The invention relates to the construction industry, namely, to geocell systems, and may be used for reinforcing water basin shorelines and beds, slopes, embankment cones, retaining walls in oil-and gas, transport, hydraulic engineering and other fields of construction, where geocells should have high and stable parameters of strength and endurance.

The prior art discloses GEOWEB geocell for slope stabilization, which is made of polymer strips interconnected in a staggered order with a preset pitch along their transverse ribs and fixed on a slope in their stretched state so as to form rhomboid cells (see, RU Patent No. 2152479, E02D17/20, 2000).

Also, one knows a geocell system which is formed by strips of a polymeric material arranged on a polymeric base so as to form cells for confinement of a bulk material, which walls are partially bent in the direction opposite to that of a slope grade (see: CH Patent No. 652155, E02D17/20, 1985).

One knows a geocell system which is made of a polymeric material with rhomboid cells formed by perforated polymeric strips when this geocell system is stretched, cell positions on a slope being fixed with anchors, and the cells themselves are filled with a bulk material (see: JP Patent No. 56016730, E02D17/20, 1981).

The known geocell designs for stabilization of soil structures cannot fully achieve the objective of fixing a material on a slope due to possible shift of such geocells down the slope under the influence of its filling material both during infilling a material into its cells and during the operation after infilling said material into cells, wherein said filling material being a peat-sand mixture, coarse gravel, or a combination of various bulk materials; in the result, a preset slope profile may be lost due to filling material accumulation at its base.

A preform for a stretched geocell system is known in the art that is made of a sheet material wherein slots of a segmental shape are made in rows, adjacent rows being offset relative to each other (see: RU Patent No. 2090702, 20.09.1997). Said slots may be provided with stretching said preform for forming a three-dimensional cellular structure A drawback of this preform is that plastic deformation of the sheet material occurs when it is stretched, which may result in non-equivalent strength of the geocell system. Moreover, since slots in the stretched state are used in the preform, thicknesses of walls (i.e., distances between the edges of neighboring slots) in different parts of a geocell system thus produced will not be equal. Stresses are concentrated in thinner parts of the walls, which reduces tensile strength of this geocell.

The closest analog of the claimed invention is a sheet preform, a weld-free web geocell system produced therefrom, as well as a method for producing said geocell system that are all described in the Prior Art section of RU Patent No. 2090702, 20.09.1997. This preform is made in the form of a polymeric sheet having slots that are offset relative to each other. A weld-free geocell system can be produced by stretching this preform. A drawback of this closest analog is also a low tensile strength of a geocell, since stresses are concentrated at the ends of said slots during stretching.

Geocells made from welded polymeric strips are known from US 2015/0225908 A1 and WO 2008/105879 A1. JP-S-55142609 discloses a preform according to the preamble of claim 1. None of said prior art documents disclose a preform and method of its use according to the present invention which is set out in the appended claims. The objective of the present invention is to eliminate drawbacks of the prior art solutions.

The technical effect consists in improving tensile strength of a geocell system and reducing labor-intensiveness of producing it.

The above technical effect is achieved in a preform intended for forming a weld-free geocell due to that it is made of a flexible sheet material provided with incisions having the central portion in the form of a straight line and two end portions in the form of an arc, said central portions of the incisions being arranged in rows, the incision lines in the neighboring rows being offset along the incision direction, the end portions of the incisions being provided with thickened areas, and the preform thickness in said thickened areas being up to 300% of the thickness of the main body of a sheet material.

Furthermore, the above technical effect is achieved in particular embodiments of the preform due to that:

• the end portions are capable to rotate the incisions by 90° relative to the central portion,
• the preform is made of a polymeric material,
• the thickened areas at the end portions of the incisions are shaped as a circle or an oval,
• the preform has additional thickened areas made in the area of the incision central portions,
• the preform thickness in said additional thickened areas is up to 300% of the thickness of the main body of a sheet material,
• the preform is made in the form of a strip,
• a sheet material is reinforced with a thread or mesh,
• an aramid or carbon thread is used for reinforcement,
• the incision central portions have the same length L,
• neighboring central portions of incisions in a row (R₁, R₂, ...R_N) are arranged at a distance S between their ends, and the ratio S/L = K1, where K1 is from 0.1 to 0.5, preferably from 0.3 to 0.35,
• central portions of incisions in neighboring rows (R₁, R₂, ...R_N) are arranged at a distance D from each other, and the ratio D/L = K2, where K2 is from 0.1 to 0.7,
• the incision end portions project by a distance L1 relative to the central portion, L1 being from 1/10L to 1/15L,
• the preform is provided with additional holes for tendons used for attaching a geocell system in the stretched state to a slope,
• the additional holes for tendons are arranged between the neighboring incisions in a row (R₁, R₂, ...R_N),
• thickened areas are made around the additional holes, the preform thickness in these areas being up to 300% of the thickness of the main body of a sheet material,
• the preform is provided with drainage holes,
• the sheet material is made textured,
• the incisions are made by a laser cutting or notching.

The above technical effect can be achieved by a weld-free geocell system that comprises at least one said preform stretched in the direction perpendicular to the incision lines so as to form a three-dimensional cellular system.

Furthermore, the above technical effect can be achieved in particular embodiments of the geocell system due to that:

• at least one tendon is drawn through the preform for the purpose of fixing the geocell system on a slope,
• the geocell system can be composed of several said preforms forming the system sections that are interconnected by said tendon,
• the geocell system can be composed of several said preforms forming the system sections that are interconnected by ultrasonic welding or metal clips,
• the geocell system may be made with the possibility of filling its cells with fillers, such as sand and/or coarse gravel, and/or peat-sand mixture, and/or concrete,
• the geocell system is also provided with a support made of a geotextile material.

The invention is explained by the accompanying drawings, wherein:

• Fig. 1 shows a preform suitable for producing a weld-free geocell system;
• Fig. 2 shows a general view of an incision made in a preform,
• Figs. 3-5 show variants of incision areas in a preform,
• Fig. 6 shows a weld-free geocell system (the preform is stretched).

The claimed preform for producing a weld-free geocell system (Fig. 1) is made of a sheet of a flexible material (1), in particular a polymeric material, a fabric based on chemical fibers (carbon fibers, glass fibers) or another type of material. The sheet (1) is provided with incisions 2 (Fig. 1) for forming cells. These incisions (2) consist of a central portion (3) in the form of a straight line and two end portions (4) in the form of an arcuate lines that ensure rounding (turn) of the ends of the incisions (2) (Figs. 2-5).

This configuration enables the most optimal redistribution of loads in a geocell system in the area of incision end portions, and, in the result, improves the system tensile strength.

In one embodiment of the system, the end portions (4) are made so as to enable turn of the incisions by 90°, i.e., the end portion has at its end a section that is perpendicular to the central portion (3). However, other variants are also possible for orienting the ends of an incision (2). The central portions (3) of the incisions (2) are arranged in rows (R₁, R₂, ...R_N), the incision lines in the neighboring rows being offset in the incision direction (Fig. 1). Preferably, the incision end portions are oriented toward one side.

The end portions (4) of the incisions (2) are provided with thickened areas (5) (Fig. 3). These thickened areas (5) may have the circular or oval shape in the plane view (in the longitudinal section).

Other variants of shapes are also possible.

In one preferable embodiment, the preform may be provided with additional thickened areas (6) located in the area of the central portion (3) of the incision (2).

These thickened areas (6) may be shaped as a rim going along the direction of the central portion (3) of the incision (Fig. 4) or as a solid rectangle in the plane view (Fig. 5). The sheet thickness in the thickened areas may be up to 300% of the thickness of the sheet material in the other areas.

These thickened areas (5, 6) ensure additional strengthening in the area of the incision (2), thus improving tensile strength of a geocell system.

The central portions (3) of the incisions (except for those at the sheet edges) have the same length L and are disposed at the same distance S between the ends of the adjacent incisions in every row (R₁, R₂, ...R_N) (in the longitudinal direction) and at the same distance D between the incisions of adjacent rows (R₁, R₂, ...R_N) (in the transverse direction). The relationship S/L = K1, the K1 value ranging from 0.1 to 0.5, most preferably from 0.3 to 0.35; and the relationship D/L = K2, the K2 value ranging from 0.1 to 0.7.

The coefficients K1 and K2 are selected from the above ranges, depending on particular conditions of the geocell system application. For example, if the claimed geocell system is used for reinforcing a slope with the gradient angle of 45°, the coefficient K2 should be equal to 0.7; for slopes with the gradient angle of 30° the coefficient K2 should be equal to 0.2. Preferably, the end portions (4) of the incisions (2) project by the distance equal to the length L1 relative to the central portion (3) (Fig. 1), L1 ranging from 1/10L to 1/15L.

In preferable embodiments of the invention, the sheet material 1 is provided with additional holes (7) for tendons (Fig. 1, 6) that are intended for fixing a geocell system in the stretched state on, for example, a slope. The holes (7) for tendons are arranged on the rows (R₁, R₂, ...R_N) between the incisions (2). Thickened areas (8) shaped as circular rims may be made around these holes.

Furthermore, the sheet 1 may be also provided with drainage holes (8) (Fig. 6) that are intended for draining water from the soil reinforced with the geocell system.

In one particular embodiment, the sheet (1) of a flexible material may be additionally reinforced in the areas (9) with high-strength threads, e.g., made of aramid (e.g., Kevlar, SVM) or carbon (Carbon) or other fibers that increase the preform strength in the transverse and longitudinal directions, which makes the geocell system uniformly strengthened due to the absence of unreinforced welds therein.

Furthermore, the surface of the preform sheet material (1) may be made textured in order to improve the adhesion of the geocell system to soil.

The sheet (1) may be made of a color polymeric material, which enables to use the stretched geocell system for advertising or information purposes.

Preferably, the incisions (2) in the sheet material (1) can be made by a laser cutting technique, which can further strengthen the system due to melting of the cut edge and, thereby, eliminate micro damages on the edge. Also, the incisions (2) may be made by notching by means of a punch.

A preform sheet intended for transportation may be reeled together with a geotextile material serving as the support (11) for the geocell system into a two-layer roll (Fig. 6), the geotextile material having small folds enabling it to stretch, when a strip is stretched, in such a way that it would be completely smoothed after the geocell system is layered on a slope.

The geocell system may be produced from one or more said preforms by stretching (preferably, without plastic deformation) in the direction perpendicular to the lines of the incisions (2) for forming a three-dimensional cellular structure wherein the cells of the geocell system, as formed during stretching of the preform, are connected by means of necks (10) (Fig. 6). The ends of the system should be fixed on soil with the use of anchors. If several preforms (i.e. sections of the geocell system) are used, the last holes 4 in the adjacent sections are aligned with each other, and tendons are drawn therethrough, thus connecting adjacent sections and, at the same time, fixing the geocell system. Sections may be also interconnected by ultrasonic welding, metal clips or other connectors.

Depending on the application of the system, its cells may be infilled with various fillers, such as sand, coarse gravel, peat-sand mixture, concrete, etc.

The use of the proposed preform structure and a geocell system produced therefrom enables to achieve the following advantages:

• a reduced degree of washing out of the system filler, what is especially important when reinforcing slopes,
• expanded possibilities for using the geocell system for new applications requiring higher performance, e.g., on slopes and in cones of bridges on rail and motor roads, in protection facilities of pipelines and soil embankments, for bank stabilization, etc.,
• improved strength of the system in comparison with three-dimensional geocell systems produced by welding of polymeric strips,
• significantly higher draining capability of the system,
• lower mounting costs of the system,
• if cells are to be infilled with concrete, the geocell system may be used for ascending a slope by using steps thus formed,
• furthermore, it is also possible to use the geocell system as an information or advertising space.