The capping layer shall comprise approved imported material complying with the limits shown in Table 20.3.5B. TABLE 20.3.5B: Plasticity Index Limits of Grading Plasticity x % passing 0.425 Physical Properties (% Passing) After Compaction After Compaction mm after compaction Sieve Size AS (mm) (max) (max.) CBR Swell 75.0 4.75 0.075 (min) (max) (max) 1000 25 % % m/sec 8 1.5 1x10-9 100 60 - 80 10 - 40 Note: CBR and Swell values are to be determined on specimens obtained from fraction of material passing 19.0mm sieve, compacted at optimum moisture content and 98% of maximum dry density as determined by test Standard Compactive effort, and soaked for 4 days prior to testing for CBR and Swell. The Permeability value is to be determined on specimens obtained from that fraction of material which passes a 19.0mm AS sieve, compacted at optimum moisture content and 98% of maximum dry density as determined by testing using Standard Compactive effort as for CBR and Swell. Treatment of Unstable or Wet Subgrades If the clay subgrade is in a saturated with moisture content in excess of the optimum, and rolling of the subgrade is not possible, the Contractor shall advise the Superintendent. Subject to the approval of the Superintendent and depending upon the prevailing weather conditions lime stabilisation below the base level may be substituted to improve the subgrade. Where the subgrade clay contains excessive basalt boulders and stabilisation is not practicable the saturated clay shall be removed and replaced with approved filling in accordance with VicRoads standard specification Section 204 Earthworks Clause 204.10 (current issue). – TREATMENT OF ROCKY SUBGRADE Unless otherwise specified, where the excavation at base level is rocky material or contains excessive basalt boulders, the subgrade shall be loosened and rocks or boulders removed to the following depths in all areas on which pavement is to be placed: Bedrock minimum of 150mm below base level – Loose rock and boulders minimum 300 mm below base level – Any resulting depressions be backfilled with Type A material of low permeability complying with Table 20.3.5B. Such backfilling, together with the remaining loosened material, shall be reworked and compacted as specified.
The capping layer shall comprise approved imported material complying with the limits shown in Table 20.3.5B. TABLE 20.3.5B: Physical Properties Limits of Grading (% Passing) After Compaction Sieve Size AS (mm) Plasticity Index x % passing 0.425 mm after compaction (max.) Plasticity After Compaction (max) CBR (min) % Swell (max) % (max) m/sec 75.0 4.75 0.075 1000 25 8 1.5 1x10-9 100 60 - 80 10 - 40 Note: CBR and Swell values are to be determined on specimens obtained from fraction of material passing 19.0mm sieve, compacted at optimum moisture content and 98% of maximum dry density as determined by test Standard Compactive effort, and soaked for 4 days prior to testing for CBR and Swell. The Permeability value is to be determined on specimens obtained from that fraction of material which passes a 19.0mm AS sieve, compacted at optimum moisture content and 98% of maximum dry density as determined by testing using Standard Compactive effort as for CBR and Swell. Treatment of Unstable or Wet Subgrades If the clay subgrade is in a saturated with moisture content in excess of the optimum, and rolling of the subgrade is not possible, the Contractor shall advise the Superintendent. Subject to the approval of the Superintendent and depending upon the prevailing weather conditions lime stabilisation below the base level may be substituted to improve the subgrade. Where the subgrade clay contains excessive basalt boulders and stabilisation is not practicable the saturated clay shall be removed and replaced with approved filling in accordance with VicRoads standard specification Section 204 – Earthworks Clause 204.10 (current issue). TREATMENT OF ROCKY SUBGRADE Unless otherwise specified, where the excavation at base level is rocky material or contains excessive basalt boulders, the subgrade shall be loosened and rocks or boulders removed to the following depths in all areas on which pavement is to be placed: Bedrock – minimum of 150mm below base level Loose rock and boulders – minimum 300 mm below base level Any resulting depressions be backfilled with Type A material of low permeability complying with Table 20.3.5B. Such backfilling, together with the remaining loosened material, shall be reworked and compacted as specified.
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