MANUAL FOR GEOTECHNICAL INVESTIGATION AND GEOTECHNICAL DESIGN PART 2: GROUND INVESTIGATION AND GEOTECHNICAL DESIGN DOCUMENT NO: TR-509 SECOND EDITION JUNE-2021 DOCUMENT AMENDMENT PAGE EDITION REVISION DATE PAGE NO. AMENDMENTS NOTES NO. NO. 01 00 DEC 2016 02 01 JUNE TR-509-2: Addition as below: 2021 TABLE-2 In addition to boreholes, the excavated trial pits (PAGE-20) shall be utilized to collect bulk samples from subgrade. CBR and other field/laboratory tests shall be carried out on samples collected at/below subgrade instead of zone planned to be excavated for pavement construction. 02 01 JUNE TR-509-2: Modify as below: 2021 TABLE-2 Low rise buildings (e.g. toll plaza or road (PAGE-21) maintenance depot), shades or other landscaping structures. One exploratory hole at building/structure location 02 01 JUNE TR-509-2: Notes added as below: 2021 TABLE-2 The provided spacing in table-2 are between two (PAGE-22) similar type of exploratory holes and should be finalized in conjunction with the depth requirements provided in Table-3. 02 01 JUNE TR-509-2: Modify as below: 2021 TABLE-3 Low rise buildings (e.g. toll plaza or road (PAGE-25) maintenance depot), shades or other landscaping structures. 02 01 JUNE TR-509-2: Notes added as below: 2021 TABLE-3 It is designer responsibility to ensure that required (PAGE-26) criteria of investigation shall be fulfilled during the design stage. In-case, investigation results may require further additional number of boreholes and/or few boreholes may require to extend up to greater depth, efforts shall be made to execute it during design stage. However, if due to time or other constrains the additional/extended boreholes cannot be executed during design stage along with main investigation, then particular additional scope can be added to verification stage investigation (construction stage). Approval and agreement with authority reviewer shall be required in this regard and design Consultant shall undertake full responsibility of the design, errors and associated risks due to non-compliance to the investigation requirements at design stage (if any). 02 01 JUNE TR-509-2: Addition as below: 2021 TABLE-11 Water Soluble Salts in Soil: BS 1377: Part 3: 1990 (PAGE-43) (Amd. 9028-96), and Earth Manual Des.8: A. Page 1-2 Shall be tested at 0.5m interval for soil above groundwater table and few samples from soil below groundwater table. 02 01 JUNE TR-509-2: Addition as below: 2021 TABLE-13 Total Dissolved Solids (TDS): BS 1377 : Part 3 : 1990: (PAGE-47) Cl: 8. A Adequate frequency below groundwater table. 02 01 JUNE TR-509-2: Notes added as below: 2021 TABLE-14 Where, in-situ/laboratory tests not performed to (PAGE-49) determine modulus of elasticity (Em). For non- cohesive soil a criteria of Em = 1N and for rock stratum a criteria of (Em=J x Mr x UCS) shall be adopted. 02 01 JUNE TR-509-2: Modified as below: 2021 8.1 (PAGE- The recommended analysis is a total stress analysis 85) in which the seismic demand (represented by the earthquake induced stresses) is compared to the seismic capacity (undrained cyclic shear strength of the soil, which is also called liquefaction resistance). The seismic demand will be denoted as CSR (cyclic stress ratio), whereas seismic capacity will be denoted as CRR (cyclic resistance ratio). The safety factor (SF), computed as a ratio between CRR and CSR, should not be less than 1.25. Evaluation of settlements in dry sands due to seismic densification can be carried out using guidance available in Kramer (154). In order to conduct proper assessment of liquefaction potential, investigations of soil characteristics are required in terms of in situ Standard Penetration Tests (SPT) or Cone Penetration Tests (CPT). It is to be noted that CPT data is preferred for assessing potential for liquefaction and seismic densification of loose granular strata during an earthquake event. If soils are found to be susceptible to liquefaction and the ensuing effects are deemed capable of affecting the load bearing capacity or the stability of the foundations/roads/pavement, measures, such as ground improvement and/or pile foundation (structures) shall be taken to ensure stability. The liquefaction hazard may be neglected when one of the following conditions is fulfilled: i) Sands have a clay content greater than 20% with plasticity index (PI) larger than 10. ii) Sands have a silt content greater than 35% and at the same time the SPT normalized blow count value (N1(60)) is larger than 20. Page 1-3 iii) Sands are clean, with SPT normalized blow count value (N1(60)) larger than 30. 02 01 JUNE TR-509-2: Modified as below: 2021 TABLE-26 Methods described in Tomlinson(2) (2001)(102), (PAGE-90) Bowles (1996)(159) and Hong Kong Geoguide 1 (1994)(160). Methods described in Tomlinson(3) (2008) (161). AASHTO LRFD (2017) or Latest Edition/Interim(4) Notes added as below: (2) For Spread footings minimum safety factor of 3.0 shall be adopted to calculate net allowable bearing capacity and total tolerable settlement shall not exceed 25mm. (3) Pile allowable compression capacities based on ASD method shall be calculated by using minimum factor of safety (2.5 for skin friction and 3.0 for end bearing). Tension capacities shall not exceed 70% of allowable compression load. (4) Pile strength design shall comply with LRFD bridge design specifications and guidelines set forth in ADQCC roads structures design manual TR-516. (5) In order to calculate the compression capacity for piles socket in rock, end bearing shall be ignored. 02 01 JUNE TR-509-2: Modified as below: 2021 TABLE-26 Strength, trafficability, requirement of capping, (PAGE-91) settlement/collapses due to low CBR/loose layer underneath or weak subgrade, and/or presence of unsuitable/soluble material below subgrade. 02 01 JUNE TR-509-2: New Section (Ground Improvement & Treatment of 2021 8.5 (PAGE- Voids/Cavities) added: 92) The geotechnical risks and hazards shall be identified in details by performing geophysical/geotechnical investigation at design and verification stage. In case investigation findings indicates “unfavourable” conditions susceptible to liquefaction and/or settlement of roads/pavement/infrastructures/structures/utilities etc. Ground improvement (such as soil replacement, reinforcement with geosynthetics, vibro- compaction or vibro-flotation, vibro replacement (stone columns), dynamic compaction/replacement, CMC columns (controlled modulus columns/rigid inclusions), Rapid Impact Compaction (RIC), High Energy Impact Compaction (HEIC), soil mixing or other applicable techniques) shall be performed prior to construction over it. The conventional ground improvement techniques listed above are for general guidelines and should be finalize at site by Ground Improvement Specialist in function of the soil type (gradation and density) and the site trials results, in order to efficiently satisfy the performance criteria. Page 1-4 An indicative plan showing the location of the proposed improvement techniques shall be prepared based on the findings of the existing and complementary subsurface investigation data at the project design stage. The following performance requirements shall be followed as guideline (post improvement); 02 01 JUNE TR-509-2: New sub section added as below: 2021 8.5.1 Minimum Criteria for Roads/Pavement: (PAGE-92) i) Total settlement (immediate and long- term) shall not exceed 25mm at 100% design load and shall not be considered less than 40 kN/m2 (considering vehicle load of HL-93). ii) The safety factor against liquefaction shall not be less than 1.25. iii) The in-situ CBR of improved ground shall not be less than CBR value adopted in design and in general shall not be less than 10% at 5mm penetration for any condition. 02 01 JUNE TR-509-2: New sub section added as below: 2021 8.5.2 Minimum Criteria for (PAGE-93) Structures/Infrastructures/Utilities Foundation: i) Total settlement (immediate and long- term) shall not exceed 25mm (footings) and 50mm (Raft) at 100% of design load. ii) The safety factor against liquefaction shall not be less than 1.25. iii) The post-improvement vertical and lateral settlements induced by earthquake loading shall be limited to a maximum of 20 mm at the top of the ground. iv) Angular distortion (differential settlement) of points 5m apart shall be less than 1:500. v) A minimum equivalent Young’s Elastic Modulus for the treated ground of 30MPa. vi) SPT: Minimum N value of 30 along the improved depth of granular material. vii) CPT: Minimum cone tip resistance value of 10 MPa along the improved depth of granular material. viii) Minimum relative density of 70%. ix) An effective angle of shear resistance not less than 35° for the medium dense to dense sand (granular material). The parameters of each locality must be checked for the material type, mineralogy, size, and for the deposit thickness before the final decision to be made on the improvement method, level of energy used, and spacing of improvement points. Moreover, the thickness of the soil cover, which is important in determining the improvement method, can be checked through the pre-CPT/SPT testing with close spacing. It shall be noted that vibrations Page 1-5 induced by heavy machinery shall be limited, while working next to existing structures or utilities that are sensitive to vibrations. The efficiency of the final adopted improvement method for the project, final thickness/depth of the improvement ground and verification of set performance criteria shall be checked by performing post ground improvement in- situ tests (SPT, CPT, Plate load test (PLT), Zone Load test, CBR etc.). The suitability of the soil material shall be determined by performing standard laboratory tests (such as gradation, plasticity index (P.I), proctor, CBR, organic content, water soluble salts (WSS), total dissolved salts (TDS), sulphate, chloride, pH and/or other.) by testing collected soil samples as per the standard requirements provided under TR-542 (part-1 & 2).