- Boulder apron placed with and while not wire mesh gabions.
Stone/boulder pitching (riprap) on slopes, placed by hand with filter layer.
Materials for Riprap
- Stone for apron and pitching shall be sound, hard, durable, and fairly regular in form with a minimum of one facet broken. Stone subject to marked deterioration by water or weather shall not be used.
All stone shall be taken from approved sources. The stones shall be fine boulders or rock, production of granite, quartzite, or similar materials having a selected gravity of a minimum of two.4 and a compressive strength of a minimum of four00 kg/cm2
Stones for apron and pitching shall weigh a minimum of forty weight unit. Spalls shall be minimum twenty five millimetre size and appropriate to fill voids in apron and pitching.
The material for filters shall comprises sound gravel, stone or brick ballast and coarse sand, For one layer filter the compacted thickness of the filter shall not be but one hundred fifty millimetre. For a multi layer filter, the compacted thickness of every layer filter material shall not be but a hundred and fifteen millimetre.
Gabions and city Mattresses
The iron wire shall fulfil the specification of IS 280 or bachelor’s degree 443.
The Minimum weight of metallic element coating per unit space of uncoated wire surface shall be as given below:
Nominal diameter of wire (mm) 2.2 2.7 3.0 3.4 3.9
Nominal weight of coating gm/cm2 240 260 275 275 290
The lastingness of the wire shall be between 40-55 kg/mm2
Gabions shall comprises wire netting double knotted to create a sq. mesh of a hundred millimetre x a hundred millimetre and therefore the stone for filling gabions shall be onerous clean stone between ten cm and twenty five cm. The gauge of the GI wire are ten SWG or as nominal. The gauge if GI wire used as Selvedge wire are of seven SWG.
Box gabions shall have wire frames firmly tied to the netting at the sides of the box. Before inserting any orders for gabion baskets, the Contractor shall submit for the Employer’s Representative’s approval, full details of the hampers he proposes to use.
Apron for Riprap
This work shall comprises egg laying boulders directly, or in wire crates on the bed of rivers or where directed by the Employer’s Representative for cover against scour. The thickness and form of aprons shall be as indicated on the drawings or as set by the Employer’s Representative. The surface on that the apron is to be arranged shall be levelled and ready for the length and breadth as shown on the drawings.
A. Laying Boulder Apron:
To ensure regular and orderly disposition of the total meant amount of stone within the apron, guide walls in masonry shall be engineered a few meter thick and to the total height of the desired thickness of the apron at intervals of thirty meters right along the length and dimension of the apron. at intervals these walls, the stone then shall be hand-packed.
Laying Wire Mesh Gabions within the Apron:
Before putting in position, the gabions shall be stretched to their full size and shall be wired the least bit edges.
Each row of gabions shall be wired to the neighboring row at the highest and bottom edges and at the corners.
Each gabion shall be fastidiously packed by hand with stone thus placed on minimize voids. the highest layers of stones shall be placed with their flattest sides upmost to supply a swish surface for putting the lid. The gabions shall be stuffed twenty five metric linear unit on top of the highest so the lid may be tightly stretched over the stone. The lid shall be wired all spherical.
Adjoining rows of gabions shall initial be half stuffed to confirm that the perimeters of the mesh don’t bulge.
Care should be taken that the gabions don’t seem to be distorted throughout filling.
Gabions and mattresses shall be placed on prime of a filter material. In no case can or not it’s allowed to position gabions and mattresses directly connected with the soil.
Pitching on Slopes and riprap
This work shall contains covering the slopes of guide banks, embankments and where directed by the Employer’s Representative, with stone, boulders or bricks over a layer of granular material referred to as filter to empty off oozing water and to stop erosion of the bottom materials by providing hierarchical material. The pitching shall extend from the most water level, together with allowance for wave action, if any, down and concerning thirty cm below the bed level or as per the drawings. The thickness of pitching shall be provided as shown on the drawings.
- Before birthing the pitching, the perimeters of banks shall be cut to the specified slope profile place up by suggests that of lines and pegs at intervals of three metres to make sure regular straight work and an even slope throughout. Depressions shall be stuffed and totally compacted.
The filter granular material is to be arranged over the ready base and befittingly compacted to a thickness of a hundred and fifty metric linear unit or as nominal on the drawings.
The lowest course of pitching shall be started from the toe wall and build up in courses upwards. The toe shall be in dry rubbish masonry (uncoursed).
The stone/boulder pitching shall begin during a trench below the toe of the slope. Stone shall be placed by derrick or by hand to the specified length, thickness and depth conformist to the Drawings. Stone shall be set traditional to the slope and placed in order that the massive dimension is perpendicular to the face of the slope unless such dimension is bigger than the desired thickness of pitching. the biggest stone shall be placed within the bottom courses and to be used as headers for succeeding courses.
When full depth or pitching may be shaped with one stone, the stones shall be arranged breaking joints and every one interstices between adjacent stones shall be stuffed in with spalls of the correct size and compact in with hammers to make sure tight packing.
When there square measure 2 or additional layers the stones should be arranged to get the look thickness of pitching, masonry shall be used and stones shall be guaranteed.
Measurement and Payment
Measurement: The protection works shall be measured as set forth below:
If directed by the Employer’s Representative for measuring the materials could ought to be stacked at website before birthing and zip further are going to be paid to the Contractor for this stacking.
The wire mesh gabions (boulders and wire crates) are going to be measured in cube-shaped meters.
The filter and stone/boulder pitching (riprap) are going to be measured on an individual basis in cube-shaped meters for every category of fabric.
Preparation of base for birthing the flooring shall be deemed related to the work.
For birthing apron, excavation up to a mean depth of fifteen cm shall be deemed to be enclosed within the main item and shall not be measured on an individual basis unless otherwise nominal.
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