Brief Introduction of Construction of EPDM Waterproof Membrane in Anti-seepage Project

1.CONSTRUCTION CONDITIONS

1 ,The main indexes of EPDM waterproofing membrane shall be inspected before construction.

2、Before laying the membrane, the site shall be leveled to be smooth, and all sharp and hard objects that may damage the composite EPDM waterproofing membrane, such as stones, iron wires and tree roots, shall be removed.

3、When laying, should strive for smooth,The tightness is moderate, leaving enough allowance, no distortion, wrinkle and overlap, so as to facilitate splicing and adapt to temperature changes, and should be close to the surface of the foundation soil, without leaving gaps.

4、When the EPDM waterproofing membrane is laid to the corner of the surrounding buildings, attention should be paid to proper cutting, and the proper connection between the EPDM waterproofing membrane and the surrounding buildings should be ensured to form a complete anti-seepage system.

6、The parts connected with EPDM waterproofing membrane on the structure shall be cleaned, and the local unevenness shall be leveled with cement mortar, so as to connect with EPDM waterproofing membrane tightly.

★  Construction of canal seepage control works

1,Basic structure and requirements of construction

Single-layer impermeable structure, double-layer impermeable structure or composite impermeable structure can be selected according to the engineering conditions. The impermeable structure includes an upper cushion layer of impermeable material, a lower cushion layer, a protective layer on the upper cushion layer, a support layer and a drainage layer on the lower cushion layer (see Figure 1).

1.1, support layer; according to the project category, natural foundation conditions and the characteristics of the EPDM waterproofing membrane used to choose. Generally used 50~150mm thick sand. It can also be covered with 1 layer of geosynthetics or 1 layer of geosynthetics on the sandy soil.

1.2. Lower cushion; fine soil layer, fine sand layer, concrete layer, geotextile, geotextile, etc. with a thickness of more than 100mm shall be adopted. When the soil quality of the base layer is uniform and smooth fine-grained soil or the composite EPDM waterproofing membrane is adopted, no cushion layer can be set.

1.3. Drainage layer; When the groundwater level is high and there is internal water pressure, a drainage layer or drainage and exhaust facilities shall be laid between the support layer and the EPDM waterproofing membrane. Such as water stop valve, drainage pipe, vertical and horizontal drainage ditch, etc.

1.4. Upper cushion; foam plastic sheet, geotextile, gravel, sand-free concrete, asphalt concrete, geonet, etc. When the protective layer is compacted fine-grained soil with sufficient thickness or the composite EPDM waterproofing membrane is adopted, the cushion layer may not be provided.

1.5, protective layer. According to the type of anti-seepage EPDM waterproofing coiled material and upper cushion layer, channel slope selection, and to meet the requirements of frost resistance, compacted plain soil, sand gravel, prefabricated or cast-in-place concrete slab, mortar masonry or dry masonry can be used.

2、Laying method

According to the scope of film laying, it is divided into three modes: full laying type, half laying type and bottom laying type. Among them, the half-paved and bottom-paved types are mainly applicable to wide and shallow channels or reconstructed channels with trees on the canal slope.

2.1, fully paved; channel slope and channel bottom are fully paved. The laying method can be selected according to the anti-sliding stability of the channel slope, and the specific methods are: trapezoid, step, zigzag, pentagon, etc. (see Figure 2).

2.2, semi-paved type; The bottom of the canal is fully paved, and the height of the canal slope film is 1/2~1/3 of the normal water level of the canal (see fig. 3).

2.3, bottom shop type. Only lay the bottom of the canal (see Figure 4).   

3、Construction Procedure of Channel Works

Construction operation procedures: cleaning the foundation trench → laying of EPDM waterproofing membrane → joint construction, inspection → connection and anchoring with the surrounding → acceptance → protective layer construction.

3.1. Clean the foundation trench

Peel according to the design, remove the silt, garbage, trees, grass roots, stones and all other sharp edges that may damage the EPDM waterproofing membrane within the scope of laying EPDM waterproofing membrane. The land shall be leveled and compacted, pits and cracks shall be repaired, and the anchoring trench shall be well dug. When there are yin and yang angles on the base, it shall be rounded with a radius of not less than 0.5m; Drainage shall be carried out in areas with accumulated water and high underground water level.

3.2, EPDM waterproofing membrane laying

According to the different types of EPDM waterproofing membrane and design requirements, the appropriate seam splicing method is selected.

1) When selecting welded joints, the construction process is as follows: laying, tailoring → alignment, laying together → film pressing and shaping → wiping dust → welding wiping inspection → welding → inspection and repair → reinspection → acceptance.

2) When the composite EPDM waterproofing membrane is selected, the construction process is as follows: laying membrane welding membrane → sewing bottom cloth → sewing surface cloth (2 cloth and 1 membrane). Stitching requires moderate tightness and natural smoothness to ensure that the membrane and cloth are stressed together.

3) When laying EPDM waterproofing membrane in the channel, the laying direction can be determined according to the actual situation of the project, with the principle of minimum joints, convenient construction and reasonable tailoring. The joints should avoid corners and be located in the plane.

4) When the foundation trench is soil, water should be sprayed first to make EPDM waterproofing membrane closely combined with the foundation trench of the canal bed. When the foundation trench is of concrete structure, filament hot-rolled composite EPDM waterproofing membrane should be selected and the foundation trench should be bonded with cement adhesive containing 2.0%SBC120 adhesive (cement weight).

5) When laying EPDM waterproofing membrane, it should be parallel or perpendicular to the slope line from downstream to upstream in turn, do not pull too tightly, and leave 1.5% slack in both vertical and horizontal directions.

6) The laying height of EPDM waterproofing membrane on the channel slope shall reach above the highest water level and have a certain superelevation. The superelevation value shall be determined according to the water level or wave climbing, which shall not be less than 0.5m and shall be fixed.

7) When EPDM waterproofing membrane is welded, the surface of the base should be dry, the moisture content should be below 15%, and the membrane surface should be wiped clean with dry gauze.

3.3, coupling and anchoring

1) EPDM waterproofing membrane is connected with the soil base. EPDM waterproofing membrane is directly buried in the anchoring ditch, filled with soil and tamped. Water seepage or pull out shall not be allowed at the anchoring place (see Figure 5,a and B).

2) The connection between EPDM waterproofing membrane and building concrete can be riveted with angle steel or metal lath, or fixed on the concrete layer with bolts (see Figure 5,c).

Construction of 3.4 and protective layer

1) When the protective layer is a concrete structure, expansion joints shall be reserved according to the design.

2) When the soil protective layer is filled by compaction method, it is forbidden to use the horn roller.

3) When the protective layer of sandy loam, light loam and medium loam is filled by the immersion method, 10-15% of the subsidence amount shall be reserved for the filling section size. After repeated immersion and subsidence are stable, slowly drain water, fill cracks, and pat them to make the section as required by the design.

4) Combined protective layer with different impact resistance and different materials can be used for the bottom, slope or different sections of the canal..

4、Precautions

１）The excavated section and elevation of the channel shall meet the design requirements. Excessive excavation of the canal bed section shall be avoided. The filling section shall be watered and compacted in layers, and the collapsible canal section shall be pre-subsided or tamped by immersion to avoid large deformation.

2) For projects with anti-freezing requirements, anti-freezing measures shall be taken for the anti-seepage structure. Rigid foam plastic insulation layer can be laid under the anti-seepage layer, or non-frost heaving soil can be replaced. In general, the insulation layer can be laid in full section.

3) The construction shall be carried out in accordance with the current relevant national standards. Comply with Technical Code for Application of Geosynthetics (GB50290-98) and Technical Code for Channel Seepage Control Engineering (SL18-91).

★ Anti-seepage construction scheme of EPDM waterproofing membrane

(I),CONSTRUCTION CONDITIONS

1、 With AC 220V power supply;

2、 The temperature should be between 5 ℃-40 ℃, no more than five wind, no rain or snow weather;

3、 The soil surface foundation shall be compacted without hard objects such as roots and weeds;

4、 The foundation surface shall be free from accumulated water and hard sundries such as bricks and stones, and shall be kept flat and clean.

(II),Laying

The laying method is shown in Figure 6.

1、 Lay in sequence, with overlapping width of 8cm-16cm,(depending on the width that the machine can accommodate) and weld with laying, and avoid four-layer joints at the same point on the same line for length joints. For the joint method, see Splicing Method Figure 7.

2、 When laying EPDM waterproofing membrane, it is allowed to have no serious unevenness, but there shall be no dead fold. When there is dead fold that cannot be corrected, it shall be crossed off, disconnected and welded again. When there are sundries in the cover of EPDM waterproofing membrane that cannot be taken out, it shall also be scratched out and then welded.

3、 For the single-line weld of EPDM waterproofing membrane with a thickness of more than 1.2mm, that is, the full thickness of the upper membrane edge shall be chamfered by 45 degrees with a grinder before extrusion welding, and then welded.

4、 The vault, wall surface, and EPDM waterproofing membrane can be mechanically anchored with anchor pads and then welded, and then the joints are welded. The anchor points can be preset in a plum blossom shape according to the environment.

(III),Engineering quality inspection

Seam inspection methods include visual inspection method, inflation method, vacuum method and sampling test method.

1、 All welds shall be visually continuous. The hot wedge welder and the root of the exposed edge of the weld can be crossed with a test rod, and there shall be no welding leakage. There shall be no air leakage at the air filled 0.2MPa weld in the air passage, and there shall be no open welding. The pressure holding time of 0.2MPa shall not be less than 10 seconds.

2、 Extrusion welds and doubtful points of leakage can be inspected by vacuum leak detector. There shall be no air leakage. The pressure holding time under the vacuum degree of 0.02-0.03MPa shall not be less than 10 seconds.

3、 Prefabricated yin and yang angle can be tested by water, and there should be no leakage in 5 minutes.

4、 Anchorage point, shear tension ≥ 2kg.

5、 All welds can be tested for failure, that is, the universal material test, the shear force should be greater than or equal to 70% of the fracture tensile force of the base metal. Do the peeling test, as long as the peeling surface is not 100% peeling, it is qualified.

(IV),Matters needing attention in construction

1) Operators must be trained before taking up their posts;

2) All tools on the impermeable layer must be handled with light, and hot tools are strictly prohibited from contacting with EPDM waterproofing membrane.

3), it is strictly prohibited to wear shoes personnel to enter the EPDM waterproofing membrane construction site, no smoking;

4) Pay attention to site protection during construction to prevent wind blowing;

5), strictly check the welding quality with crochet needle point by point, to see if there is no leakage of welding, welding phenomenon;

6), covering the protective layer while construction side inspection, if there is damage, must be timely repair.

Construction machinery table

● Labor forcePersonnel Requirement Schedule

Note: The above construction number is for reference only, and the specific number can be slightly adjusted according to the construction area.

5. quality assurance measures

1), should use matching paving material, adopt EPDM waterproofing membrane waterproofing system;

2) Operators must be trained before taking up their posts;

3) The welder shall ensure uniform welding with molten slurry;

4), strictly with a flat screwdriver point by point to check the welding quality, to see if there is no leakage of welding, welding phenomenon.

5), the site should pay attention to the protection of finished products, to ensure construction safety