Environmental Management Plan GMS Ben Luc Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 METHOD STATEMENT OF SLOPE PROTECTION TABLE OF CONTENTS I SLOPE PROTECTION II GRASS[.]
GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 METHOD STATEMENT OF SLOPE PROTECTION PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 TABLE OF CONTENTS I SLOPE PROTECTION II GRASSING OF SLOPES III GRABIONS PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 I SLOPE PROTECTION General Unless otherwise specified riprap and concrete slope protection shall always be constructed as an impervious layer upon designated surfaces and shall have mortared joints Reinforced concrete drain chutes, unless otherwise specified, shall be constructed where curb and gutter is used with embankment heights greater than metres to safely convey surface runoff down the embankment slope The drain chutes shall connect the drop openings integrated into the curb with the toe of the slope The curb and gutter installation shall be placed along each shoulder edge when the roadway is in a normal cross section and only along the lower edge in a superelevated section Spacing of drain chutes shall be as indicated on the Drawings or as directed by the Engineer Grouted riprap protection shall also be placed at the toe of the drain chute as detailed in the Drawings Reinforced concrete drain outlets, unless otherwise specified, shall be constructed along the side slopes between the outlet of pipe culverts and the toe of embankment to guard against erosion wherever the vertical distance between the pipe outlet and toe of slope is declared critical by the Engineer The drain outlet shall be a trapezoidal reinforced concrete gutter of a type as detailed in the Drawings Grouted riprap protection shall be integrated into the discharging end of each drain outlet as detailed in the Drawings Concrete interceptor ditches, unless otherwise specified, shall be constructed at the toe of benches where depths of excavation exceed metres and the subgrade material is subject to erosion Interceptor ditch linings may be reinforced concrete or plain concrete and shall be as detailed in the Drawings or as directed by the Engineer Concrete, riprap or sacked concrete embankment slope protection shall be constructed at locations shown on the drawings or as directed by the Engineer This type of slope protection shall generally be used where embankment intrude into streams or watercourses All riprap and concrete slope protection shall conform to the dimensions and requirements shown on the Drawings, these Specifications or as directed by the Engineer Preparation When newly constructed earthworks are to be provided with riprap or slope protection, the excavation or embankment shall be constructed to the planned profiles and dimensions, without making allowance for the space to be occupied by the protection works Excavation for protection works will only be carried out immediately prior to its construction The Contractor shall obtain the approval of the Engineer to his proposed PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 method of construction prior to commencement of construction of the section of the works concerned The areas to be covered shall, at the proper time, be laid out to intended positions, and all necessary cut and fill stakes, batter boards and construction lines set up Every effort shall be made to have the surfaces in such condition as to require solely excavation immediately prior to the laying of the materials Where, however, low areas are encountered they shall be backfilled and thoroughly tamped at the earliest practical time in advance of the laying of masonry, to avoid settlement after placing materials It is not necessary that the entire area to be protected be excavated and fine graded in advance of the laying, work should be always laid upon a freshly excavated and stable surface Aggregates and cement for sacked concrete slope protection shall be mixed dry, by hand, or mechanically in the proportion of 1:10 (cement aggregate) measured by volume until the mixture is uniform in colour Aggregates shall meet the gradation and quality requirements as specified in the Drawings The mixture shall be placed into the sacks and filled approximately 75% full, and shall be securely and substantially sewed, the ends forming a straight edge The sacks when filled shall have an average thickness or depth of 200 mm Cut off Wall or Sheeting Riprap and concrete slope protection will usually be accompanied by a bottom cutoff wall Where the cutoff wall is composed of masonry, a trench shall be excavated to the dimensions required for the masonry, dewatered, and the masonry placed directly in the trench, visually without any form Where the cutoff wall is composed of sheeting, care shall be taken not to disturb, by excavation or otherwise, any natural ground, stream beds or other formations intended to be in front of the sheeting After laying has been completed, backfilling shall be carried out around the edges and mechanically tamped Special care shall be given to backfilling and compacting any spaces or volumes resulting from the removal of forms If the bottom of the riprap or concrete slope protection does not occur In rock or other natural strata accepted as non-erodible, riprap shall always be founded or sealed on the bottom with appropriate cutoff trenches or sheeting For cutoff walls composed of masonry, the prepared trench shall be dewatered and completely filled with stones and mortar The trench shall first be filled approximately 60 per cent with mortar and immediately thereafter stones shall be dropped and pushed into the unset mortar or concrete so as to make a solid, dense masonry wall Additional mortar or concrete may be added to the top so as to obtain a screeded, level top surface Only such length of french is to be worked upon at a time as to insure that all stones can be inserted in fresh concrete Where the foundation under the riprap or concrete slope protection is unstable and the masonry cutoff may settle or fail, the cutoff masonry will be omitted and sheeting as required shall be driven The cutoff masonry and/or sheeting shall be constructed before laying the riprap or concrete slope protection PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Where the cut-off wall is composed of sacked concrete and after laying and backfilling has been completed, the sacked concrete shall be thoroughly soaked by spraying with water to the satisfaction of the Engineer The cut-off protection shall be constructed before laying the sacked concrete slope protection After cutoff masonry or sheeting has been placed and accepted the laying of slope protection shall be commenced in tight contact with the cutoff masonry or sheeting and laid from the bottom towards the top Stone and precast concrete blocks shall be laid in close contact Placing Riprap Stones placed below water line shall be distributed so that the minimum thickness of the riprap is not less than that specified Stones above the water line shall be placed by hand They shall be laid with close, broken joints and shall be firmly bedded into the slope and against the adjoining stones The stones shall be laid perpendicular to the slope with ends in contact The riprap shall be thoroughly compacted as construction progresses and he finished stones shall present an even, tight surface Interstices between stones shall be chinked with spalls firmly rammed into place Unless otherwise provided, riprap shall have the following minimum thicknesses, measured perpendicular to the slope: - Class A: 300 mm; - Class B: 450 mm; - Class C: 600 mm The surface of riprap placed above the water line shall not vary from the theoretical surface by more than 80 mm at any point Loose Riprap Loose riprap where specified on the drawings shall be placed by dumping and spreading in layers by a mechanical device or other methods approved by the Engineer, all to a secure, stable mass Surface irregularities of the slope shall not vary more than 100mm along the intended slope After completion and approval of the riprap placement, the surface voids of the riprap in the footing ừench and on the lower portions of the slope shall be filled with excavated material and dressed to the satisfaction of the Engineer Grouted Riprap Riprap shall be arranged in such a way that the largest rocks are at the bottom of the slope The surfaces of the rock shall be cleaned of adhering dirt and clay and shall be moistened Rocks in the bottom courses and to a vertical height and thickness as shown on the drawings, or where directed by the Engineer shall be carefully arranged by hand to interlock and form a three-point bearing on the underlying rocks with their longitudinal axis normal to the embankment face PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 As each of the larger stones is placed it shall be surrounded by fresh mortar and adjacent stones shall be pushed into contact In the case of grouted riprap, the interstices may be partly filled with spalls or small stones, and finally ail remaining joints or openings filled solidly with mortar Where the pieces are composed of precast concrete, they shall be laid with broken joints As each course is laid, the top of the joint shall be filled with mortar so that the succeeding course can be shoved into position in a full bed of mortar At the conclusion of a course to the specified levels all excess mortar forced up shall be spread uniformly to completely fill all surface voids All surface joints shall then be roughly pointed flush with the surface of the slope protection II GRASSING OF SLOPES Grass shall be of species native to the country unless otherwise approved, harmless and inoffensive to people and animals and not of a kind recognised as a nuisance to agriculture It shall be free of disease and noxious weeds, deep rooted and sufficiently rapid growing and spreading to give complete cover over the planted area within two years of planting The term "grass" embraces sods, sprigs and seeds and, if the Engineer permits, may include plants of other types capable of giving effective protection Fertiliser shall be approved lime or mixtures of plant nutrients or both Sods and sprigs shall be planted with their root system substantially undamaged and packed around with moist earth in which they have grown Seeds shall be planted by a method that ensures reasonably uniform coverage and that the seeds will germinate and strike roots without being washed out Sprigs shall be planted in a regular pattern such that surface water flowing over the area will have no clear channels to flow through but will be diverted into winding course by the presence of the sprigs Sprigs shall be planted at a spacing of 300 mm or as required in the Contract Documents Sodding shall be done by planting sods to give continuous cover over the whole area Strip sodding shall be done by planting strips of sods not less than 80 mm wide, not more than 450 mm apart (centre to centre) or as required in the Contract Documents Strip sodding shall be planted with the strips lying along contours All sprigs and sods shall be planted with roots well buried in firm material Grass shall be planted at such a time and the work shall be done in such a way that at the time of the final construction inspection all areas to be grassed are substantially covered with healthy, well established, firmly rooted grass and the planted area is free from erosion channels In the case of strip sodding bare strips between the strips of sods will be permitted at the time of the construction inspection In the case of sprigging bare patches between sprigs will be permitted provided clear paths for erosion channels not exist PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 Occasional small bare patches will not be cause for rejection Any bare areas which, in the Engineer's opinion, may permit erosion shall be made good and replanted with sodding Surfaces to be planted, either by seeding, sprigging or sodding, shall be trimmed to the dimensions shown on the Drawings before any grassing is carried out Fertiliser shall be added at the time of planting if required in the Contract Documents or If it is necessary to ensure good ground cover within the required time Whenever a slope is completed, dressed and ready for grassing, the Contractor shall proceed with block sodding or strip sodding as designated on the Drawings or instructed by the Engineer The Contractor shall maintain the grass at his expense until the end of the Maintenance period Maintenance shall consist of preserving, protecting and replacing grass, and such other work as may be necessary to keep it in a satisfactory condition to prevent erosion and to present a dense and uniform appearance The Contractor shall be responsible for satisfactory growth and shall water, fertilise and mow the grass at such intervals as will ensure good ground cover of live grass all through the Maintenance Period PHUONG THANH TRANCONSIN ... CONTENTS I SLOPE PROTECTION II GRASSING OF SLOPES III GRABIONS PHUONG THANH TRANCONSIN GMS Ben Luc - Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 I SLOPE PROTECTION. .. Engineer The cut-off protection shall be constructed before laying the sacked concrete slope protection After cutoff masonry or sheeting has been placed and accepted the laying of slope protection shall... riprap or sacked concrete embankment slope protection shall be constructed at locations shown on the drawings or as directed by the Engineer This type of slope protection shall generally be used