Selection of geotechnical materials and engineering practice

Preparation of geotechnical materials: the performance index of the purchased composite geotextile conforms to the national technical standard of composite geotextile: GB / T, which has specific parameter requirements for various specifications of composite geotextile.

 Construction conditions

 Base preparation:

1) Check and confirm that the foundation support layer has the conditions for laying composite geotextile. The base surface shall be dry (moisture content shall be controlled below 15%) and compacted (dense and uniform, with compaction coefficient ≥ 0.95). The surface shall be flat, free of cracks, mud, depression and uniform gradient. The straightness of the geotextile shall be changed smoothly, and the internal and external corners shall be smooth.

2) Clean the laying surface of geotextile without sharp objects, stones, wires, sticks, etc. the turf and roots within the impervious range shall be removed, and the weeds shall be sprayed with herbicide.

 Preparation for Geotextile laying:

1) Cutting analysis and reasonable cutting.

2) Check the appearance of composite geotextile, record and repair the damage, holes and other defects;

3) Do the test section, determine the welding temperature, speed and other construction process parameters.

4) Before laying the composite geotextile, both sides of the surface shall be static pressed by the roller.

The main labor force required for each construction technician: 1 mechanic (responsible for lifting the composite geotextile), 1 setting out worker, 1 electrician, 5-6 auxiliary general workers (can be adjusted with the progress of the project).

3、Construction process

Base treatment - geosynthetics laying - overlapping treatment - Inspection and acceptance - backfilling

4、Construction method

Base treatment

1) The base course for laying composite geotextile shall be flat and the local height difference shall not be greater than 50 mm. Remove tree roots, grass roots and hard objects to avoid damage to the composite geotextile.

 Laying of composite geotextile materials

1) First, check whether the material is damaged.

2) The composite geotextile shall be laid according to its main stress direction, and shall not be pulled too tightly, and a certain amount of expansion shall be reserved to adapt to the deformation of the matrix..

3) When laying, it shall be tightened manually, without wrinkles, and close to the lower bearing layer. It shall be pressed and consolidated in time as the pavement is laid to avoid being lifted by the wind. Construction shall not be carried out in case of ponding or rain, and the bentonite cushion laid on the same day must be covered with backfill.

4) When the composite geotextile is laid, there must be surplus at both ends. The surplus shall not be less than 1000mm at each end, and shall be fixed according to the design requirements.

5) Both sides of the composite geotextile are reserved with a certain width of PE film and PET fabric non bonding layer (i.e. edge rejection). When laying, the direction of each unit of composite geotextile shall be adjusted to facilitate the welding of the two units of composite geotextile.

6) For the laid composite geotextile, the edge joints shall be free of oil, water, dust, etc.

7) Before welding, adjust the PE single film on both sides of the joint to make it overlap a certain width. The overlap width is generally 6-8cm and flat without white crease.

The double rail welding machine is used for the welding of composite geotextile. The surface of PE film connected is heated by the hot welding method to melt, and then it is melted into a whole by the pressure.

1) Overlap width of weld bead: 80 ~ 100mm; natural fold of plane and vertical surface: 5% ~ 8%; reserved expansion: 3% ~ 5%; leftover material: 2% ~ 5%.

2) The working temperature of hot-melt welding is 280-300 ℃; the traveling speed is 2-3m / min; the welding mode is double rail welding.

3) The damaged parts shall be repaired by cutting materials of the same specification, hot-melt bonding or sealing with special geomembrane glue.

4) For the connection of non-woven fabric at the weld bead, if the composite geotextile on both sides is below 150g / ㎡, it can be welded with hot air welding gun, and above 150g / ㎡, it can be sewed with portable sewing machine.

5) The sealing and sealing of the underwater pipe mouth shall be sealed with GB rubber waterstop, wrapped with metal and treated with anti-corrosion.