Geosynthetics is a new kind of geotechnical engineering material. This paper briefly introduces the construction points of several synthetic materials widely used in engineering, such as geotextiles, anti-seepage films, geotechnical moulding bags and plastic drainage boards, for exchange and reference.

I. Construction of Geotextiles

Geotextiles are permeable geosynthetics. When geotextiles are used as filters, paving fabrics should have uniform wrinkles to maintain a certain degree of tightness, so as to prevent the fabric from deforming with elastic limit when paving stones. In most cases, the fabric filter can be directly laid on the repaired soil, but when the content of silt or clay in the underlying soil exceeds 50%, a sand layer should be laid under the fabric to reduce the risk of clogging. For example, the clay content of the earth dam of Taipinghu Reservoir is relatively high. In order to prevent the clogging of fabric by soil particles, a 10 cm thick coarse sand layer is laid under the fabric, and the effect is very good. Generally, there are:

(1) lapping, which means that two adjacent fabrics overlap partially. Generally, the lapping width is at least 50 cm in water and at least 100 cm in underwater.

(2) Sewing, that is, two pieces of fabric are sewn with nylon or polyester thread. The method includes opposite seam and folding seam.

(3) Nailing, the connection method is to use U-shaped nails to connect two pieces of fabric. The folding type is preferable for joints and nails should be prevented from rusting.

(4) Adhesion, using heating or binder or double-sided adhesive, the bonding width is 10 cm. This method saves a lot of work, but the process is complicated.

II. Construction of Anti-seepage Film

Geomembrane is a geosynthetical material with low permeability. In order to make the film play its due anti-seepage role, besides requiring the film itself to be impermeable, attention should also be paid to the construction quality of laying anti-seepage film.

(1) The contact surface between the anti-seepage film and the supporting material should be smooth so as to prevent the film from losing its anti-seepage effect by stabbing the slope. Otherwise, fine-grained cushion should be installed to protect the film from damage.

(2) The connection of the anti-seepage film itself. There are three ways to connect impervious films, i. e. bonding, welding and vulcanization, depending on the raw materials of the films. The impermeability of all joints should be checked to prevent leakage due to poor connection.

(3) The connection between the impervious film and the surrounding boundary. The anti-seepage film must be closely combined with the surrounding boundary. During construction, anchor grooves can be excavated to connect the foundation and bank slopes.

III. Construction of geotechnical moulding bags

Geomembrane bag is a kind of double-layer fabric woven with synthetic fibers. It can be filled with concrete or mortar with certain fluidity. Geotechnical bag is a form of bank protection and slope protection. Geotechnical bag construction can usually be divided into preparation before laying, laying and filling material filling and maintenance and other aspects.

(1) Preparing before laying. Before laying, we should know and master the topography, standard design section, hydraulic elements and natural conditions of geotechnical bag laying section. According to the design section, the slope is repaired and the roots, rocks and other debris are removed. The necessary equipment and equipment should be prepared before construction.

(2) Preparation and laying of geotechnical moulding bags. According to the topography and cross-section shape of the paving section, considering the convenience of manual removal, a die bag is usually made of six pieces of seam. When sewing and laying geotechnical moulding bags, the longitudinal and transverse shrinkage of moulding bags filled with mortar or concrete must be considered.

(3) Filling of filling material. Whether it is single-bank revetment or simultaneous revetment on both sides, the filling procedure is: bottom slope bank washing. In order to ensure the compactness of the filling material, the positioning in the filling process of geotechnical moulding bags and the longitudinal and transverse free shrinkage of moulding bags are utilized.

IV. Construction of Plastic Drainage Plates

The construction procedure of plastic drainage board is: laying geotextile on foundation as isolation layer, then laying medium and coarse sand with thickness of at least 30 cm on geotextile to play the role of horizontal drainage, then clamping the plastic drainage board into the steel plate of the splitter, inserting into the soft soil foundation, pulling out the steel splints on both sides, leaving the plastic drainage board in the foundation, then laying geotextile isolation layer, filling. Build a dyke.