Name of Work:- Borehole drilling and Sensor installation as part of implementing Landslide Early Warning System
Sl. No.
Item Description
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\\" Drilling borehole and installing borehole sensors as part of implementing Landslide Early Warning Sytem \\"
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Borehole is to be made at a minimum seven (07) locations. Locations will be provided on the site map separately. Drilling is to be carried out as per IS 1892: 2021 through 100 mm/125 mm nominal diameter boreholes. ABS casing is to be provided throughout the depth of the drilled hole. Maximum borehole depth to be drilled is 210 m with varying depth from the existing ground level and up to a depth of 2m into the bedrock (unweathered bedrock). Number of boreholes may vary based on achieving the required depth. A percussion or rotary core drilling method is to be used for borehole excavation. The boring includes the drilling in overburden material. However, if bedrock is encountered, the drilling is to be carried out further 2 m into the unweathered bedrock. The amount will be released as per Actuals.
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Once the hard stratum (rock) is met with (hard stratum is confirmed by geologist/site in-charge), further drilling is to be carried out by HX core drilling with TC/Diamond bits as per IS 6926: 1996 (RA 2020) by using double core/triple core barrel up to 2 m into the bedrock. Each run of the core drilling is to be properly recorded with core logging. At the end of each run, the drill rod string with the core barrel is to be extracted and the core is to be recovered.The cores are to be carefully transferred to the core boxes and properly preserved, numbered, labelled, and photographed for reporting purposes. The rock core recovery (C.R.) percentage and Rock Quality Designation (RQD) are to be recorded. Some of the cores are to be sent to the laboratory for determining density and specific gravity of rock (IS 13030: 1991, RA 2021), uniaxial compressive strength (UCS) of rock samples of NX size (IS 9143: 1979, RA 2021), determination of shear strength of rock materials in triaxial compression as per IS 13047: 1991(Reaffirmed Year: 2021). The amount will be released as per Actuals.
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ABS casing pipe diameter 70 mm, Casing pipes should be along the complete drill length of the borehole having precision-machined threaded ends (V-threads or trapezoidal threads) or quick-joint (QJ) flush couplings, ensuring a watertight, self-aligning connection without the need for solvent cement. Top ABS caps (at least 10 nos.) to fit 70 mm OD & Bottom ABS casing caps (at least 10 nos.) to fit 70 mm OD. Joints may be sealed using Mastic tape. Size 50 mm/100 mm width along with BOPP Waterproofing ceiling tape, having size 50 mm/100 mm width.
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A slotted ABS casing/pipe is to be provided at the bottom of the target depth. Geosynthetic wrapping is to be provided, and the side wall is to be filled with clean, washed sand filter (0.5–2 mm size) around the slotted portion, with a thickness of 300–600 mm above and below the screen. Bentonite pellets or bentonite-cement grout plug is to be provided above the sand filter, having a thickness of 300–500 mm. Backfilling is to be done for the rest of the borehole with grout/bentonite. (optional) The amount will be released as per Actuals.
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210 m long guiding rod of Aluminium having a diameter of 25 mm for the fixity of various sensors The amount will be released as per Actuals.
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Testing
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To conduct standard penetration tests (SPTs) as per IS 2131: 1981(RA 2021) in the boreholes and to collect disturbed soil samples from boreholes at 1.5 m interval in depth or when there is a change in strata, whichever is earlier. From the boreholes, undisturbed samples are to be collected using a Shelby tube of 75 mm diameter and 450 mm long, and disturbed samples to be collected using an SPT sampler at a vertical interval of 1.5 m or from depth at which change in stratum occurred earlier. Collecting undisturbed soil samples at regular intervals and at every identifiable change of strata to supplement the boring records. Recording the depth of the groundwater table in all the bore holes, if observed up to the depth of exploration during boring work. Groundwater accumulation in boreholes is to be monitored during and after completion of drilling activities.Determination of field moisture equivalent as per the IS 2720: Part 18: 1992(Reaffirmed Year: 2021).Conducting the following laboratory tests on selected disturbed / undisturbed soil samples collected from various bore holes / test locations: bulk and dry density, specific gravity (IS 2720 : Part 3 : Sec 1& 2 : 1980 Reaffirmed Year: 2021), water or moisture content (IS 2720: Part 2: 1973Reaffirmed Year : 2020), grain size analysis including hydrometer analysis (as per IS 2720 : Part 4 : 1985Reaffirmed Year : 2020) and, determination of liquid limit and plastic limit (IS 2720: Part 5: 1985Reaffirmed Year : 2020), laboratory determination of permeability of soil (IS 2720: Part 17:1986Reaffirmed Year: 2021) or granular soils (IS 2720: Part 36: 1987Reaffirmed Year:2021), classification and identification of soils for general engineering purposes(IS 1498: 1970Reaffirmed Year: 2021), tri-axial shear tests in unconsolidated undrained condition (IS 2720: Part 11: 1993Reaffirmed Year: 2021), direct shear tests (IS 2720: Part 13: 1986 Reaffirmed Year : 2021 or IS 2720 : Part 39: Sec 1: 1977Reaffirmed Year: 2021), consolidation test (IS 2720: Part 15: 1965 Reaffirmed Year: 2021). All these tests to be conducted as per the IS code guidelines. The amount will be released as per Actuals. Please Enable Macros to View BoQ information
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