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Soil and rock classification shall be based on materials disclosed by borings, test pits or other subsurface exploration methods. Soil classifications shall be determined in accordance with ASTM D 2487 (refer to Table 1803.3) and the supplemental definitions contained herein. Rock classifications shall be determined in accordance with generally accepted engineering practice and the supplemental definitions contained herein. Laboratory tests shall be conducted to ascertain these classifications where deemed necessary by the engineer responsible for the geotechnical investigation or the commissioner.

BEDROCK.
  1. Hard sound rock (Class 1a). Includes crystalline rocks, such as gneiss, granite, diabase and mica schist. Characteristics are as follows: the rock rings when struck with pick or bar; the rock does not disintegrate after exposure to air or water; the rock breaks with sharp fresh fracture; cracks are unweathered, less than 1/8-inch (3.2 mm) wide, and generally no closer than 3 feet (914.4 mm) apart; and the RQD (rock quality designation) with a double tube, NX-size diamond core barrel is generally 85 percent or greater for each 5-foot (1524 mm) run; or core recovery with BX-size core is generally 85 percent or greater for each 5-foot (1524 mm) run.
  2. Medium hard rock (Class 1b). Includes crystalline rocks of paragraph 1 of this subdivision, plus marble and serpentinite. Characteristics are as follows: all those listed in paragraph 1 of this subdivision, except that cracks may be 1/4-inch (6.4 mm) wide and slightly weathered, generally spaced no closer than 2 feet (609.6 mm) apart; and the RQD with a double tube, NX-size diamond core barrel is generally between 50 and 85 percent for each 5-foot (1524 mm) run; or core recovery with BX-size core is generally 50 to 85 percent for each 5-foot (1524 mm) run.
  3. Intermediate rock (Class 1c). Includes rocks described in paragraphs 1 and 2 of this subdivision, plus cemented shales and sandstone. Characteristics are as follows: the rock gives dull sound when struck with pick or bar; does not disintegrate after exposure to air or water; broken pieces may show moderately weathered surfaces; may contain fracture and moderately weathered zones up to 1 inch (25.4 mm) wide spaced as close as 1 foot (304.8 mm) apart; and the RQD with a double tube, NX-size diamond core barrel is generally 35 to 50 percent for each 5-foot (1524 mm) run; or a core recovery with BX-size core of generally 35 to 50 percent for each 5-foot (1524 mm) run.
  4. Soft rock (Class 1d). Includes rocks described in paragraphs 1, 2, and 3 of this subdivision in highly weathered condition, plus talc schist and poorly cemented shales and sandstones. Characteristics are: rock may soften on exposure to air or water; may contain highly weathered zones up to 3 inches (76.2 mm) wide but filled with stiff soil; and either the RQD with a double tube, NX-size diamond core barrel is less than 35 percent for each 5-foot (1524 mm) run or core recovery with BX-size core of generally less than 35 percent for each 5-foot (1524 mm) run, or a value of N60 greater than 50 blows per foot (0.3 meters).

SANDY GRAVEL AND GRAVELS. Consists of coarse-grained material with more than half of the coarse fraction larger than the #4 size sieve and contains little or no fines (GW and GP). The density of these materials shall be determined in accordance with the following:
Dense (Class 2a). These materials have a value of N60 greater than 30 blows per 1 foot (0.3 meter).

Medium (Class 2b). These materials have a value of N60 between 10 and 30 blows per 1 foot (0.3 meter).

Loose (Class 6). These materials have a value of N60 less than 10 blows per 1 foot (0.3 meter). These materials shall be considered nominally unsatisfactory bearing materials.

GRANULAR SOILS. These materials are coarse-grained soils consisting of gravel and/or sand with appreciable amounts of fines and gravel. Soil types include GM, GC, SW, SP, SM and SC. The density of granular materials shall be determined in accordance with the following:
Dense (Class 3a). These materials have a value of N60 greater than 30 blows per 1 foot (0.3 meter).

Medium (Class 3b). These materials have a value of N60 between 10 and 30 blows per 1 foot (0.3 meter).

Loose (Class 6). These materials have a value of N60 less than 10 blows per 1 foot (0.3 meter). These materials shall be considered nominally unsatisfactory bearing materials.

CLAYS. For soil types SC, CL and CH in the absence of sufficient laboratory data, the consistency of clay materials shall be determined in accordance with the following:
Hard (Class 4a). Clay requiring picking for removal, a fresh sample of which cannot be molded by pressure of the fingers; or having an unconfined compressive strength in excess of 4 TSF (383 kPa); or having a value of N60 greater than 30 blows per 1 foot (0.3 meter).

Stiff (Class 4b). Clay that can be removed by spading, a fresh sample of which requires substantial pressure of the fingers to create an indentation; or having an unconfined compressive strength of between 1 TSF (95.8 kPa) and 4 TSF (383 kPa); or having a value of N60 between 8 and 30 blows per 1 foot (0.3 meter).

Medium (Class 4c). Clay that can be removed by spading, a fresh sample of which can be molded by substantial pressure of the fingers; or having an unconfined compressive strength of between 0.5 TSF (47.9 kPa) and 1 TSF (95.8 kPa); or having a value of N60 between 4 and 8 blows per 1 foot (0.3 meter).

Soft (Class 6). Clay, a fresh sample of which can be molded with slight pressure of the fingers; or having an unconfined compressive strength of less than 0.5 TSF (47.9 kPa); or having a value of N60 less than 4 blows per 1 foot (0.3 meter). This material shall be considered nominally unsatisfactory bearing material.

SILTS AND CLAYEY SILTS. For soil types ML and MH in the absence of sufficient laboratory data, the consistency of silt materials shall be determined in accordance with the following:
Dense (Class 5a). Silt with a standard penetration test where the value of N60 greater than 30 blows per 1 foot (0.3 meter).

Medium (Class 5b). Silt with a standard penetration test where the value of N60 between 10 and 30 blows per 1 foot (0.3 meter).

Loose (Class 6). Silt with a standard penetration test where the value of N60 fewer than 10 blows per 1 foot (0.3 meters). This material shall be considered nominally unsatisfactory bearing material.

TABLE 1803.3
UNIFIED SOIL CLASSIFICATION (Including Identification and Description)

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