DE69838697T2 - Geosynthetic reinforcing layer for settling soil - Google Patents

Abstract

The material comprises at least one layer of parallel and alternating reinforcing strands from two groups: the first group is made with fibres having a high tension module and a breaking elongation of about 5%, while the second is made with fibres having a lower tension module and a breaking elongation of at least 12%. Preferably the fibres in the first group of strands are of polyvinyl acetate, while those in the second group are of polyester or polypropylene. The material can be made from a knitted fabric associated with a non-woven fabric.

Description

The The invention relates to a geosynthetic for strengthening earthworks.

geosynthetics and especially geotextiles are becoming more common as rebars during construction of earthworks, for Roadways or railroad tracks used.

Some geotechnical difficulties can be relatively well identified and processed appropriately and finally or treated. Other geotechnical difficulties are more difficult to narrow down and sometimes get the engineer to risk management to operate.

This is especially the case when the terrain underground cavities natural Origin (karst phenomenon) or of anthropogenic origin (sub-excavations, marl pits, etc.) which are not registered and difficult to narrow down. Of the Building an earthwork on this type of terrain is sometimes unavoidable and thus involves a geotechnical risk associated with the random Formation of terrain bagging or break-in (Breaking fields) in the infrastructure area is connected and with for the structure required service level is incompatible.

The technical solution goes over a reinforcement geotextile of the type "parachute", that preventive is used. The properties of this geotextile are from his Surfaces- or depth position, of the extent of the break fields to be processed as well as the maximum allowable permanent and dynamic displacement or deviation on the surface depending on the time of surgery for depending on the repair of the building. It must be the lifetime of the reinforcement after occurrence of the break field dependent on traffic on the roadway above the building are taken into account.

at The definition of the tensile modulus of the geotextile to be selected is different Parameter.

The The aim of the invention is to propose a geosynthetic which a normal operation during the use of the building allows and in the case of a Collapse or sagging of the terrain a security solution from Type parachute supplies.

The The invention therefore relates to a geosynthetic comprising at least one Layer composed of parallel reinforcing threads.

This Geosynthetic is characterized in that the reinforcing threads in a first group threads which are formed with a fiber, which has a high tensile modulus and has a breaking elongation value close to 5% and a second group of threads, which are formed with a fiber, which has a lower tensile modulus as the fiber of the first thread group and a breaking elongation value of at least equal to 12%, are divided.

advantageously, is the fiber of the threads the first group of PVA (polyvinyl acetate), which has an elongation at break in the order of magnitude of 5%. It should be noted that other fibers, such as glass or Aramid can be used which have a maximum elongation at break of 2 or 2.5%, which for break field areas is too low.

The Fibers of the threads the second group are preferably made of polyester or polypropylene.

Lies in the ground no serious disturbance before, all threads are the two groups at the admission of the loads up to the deformation value actively involved by 5%.

From this value, which corresponds to the beginning of a serious disorder, the threads start the first group to break, and the absorption of forces takes place also solely about the Threads of second group, reflecting a greater deformation of the geosynthetic The parachute type is expressed, however, the threads of the second group, the a fracture deformation value of over 12% support the structure despite the severe disturbance in the ground.

In In practice, the geosynthetic according to the invention can advantageously be assigned to a second geosynthetic during construction of the structure, equipped with threads is at predetermined strain values, for example of 4 and 8% can break and which are connected to alarm devices, this second Geosynthetic is placed on the ground and of the geosynthetic according to the invention separated by a layer of earth that is under its own weight a deformation of the second geosynthetic of, for example, 5% which results in the insertion of one of the alarm devices.

Further Advantages and features of the invention will become apparent upon reading the following, given as an example description with reference to the accompanying drawings emerge, in these show:

1 the characteristic of the elongation of the geosynthetic according to the invention as a function of the lateral forces exerted on it per unit length;

2 an example of the structure of the geosynthetic according to the invention;

3 a cross section of the geosynthetic of the 2 along the line III-III;

4 a use example of the geosynthetic according to the invention in a building above a region that can collapse;

5 a cross section of the building of 4 above a collapsed area.

In 1 the characteristic (C) of the elongation of the geosynthetic according to the invention is shown as a function of the forces exerted on this geosynthetic in the longitudinal or transverse direction of the reinforcing threads of this geosynthetic. This curve (C) is instructive in terms of tensile strength. This can be advantageously adjusted depending on the needs of the terrain.

If the elongation is less than 5%, the curve (C) has a steep slope on. Up to an elongation of 5%, the forces are due to the high tensile modulus and a breaking elongation value of 5% reinforcing threads, which preferably made of PVA (polyvinyl acetate), and by the others Reinforcing threads that a significantly lower tensile modulus and a tensile elongation value from above 12% and preferably equal to 18%, recorded, these other threads For example, made of polyester or polypropylene.

If the elongation exceeds 5%, break the PVA threads, and the load is then absorbed by the polyester filaments.

If the elongation reaches 5.5%, all PVA threads are broken, and the forces become taken solely by the polyester threads.

Of the Section OA of the curve C corresponds to a normal mode of operation of the geosynthetic in a building. Section AB corresponds an alarm situation, and section BD corresponds to the use of the geosynthetic in the parachute mode, for example in the case of Collapse of the terrain under a equipped with the geosynthetic according to the invention Building.

The 2 and 3 show a geosynthetic made in jersey fabric technology 10 , including fleece, which in its transverse direction a plurality of parallel threads or ropes 11 . 12 which is in a first group of threads 11 made of PVA fibers and into a second group of filaments 12 , which are made of polyester or polypropylene fibers, are divided.

The strings 11 and 12 be in the course of making the geosynthetic 10 integrated with a perfectly straight-lined arrangement, which produces no ripple or shear as in other textile surfaces.

In the 2 and 3 are the threads 11 made of PVA and the threads 12 made of polyester or polypropylene arranged alternately. It is obvious that the density of the two types of yarn can be different and depending on the use of the geosynthetic 10 can be calculated.

The 4 and 5 show a beneficial use of the geosynthetic 10 in a building 20 that on a ground 21 is arranged, the internal cavities 22 that has through vaults 24 from the surface 23 of the soil 21 are separated. Above the surface 23 becomes a first geosynthetic 25 arranged, comprising threads, which are suitable to break then, when the expansion coefficient of the first Geosynthetikums 25 4%, for example, to signal a first alert level, and threads capable of breaking when the expansion coefficient of the first geosynthetic is, for example, 8% to provide a second alert level.

Between the geosynthetic according to the invention 10 and the first geosynthetic described above 25 a bottom layer H is arranged, which is calculated such that the first geosynthetic 25 Under the weight of this layer H undergoes a deformation greater than 4%.

If it is under the first geosynthetic 25 If the collapse occurs, the weight of layer H will result in breakage of the low elongation at break yarns and provide a first level of alarm.

Under this condition, the geosynthetic according to the invention carries 10 alone the weight of the structure 20 , Beyond a certain deformation of the geosynthetic 10 (5 to 6%), this will add additional forces to the first geosynthetic 25 which leads to breakage of the filaments with high elongation at break of the first geosynthetic 25 and to provide the second alert level. This second alert will be at a deformation of the geosynthetic 10 on the order of 6 or 7%, which is well below the breaking strain of the polyester threads of the geosynthetic 10 lies.

TRANSLATION OF THE TEXT IN THE DRAWINGS

Fig. 1 Bi module PVA-PP Bi-module PVA-PP Force KN / m Force KN / m Allongement% Strain %

Claims (4)

A geosynthetic material of the type comprising at least one layer of parallel reinforcing filaments, characterized in that said reinforcing filaments form a first group of filaments formed with a fiber having a high tensile modulus and elongation at break value close to 5%, and a second group of Filaments formed with a fiber having a lower tensile modulus than the fiber of the first filament group and a tensile elongation value of at least equal to 12% are divided. Geosynthetic according to claim 1, characterized in that that the Fiber of the threads the first group consists of polyvinyl acetate. Geosynthetic according to any one of claims 1 or 2, characterized in that the fiber the threads the second group consists of polyester or polypropylene. Geosynthetic according to any one of claims 1 to 3, characterized in that it is made of jersey fabric including fleece.