Soil and Earth Works Faculty of Applied Engineering and Urban Planning Civil Engineering Department Lecture 3 - Week 2 2 nd Semester 2008/2009 UP Copyrights 2008 Introduction to construction Industry

Content Excavation Slope Support

Excavation Work Excavation is the changing of the natural of the soil. Excavation work can be done in:  Dams work.  Land improvement works.  Roads and airports works.  Construction works.  Laying out of electricity, telephone, pipelines works...etc. The construction excavations has three forms: 1.Site mobilization. 2.Excavation work to required level. 3.Backfilling, leveling and compaction works. Note : Excavations can be deep or surface (shallow)

Excavation Work Excavation classification due to the type of soil:  Excavations on sand.  Excavations on rocks.  Excavations on a mix soil (sand and rock). Excavations methods:  Mechanical Excavations.  Manual Excavations.  Excavations by detonation.

Excavations can be classified according to: 1. Soil type: 1.1 Coarse grained soil (cohesive less soil) diameter > mm (Gravel زلط, sand رمل ….etc) 1.2 Fine grained soil (cohesive soil)- diameter < mm (Clay طين, silt طمي, …etc ). 1.3 rock soil. 1. Slope on cohesive less soil: Slope of excavation depend on internal fraction angle as follow:  In cohesive less soil safe slope <= internal fraction angle.  Excavation under water level safe slope <= 60% of internal fraction angle. Excavation classifications

Some practical considerations Fencing Provide perimeter rigid frame fencing. Ramp A ramp has to be designed to insure ease of access of excavation and transport machines. Disposal and Stockpiling Within site or outside it. Slope Support Will be elaborated later in this lecture. Excavation Site

Questions?!

In good soil conditions and with shallow foundations, the excavation consists of scraping and stockpiling the organic topsoil. This topsoil will be valuable for all the landscaping needs of the finished project. The good sub-grade material is also scraped and stockpiled to create a compacted mat, or leveling pad, upon which is built the structure’s foundations. Excavation must provide a natural slope so that rain or seepage will drain the water to a corner of the site, where it can be disposed of through pumps. In poor surface soils, deeper excavations may be required to reach a stratum which has adequate bearing capacity. Otherwise, deep foundations (more expensive) may be required. Excavation

Common Excavation and Backfill Problems. 1.Unforeseen and differing conditions, such as a higher water table than predicted; unexpected large rock masses, or large boulders; unsuitable materials (undetected garbage pits, old foundations, abandoned utilities, etc.). 2.Weather. The site must have access at all times. Therefore, the contractor may have to maintain all-weather roads. Borrow pits must also be used in all weather conditions. 3.Variable excavation volumes. Every site has some amount excavation. Excavation

Units of Measure: for excavation and backfill: cubic meter for grading: square meter Major Productivity Issues: Type of operation (large sites versus confined spaces) Type of soil conditions (from the best – rock to the worst - clays) Transportation of fill (large distance to borrow pit, or moving within the site) Expected Environmental Conditions (cold winters, hot summers, labor problems) Excavation

Questions?!

Slopes: 1.An unrestricted site (site is sufficiently larger that the building footprint) Create a bench or/ and angle of repose استناد for the excavation, with a perimeter clearance. Prevent bank erosion تآكل, divert rain water, preserve safety and store backfill. This is the most common site condition and the least expensive. 2.A restricted site (the site is very limited and access is constricted) Slope Support

The angle of repose is the maximum angle of a stable slope determined by:  friction,  cohesion,  and the shapes of the particles. Angle of Repose

Protection for Restricted Site 1.Driven Steel, Plastic, Wood or Concrete Sheeting. a)Soldier piles and wood lagging b)Steel sheet piling c)Wood sheet piling d)Pre-cast concrete sheet piling 2.Placed (in-situ) Walls. a)Cement Walls b)Soil-cement (soil-mix) walls Slope Support

Questions?!

Support of Trenches خندق a)Slurry Walls b)Bracing Slope Support

Slurry Wall

Braced Cuts