Mississippi Excavation and Grading

T-99 compacts the sample in three layers struck 25 times with a 5.5-lb hammer for a total effort of 12,400 ft-lb and is usually specified under building slabs, sidewalks and utility trenches under grassy areas, while T-180 uses five layers struck 25 times with a 10-lb hammer for 56,250 ft-lb and is used for higher design loads such as federal highways, airport runways and nuclear power plants.

Type A is cohesive soil with an unconfined compressive strength of 1.5 tsf (144 kPa) or greater (cemented soils such as caliche and hardpan qualify), but no soil is Type A if it is fissured, previously disturbed, or subject to vibration from heavy traffic or pile driving; soil meeting Type A strength that is fissured or subject to vibration is reclassified as Type B, which is cohesive soil greater than 0.5 tsf but less than 1.5 tsf.

Type B cohesive soil has an unconfined compressive strength greater than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa); Type C cohesive soil is 0.5 tsf (48 kPa) or less.

In the drying test a sample that develops cracks as it dries indicates significant fissures (fissured cohesive), a sample that dries without cracking and requires considerable force to break by hand is unfissured cohesive (then determine unconfined compressive strength), and a sample that pulverizes easily is granular.

The plan view is a bird's-eye overhead view showing the layout of the work area, while the profile view is a horizontal cut-away (cross-section) along the alignment showing elevations, grades and depths.

Direct construction costs are the labor, material and equipment tied to a specific trade or phase (pipe materials, backhoe rental, pipe bedding aggregate), while direct (job) overhead costs result from taking a particular job but are not tied to a trade or phase — such as traffic control (barricades, flaggers, lane delineators) and pipe/soil density testing.

Igneous rock formed from cooled magma is homogeneous with few planes of weakness and is therefore difficult to rip, while sedimentary rock is formed from compacted layers of material deposits, is the most abundant exposed rock on Earth's surface, and responds better to ripping.

A scraper can dump its payload in uniformly thick layers, which trucks cannot do, improving compaction productivity on embankment construction.

Water settling is most effective in sand, gravel and desert-type soils, which drain quickly and can be worked while still quite wet, but least effective in cohesive silt and clay, which take a long time to drain.

Sheepsfoot ideal output uses width × speed × compacted lift thickness × 16.3 ÷ passes, corrected by 0.83 job efficiency and 0.9 operator ability; hoe-mounted plate ideal output uses plate area (sf) × lift thickness (ft) × cycles per hour ÷ 27, corrected by 0.83 job efficiency and 0.8 operator ability.

At wells, pits, shafts and similar excavations 6 feet or more deep, guardrail systems, fences, barricades or covers are required regardless of visibility; at general excavation edges 6 feet or more deep, guardrail systems, fences or barricades are required only when the excavation is not readily seen because of plant growth or other visual barrier.

The Cross Section Method averages the cut or fill depths at a prism's four corners and multiplies by the prism area, while the Average End Area Method is used where a single prism contains both cut and fill — the prism is split at the zero line and the cut and fill sections are calculated separately.