, gravel, sands are more stable soils Clay is considerably unstable Swells when water is absorbed Dries when water is squeezed and evaporated

19. Additional factors of Soil Drainage How water withdraws from the soil Water passes easily through gravels & sands Water passes slowly through silts & fine sands Water is absorbed by clay

20. How do we know what type of soil is best? Perform a Soil Test Penometer Test Weight is dropped on rod and distance into soil is measured Test Pits Small excavations to observe soil, adjacent conditions and take samples Soil Borings Core sample, drilled into the earth, sample removed and analyzed. Each layer is analyzed and calculations for bearing capacity are made

21. Soil sampling and testing Soil sampling Test pit method Test boring method Also allows for standard penetration test on site Laboratory testing Sieve analysis Determines particle size distribution Soil classification Moisture content Dry density Liquid limit, plastic limit Compressive strength Shear strength

22. Test Boring Equipment Page 514 in textbook Figure 21.2 Picture A: truck-mounted drilling machine boring a hole in the ground with a cutting tip at the end of a hollow pipe stem. During the drilling operation, compressed air is pushed through the hollow stem to suck the drilled soil out to keep the boring clean. Picture B: A hollow pipe stem with a typical cutting bit.

23. Page 515 in textbook Soil Sample Figure 21.3: Soil samples obtained from borings through the use of a sampling tube are wrapped in plastic, labeled with date of sample, location of boring at the site, depth, and so on and sent to the soil testing laboratory. For an example of a Test Boring Log, see page 516 in textbook. Then refer to pages 543-546 for Principles in Practice, further explaining the data show in the log.

24. Site preparation prior to construction Fencing site parameters including silt fencing property fencing Locate and mark utility lines Water, gas, electrical, communication Demolish unneeded structures and utility lines Remove trees, brush, topsoil, debris Prepare staging area

25. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Prerequisite 1: REQUIRED Construction Activity Pollution Prevention Intent To reduce pollution from construction activities by controlling soil erosion, waterway sedimentation and airborne dust generation. Requirements Create and implement an erosion and sedimentation control plan for all construction activities associated with the project. Potential Technologies & Strategies Create an erosion and sedimentation control plan during the design phase of the project. Consider employing strategies such as temporary and permanent seeding, mulching, earthen dikes, silt fencing, sediment traps and sediment basins. Category: Sustainable Sites

26. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 1: 1 point Site Selection Intent To avoid the development of inappropriate sites and reduce the environmental impact from the location of a building on a site. Category: Sustainable Sites

27. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 1: 1 point Site Selection Requirements Do not develop buildings, hardscape, roads or parking areas on portions of sites that meet any of the following criteria: Prime farmland as defined by the U.S.D.A. Previously undeveloped land whose elevation is lower than 5 feet above the elevation of the 100-year flood as defined by FEMA Land specifically identified as habitat for any species on federal or state threatened or endangered lists Category: Sustainable Sites

28. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 1: 1 point Site Selection Requirements Do not develop buildings, hardscape, roads or parking areas on portions of sites that meet any of the following criteria: Land within 100 feet of any wetlands Previously undeveloped land that is within 50 feet of a water body, defined as seas, lakes, rivers, streams and tributaries that support or could support fish, recreation or industrial use, consistent with the terminology of the Clean Water Act Land that prior to acquisition for the project was public parkland, unless land of equal or greater value as parkland is accepted in trade by the public landowner Category: Sustainable Sites

29. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 1: 1 point Site Selection Potential Technologies & Strategies During the site selection process, give preference to sites that do not include sensitive elements or restrictive land types. Select a suitable building location and design the building with a minimal footprint to minimize disruption of the environmentally sensitive areas identified above. Category: Sustainable Sites

30. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 2: 5 points Development Density and Community Connectivity Intent To channel development to urban areas with existing infrastructure, protect greenfields, and preserve habitat and natural resources. Requirements Option #1: Development Density Option #2: Community Connectivity Potential Technologies & Strategies During the site selection process, give preference to urban sites with pedestrian access to a variety of services Category: Sustainable Sites

31. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 3: 1 point Brownfield Development Intent To rehabilitate damaged sites where development is complicated by environmental contamination and to reduce pressure on undeveloped land. Requirements Option #1: Develop a contaminated site Option #2: Develop on a site defined as brownfield by AHJ Potential Technologies & Strategies During the site selection process, give preference to brownfield sites. Identify tax incentives and property cost savings. Coordinate site development plans with remediation activity, as appropriate. Category: Sustainable Sites

32. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 4.1: 6 points Alternative Transportation – Public Transportation Access Credit 4.2: 1 point Alternative Transportation – Bicycle Storage & Changing Rooms Credit 4.3: 3 points Alternative Transportation – Low-Emitting and Fuel Efficient Veh. Credit 4.4: 2 points Alternative Transportation – Parking Capacity Category: Sustainable Sites

33. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 5.1: 1 point Site Development – Protect or Restore Habitat Intent To conserve existing natural area and restore damaged areas to provide habitat and promote biodiversity. Requirements Case #1: Greenfield Sites Case #2: Previously Developed Areas or Graded Sites Potential Technologies & Strategies Greenfield site survey to identify minimal disruption to existing ecosystems and minimize building footprint. Category: Sustainable Sites

34. LEED: Leadership in Energy and Environmental Design GREEN BUILDING STRATEGIES Credit 5.2: 1 point Site Development – Maximize Open Space Credit 6.1: 1 point Stormwater Design – Quality Control (Impervious Surface) Credit 6.2: 1 point Stormwater Design – Quality Control (Stormwater runoff) Credit 7.1: 1 point Heat Island Effect – Nonroof (Site Hardscaping) Credit 7.2: 1 point Heat Island Effect – Roof Credit 8: 1 point Light Pollution Reduction Category: Sustainable Sites

35. Excavation WHAT IS IT: the removal of earth (soil) PURPOSE: the accommodate the construction of a building’s foundation & spaces beneath the surface line WHEN IS IT DONE: after site is cleared of trees (& other debris) and organic soils have been removed

36. Depth of excavation depends on Foundation type (deep or shallow) Soil type Classification of excavations Open: Large and sometimes deep excavations Trenches: Linear excavations for utilities or footings Pits: Excavations for footing of one column, elevator shaft, etc. Excavation

37. Types of Open Excavation BENCHED Excavation Tiered or sloped back Soil will not slide back into hole Steep for cohesive soils Shallow for frictional soils Type is done on large, spacious sites

38. Uniform slope & stepped excavations. Used when adequate space is available on site. Page 518 in textbook Figure 21.8 Two alternatives used for open excavations

39. Types of Open Excavation SHEETED Excavation Temporary vertical wall supports that hold back earth Several methods can be used Sheeting is supported from earth and water pressure Driving into soil enough to act as a cantilever Bracing the sheeting Type is used in urban sites

40. Soldier Beams & Lagging Wide-flanged steel “columns” driven into earth before digging As earth is removed, horizontal wooden planks are placed in between steel “columns” (Lagging) Sheeted Excavation Systems

41. View of excavation: cut faces braced with soldier piles and lagging

42. Connection of lagging to soldier piles Page 522 in textbook Figure 21.16

44. Sheeted Excavation Systems Sheet Piling Vertical planks of material placed against each other to form a solid “wall”; Interlocking vertical steel sheets Material can be wood, steel or precast concrete Material is driven into soil before digging begins Lower part of sheet remains buried, providing cantilever Steel and precast concrete may become apart of the substructure

45. Profile of steel sheet piles Page 519 in textbook Figure 21.9: Steel sheet piles with a Z-shaped profile. Adjacent sections interlock with each other. Several other sectional profiles are available. Figure 21.10: Steel sheet piles being driven into the soil using a diesel pile drive.

46. Sheeted Excavation Systems

47. Bracing Systems Crosslot Bracing Uses vertical and horizontal wide-flanged steel Vertical steel is driven into unexcavated earth As earth is removed, horizontal struts are laid against beams at sheeting face (whalers)

48. Bracing Systems Rakers Diagonal bracing against sheeting wall Rakers are set against whalers and bear against heel blocks Earth removal is challenging because a clamshell bucket has to be used

49. Bracing Systems Tiebacks Like “nailing” into the soil Drill bores hole thru sheeting and into soil Steel cables (tendons) are inserted into holes & filled with grout-substance for anchorage Tendons are stretched tight with hydraulic jacks Tendons are fastened to whalers

50. Section through excavation with soldier piles and lagging Page 521 in textbook Figure 21.13: A section through an excavation supported by soldier piles and lagging. Tiebacks are installed as the excavation proceeds. This is followed by bolting the lagging to solider piles. The number of tiebacks required is a function of the depth of excavation and the type of soil.

51. Drilling for tiebacks Page 521 in textbook Figure 21.14: Drilling of a tieback hole in progress.

52. Close-up: drilling for tiebacks Page 521 in textbook Figure 21.14: Close-up of the same operation. Note that the hole is drilled in the space between the twin C-sections of the piles. The concrete around the sections is lean (weak) to allow easier drilling.

53. Tieback hole Page 522 in textbook Figure 21.15: After the tieback hole has been drilled, a high-strength steel tendon is pushed into the hole and the hole is pressure grouted with concrete.

54. Tendon as tieback Page 522 in textbook Figure 21.15: After the concrete has gained sufficient strength, the tendon is stressed (posttensioned) and then anchored to the pile.

55. Sheeted Excavation Systems Other Sheet Piling Systems Contiguous Bored Concrete Piles (pages 522-523) For when excavation is close to adjacent building Secant Piles (pages 523-524) Modified version of CBP’s using primary and secondary piles

56. Sheeted Excavation Systems Slurry Walls Complicated and expensive procedure Trench is cut out, reinforced and filled with concrete During excavation, to keep the trench from collapsing, benonite clay is pumped into the trench. The clay is displaced and pumped out once the concrete is pumped in

57. Sheeted Excavation Systems Slurry Walls procedure Layout trench by surveying Concrete guide walls are installed Digging begins using a crane-mounted “clamshell” bucket

58. Sheeted Excavation Systems Slurry Walls procedure As trench is dug deeper, a slurry of bentonite clay is poured into the trench

59. Sheeted Excavation Systems Slurry Walls procedure Steel “cage” reinforcement is lowered into trench

60. Sheeted Excavation Systems Slurry Walls procedure Concrete is pumped to the bottom and displaces slurry as concrete fills trench; slurry is pumped out

61. Sheeted Excavation Systems Slurry Walls procedure Slurry is pumped into holding tanks for reuse When concrete has cured, excavation begins As the earth is removed on one side, the trench wall is “tied back” for additional bracing

63. Dewatering When excavation is done below the water table, the site must be “dried-out” 3 Methods Sumps Pumps most common method Well Points Watertight Barrier

64. Well Points Pipe is inserted into earth around excavation site Screen is placed at end of pipe to prevent soil and gravel particles from being pumped with water Pumps are connected to each pipe, where water is sucked through the pipes to bring the water table below excavation level Dewatering

65. Watertight Barrier Used when other substructure of surrounding buildings will be affected by dewatering Slurry wall can be used Strong system of bracing/tiebacks is required Must resist hydrostatic pressure of water Dewatering

66. Next Lecture, Part 2- Foundations