JPS636685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of constructing a drainage ditch.

It is often necessary to remove water present in the soil, either temporarily, for example to facilitate the implementation of underground works, or permanently to protect existing works from groundwater or , in order to eliminate harmful effects arising from groundwater, especially from the standpoint of the stability of the soil itself.

Drainage trenches (soil trenches filled with permeable filter media that may or may not have longitudinal drainage pipes in the bottom) often adequately address the problems posed by water in the soil. However, the provision of drainage ditches can be overcome from both technical and economical points of view when drainage ditches require fairly deep penetration into the rock formations carrying the water. It may become difficult and may no longer be true.

It is known in fact to provide shallow drainage trenches, on the order of one meter of trenching, and it is now common practice to provide flexible filtration pipes as the trenching progresses. By reducing the size of the actual installation and speeding up the construction work, it became possible to close the trench again before the collapse of the wall at the start of excavation, which would hinder the installation of drainage pipes and construction work, occurred. Agricultural ditches use this method and are used to drain arable land for soil improvement.

Where deeper trenches are required, it is absolutely necessary to provide protection and support for the finished wall, reinforced with means of extracting water that has penetrated the main frame or the actual trench. . Alternatively, by using a device that draws out the flow of groundwater using pumping holes provided on both sides of the line where the trenching is being performed, the site where the trenching is being performed is, by definition, a geological formation that contains water.

It is well known that, at considerable depths, trenches are made subject to significant technical and economic constraints due to the use of the above-described main assembly, supports and pumping equipment.

This method uses the well-known technique of creating a concrete wall that is cast into the ground, and the trench is excavated while the trench is being protected with bentonite mud.

Nevertheless, the use of bentonite mud as a temporary agent for trench wall support is fundamentally inconsistent with the equipment and practical operation of trench drainage pipes.

Firstly, the supporting effect of bentonite mud is actually
The theory is that this mud penetrates into the soil near the excavation to a certain depth depending on the permeability of the soil composition, resulting in a seal or "cake" on the actual walls of the excavation. This is because it is possible. The combined effect of these two developments is only to oppose the circulation of water carried into the soil towards the drainage ditch.

Second, although a drainage pipe is installed to form a drainage trench, in reality it cannot be a drainage ditch as a result of the presence of bentonite mud. A method of equipping a drainage trench, in fact primarily by filling the trench with a permeable filtration material (e.g., using graded sized gravel); becomes completely clogged with mud.

It is therefore an object of the invention to provide a method which allows the construction of drainage trenches of considerable depth without the use of complex equipment.

The present invention provides a method for constructing a drainage moat according to the steps of (a) digging a moat underground; and (b) filling the moat with a filtration material.
(a) is carried out while filling a pseudo plastic slurry that can be broken down into trenches, and process (b)
The feature is that a filter material is placed in the moat filled with the slurry.

If necessary, a collection drainage pipe may be inserted into the base of the trench before step (b).

Pseudo-plastic used in the method according to the invention
Slurry or mud is a known product for use as a circulating fluid when performing excavations. The slurry or mud is made of a colloidal solution of a natural or biopolymer that is gel-like at rest. This slurry consists of dry polymer in water (approximately 5-10 parts polymer to 1000 parts water).
It is easily prepared by dissolving, has a pseudoplastic reaction (in other words, it can become a fluid when subjected to shear forces), and is degradable or reversible, in other words: It has the remarkable property of being able to return to a fluid state (similar to that of water) at the end of a certain period of time. This return to the fluid state occurs as a result of hydrolysis of the polymer, and as a result of enzymatic biodegradation, both of which can be controlled by the addition of inhibitors and by spontaneous chemical action. Natural or biopolymers suitable for the preparation of degradable pseudoplastic slurries are often heteropolysaccharides prepared from legume seeds and are commercially available from various manufacturers. ing. Examples include, but are not limited to, the following: ``RHODOPOL23'' sold by RHONE-POULENC, ``FORAGUM HM'' sold by CECA, and ``REVERT'' sold by JOHNSON. For more information on the actual preparation and decomposition of simulated plastic slurries, please refer to the instructions published with these products.

This slurry or mud has the consistency of a gel, allowing trenching or cuttings to be made without the risk of slipping or collapsing the trench walls.
Considered in one respect, it performs the same function as a trench pentonite slurry or mud that receives concrete to create walls that are formed into the ground. However, the applied pseudoplastic slurry has the advantage that it does not clog the filter material placed in the drainage ditch or the walls of the ditch. This is because it decomposes into a fluid similar to water. Its pseudoplastic behavior (its ability to become fluid upon application of shear forces) ensures that neither the insertion of filter media nor the insertion of collection drains is prevented.

The properties of the filter media used are not trivial. Currently, graded natural gravel is preferred,
It can be rolled or crushed, but artificial granules such as expanded clay balls, glass balls, etc. can also be used.

Instead of filling the trench with filter gravel, it is possible to fill the trench with prefabricated drainage panels made from granular materials such as clumped gravel, clumped expanded clay balls, etc. can. Alternatively, permeable bulk materials can be used, such as porous concrete or those with multiple open porosity.

Synthetic padding can also be used, for example by placing an assembled drainage panel in the center of the trench and placing loose filter material (such as gravel) in the space between this panel and the wall of the trench. ).

When using loose filter media, a perforated plate, such as a non-woven fiber cloth, is inserted between the loose filter media on the one hand;
On the other hand, it is a good idea to insert the filter between the trench wall and the base to prevent the surrounding soil from mixing with the filter material and clogging it, to a greater or lesser extent over time. The use of such perforated plates acting as separators allows the use of ungraded gravel.

The method according to the invention can be carried out either continuously or discontinuously.

Embodiments of the present invention will now be described with reference to the accompanying drawings.

Figure 1 shows the continuous construction of drainage trenches. In this figure, a degradable pseudoplastic mud or slurry 2 with the density of a gel in the absence of shear forces is shown.
The trench 1 is continuously excavated while being protected by. When the trench becomes longer than the corresponding length of the natural slope of the filter gravel filling the trench, filter gravel 3 is injected, generally pouring the gravel directly into the mud or slurry filling the trench. As shown, if it is chosen to provide a collection and drainage pipe 4 for the purpose of collecting wastewater in the trench, this pipe is laid at the bottom of the trench before the filtering gravel 3 is introduced. The pipe 4 may be made, for example, of a flexible or semi-flexible pipe of plastic material having holes all or part of its circumference. Excavation of the trench is carried out in the area indicated by 5 while gravel 3 is being poured into the already known trench section.

Since the length of slurry life is regulated as a function of different parameters that influence this (water PH, chemical composition, temperature, etc.), the decomposition of the slurry in any area of the trench is controlled by the trench. This only occurs after the drain pipe is installed and the filter media is completely filled. All necessary information regarding adjusting the longevity of the slurry can be found in the instructions for use of the natural or biopolymer used.

Once the slurry has broken down into a water-like residue (at the end of a period varying from a few hours to a few days), the trench divider is ready to perform its function.

FIG. 2 shows another method of carrying out the invention, according to which drainage channels are provided in successive sections. In this alternative embodiment, one section of the trench is excavated while protected by a degradable pseudoplastic slurry. part 1
Once a has been excavated, a drainage collection pipe 4 is inserted and, for example, when used at the bottom of section 1a, a temporary shutter or screen member 6 is inserted at the end of section 1a. This element 6 firstly retains the filter gravel 3 and secondly protects the pipe 4, which is housed within the reinforcement of the shutter element. After inserting the shutter member 6, pour the filter gravel 3 into the trench part 1.
It is possible to put it in a.

Once section 1a of the drainage ditch is completed, section 1b of the ditch is excavated using a degradable pseudoplastic slurry, the pipe 4 is unwound over the base of the ditch, and the shutter member 6 is placed at the end of section 1b. For this purpose, remove from the end of portion 1a and pour gravel 3 into portion 1b etc. until the drainage trench is completed.

It will be clear to the person skilled in the art that instead of making the drainage trenches in clearly successive sections, it is also possible to carry out the work on alternating sections.

Nevertheless, in this case the laying of collection and drainage pipes is not possible, at least not in a simple way.

In all cases, the geometrical characteristics of the drainage trenches (length, depth, actual location, etc.) shall be
It should be adapted to the type of terrain and rock formations under consideration.

The present invention is particularly necessary for stabilizing drainage on slopes and slopes where there is a limit to the equilibrium thereof, and
It is useful when carrying out large-scale soil excavation work required for the construction of railways, canals, etc., which is often encountered. Up to now, drainage stabilization has been achieved by creating a network of drill holes with much gentler slopes, and the drill holes generally begin at the edge of the relevant land. These “one-dimensional” drilling holes are generally one or several well-placed holes that are continuously drilled into the soil when water removal is attempted to carry out soil stabilization. It is much less effective than conventional drainage trenches, especially when such water circulates haphazardly within the formation.

The improvements proposed by the invention make it possible to provide drainage trenches under excellent economic conditions and with very good results, whatever the nature of the land encountered. It gives

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one method of carrying out the invention continuously, and FIG. 2 is a schematic cross-sectional view showing another method of carrying out the invention discontinuously. be. 1... Moat splitting, 2... Pseudo plastic slurry, 3... Filtration gravel, 4... Pipe.

Claims (1)

[Scope of Claims] 1. A method for constructing a drainage moat comprising: (a) digging a moat 1 underground; (b) filling the moat with a filter material 3;
Construction of a drainage ditch, characterized in that step (B) is carried out while filling the ditch with a decomposable pseudo plastic slurry 2, and step (B) is carried out by putting a filter material into the ditch filled with the slurry. Method. 2. The method according to claim 1, wherein the filter medium is gravel. 3. A method according to claim 1, characterized in that the filter medium is a prefabricated panel. 4. A method according to claim 1, characterized in that the filter medium is a combination of prefabricated panels and gravel. 5. The method according to claim 1, wherein the filter medium is a combination of gravel and a perforated plate inserted between the gravel.