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WO1998002616A1 - Procede de consolidation d'un sol aqueux - Google Patents

Procede de consolidation d'un sol aqueux Download PDF

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Publication number
WO1998002616A1
WO1998002616A1 PCT/NL1997/000405 NL9700405W WO9802616A1 WO 1998002616 A1 WO1998002616 A1 WO 1998002616A1 NL 9700405 W NL9700405 W NL 9700405W WO 9802616 A1 WO9802616 A1 WO 9802616A1
Authority
WO
WIPO (PCT)
Prior art keywords
pump
ground
drainage
groundwater
drainage element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/NL1997/000405
Other languages
English (en)
Inventor
Abraham François VAN WEELE
Leendert-Jan Van Der Pligt
Antonie De Moree
Philippe Groen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gebr Van Kessel Bv
IFCO FUNDERINGSEXPERTISE BV
KONINKLIJKE WEGENBOUW STEVIN BV
VERMEER GROND EN WEGEN BV
Original Assignee
Gebr Van Kessel Bv
IFCO FUNDERINGSEXPERTISE BV
KONINKLIJKE WEGENBOUW STEVIN BV
VERMEER GROND EN WEGEN BV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gebr Van Kessel Bv, IFCO FUNDERINGSEXPERTISE BV, KONINKLIJKE WEGENBOUW STEVIN BV, VERMEER GROND EN WEGEN BV filed Critical Gebr Van Kessel Bv
Priority to EP97929601A priority Critical patent/EP0910709B1/fr
Priority to DE69710464T priority patent/DE69710464T2/de
Priority to DK97929601T priority patent/DK0910709T3/da
Publication of WO1998002616A1 publication Critical patent/WO1998002616A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/02—Improving by compacting
    • E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains

Definitions

  • the invention relates to a method of consolidating watery ground, in particular to the forced consolidation of relatively impermeable, compressible soil strata.
  • the accelerated drainage of clay and peat strata is known by firstly providing vertical drainage channels therein and then subjecting these layers to a load. The load applied exerts an excess pressure on the interstitial water in the clay or peat strata.
  • the vertical drainage channels ensure a considerably improved discharge of the groundwater.
  • This drainage method also means that water in the ground can flow in the horizontal direction towards the drainage channels, as a result of which optimum use is made of any stratification in the soil structure.
  • the permeability of the ground in the horizontal direction is as a rule greater by a factor of 10 than that in the vertical direction.
  • a horizontal drainage layer can be arranged at ground level above the top of the vertical drainage channels.
  • This drainage layer generally comprises a layer of sand having a thickness of, for example 0.3 metres or more.
  • This layer absorbs the groundwater which leaves the ground via the drainage channels.
  • a specific embodiment is that in which this layer is covered by a film whose edges are buried in the ground to below the groundwater table.
  • a drawback of the above-described consolidation method is that it is not possible to achieve an underpressure in the drainage layer situated at the surface of greater than 6-7 metres water column.
  • the underpressure in the water-saturated ground decreases by 0.1 bar per metre of depth, so that at a depth of 6 metres atmospheric pressure prevails.
  • gas and/or air is released at many locations in the ground owing to the pressure reduction in the groundwater. This formation of gas means that the volume to be pumped off increases, which impairs the efficiency of the water removal system.
  • a further drawback of the above-described method is that all the vertical drainage channels are connected together via the drainage layer, so that the system as a whole is extremely sensitive to leakage. It is therefore frequently difficult in practice to maintain the desired underpressure for a relatively long period of time. The entire system is sensitive to a single leak. This is even more important when it is considered that the vertical drainage channels in the conventional methods are used in numbers of 2000 to 10,000 per hectare.
  • a further object of the present invention is to provide a method of this kind in which a relatively small number of easy-to-operate pumps can be used, which pumps are relatively unsusceptible to maintenance, are not adversely affected by the groundwater level, and can be used at a great number of different depths.
  • the method according to the invention comprises the following steps: - introducing a drainage element into the ground to below the groundwater table,
  • this pump can be arranged at any desired position in the drainage element.
  • the groundwater is pressed upwards instead of being sucked upwards.
  • a pump according to the invention such as a venturi pump
  • an underpressure of at least 9 metres water column can be generated. If the venturi pump according to the invention is placed at a depth of 5 metres, the effect for a groundwater level which lies one metre below ground level is an underpressure of 13 metres water column In the known methods, an underpressure of not more than one metre water column is obtained. Due to the fact that a great pressure difference can be generated using the venturi pump according to the present invention, sufficient compression of the ground can be achieved within a relatively short time.
  • the water level is lowered by using the pump according to the invention Due to the lowering of the groundwater level, the load increases owing to the ground coming above water level and the absence of the upwards force of the groundwater thereon, as a result of which consolidation is achieved.
  • Drainage element is intended to mean a structure which is arranged in the ground and has a greater porosity than the surrounding soil stratum.
  • the drainage element may, for example, comprise a shaft having a diameter of, for example, 10 cm or more. This shaft may be filled with sand or another relatively porous material, such as for example rubble or gravel.
  • the drainage element may also be formed by a vertical wall made of relatively permeable material and having a length of several hundred metres, a depth of between 1 and 7 metres and a width of between 5 cm and 25 cm. A strip of filter cloth which is inserted vertically into the ground may also be used as drainage element.
  • the drainage element may, for example, comprise only a tubular element containing the pump according to the invention. With this type of soil, the groundwater level will fall and, in view of the low compressibility, a small degree of consolidation will be obtained
  • Pumps operating with a pumping liquid are of extremely simple design, since they do not comprise any mechanically moving parts and can be of relatively small size, such as for example having a diameter of about 10 centimetres and a length of about 20 centimetres.
  • pumps of this kind are relatively unsusceptible to maintenance and can easily be arranged in, for example, a relatively tight drainage shaft or a relatively narrow tubular element, bends in the latter forming no obstacle to the introduction.
  • it is possible using pumps of this kind to achieve a relatively high reduction in pressure which may be 50% higher than is usual with conventional motor-driven pumps. This results in greater efficiency ad the desired degree of consolidation can be achieved more rapidly than in the known methods or a higher degree of consolidation can be achieved in the same time.
  • the pump is formed by a venturi pump with a pump capacity of at least 1 m 3 per hour, preferably between 1 and 10 m 3 per hour.
  • both gas and the groundwater around the pump are removed via the discharge line by being entrained with the pumping liquid.
  • the pump will be used firstly to pump off gas which lies above the water In a following stage, a large amount of gas and a small amount of water is pumped off and finally a mixture of gas and water is pumped away, since gas is continuously released as the underpressure rises and is continuously entrained.
  • the method according to the invention is particularly suitable for quickly making building sites and traced-out roads suitable for construction and for ensuring that on completion the subsidence of the ground level which is still to be expected is as small as possible, and preferably negligible.
  • cables and pipes, but also railways and paved or asphalted surfaces or roads, streets, squares, pavements, gardens and the like will no longer be subject to any settlement once a treated area has been completed. This results in a considerable saving on maintenance costs.
  • Using the consolidation method according to the invention also makes it possible to consolidate strips of ground where streets and/or gardens are situated while carrying out building work around these strips which are being consolidated. Since the building work on the compressible ground involves driving piles, consolidation will not be possible at the location of the building work itself
  • An essentially airtight seal may be arranged at the feed opening of the drainage element, such as a sand-filled shaft, or a tubular element. If a tubular element is arranged in the ground with a closed tube wall and a sealed tube end which is positioned in the ground and is provided with perforations, which tubular element contains the pump, the seal can be formed by a cap over that end of this tubular element which is situated above the ground A cap of this kind placed over the blind part of the said tubular element is essential for obtaining sufficient underpressure .
  • a multiplicity of drainage elements is arranged in the ground so as to achieve effective drainage.
  • each drainage element surrounds a respective tubular element in which a pump is positioned It is thus possible, for example, to consolidate a strip of 100 by 5 metres using one drainage element and one pump according to the invention arranged therein, so that only 20 drainage elements and pumps are required per hectare of land. For a settlement rate of 30 mm/day, it is then necessary to discharge 15 m 3 of water/gas under atmospheric pressure. Together with this amount there is also leakage water which flows in through the ground from the sides or the bottom and/or precipitation on the surface of the ground. A pump capacity of 1-3 m 3 per hour is sufficient to consolidate the ground.
  • each drainage element is provided with its own pump, this has the advantage that in the event of an excess of gas being sucked in by one pump, for example due to the fact that the seal has developed a leak or a pump is malfunctioning, this has no adverse effect on the other pumps, which are independent thereof.
  • each pump is provided with a monitoring device for determining the pressure difference across the respective pump. As a result it is possible to check efficiently that this pump is not sucking up an excess of air and that there is no need to replace the seal.
  • Figure 1 shows a diagrammatic depiction of a pump according to the invention placed in the subsoil
  • Figure 2 shows a diagrammatic detailed depiction of a venturi pump according to the invention.
  • Figure 1 shows a subsoil 1 having a groundwater table 3.
  • a tubular element 5 with a vertical section 6 and a horizontal section 7 is arranged in the subsoil 1.
  • the tube 5 is of a "blind" design in the vertical section 6 and is essentially impervious to water and air.
  • the blind section of the tube 5 may, for example, be 25 m long. That end of the tube 5 which is positioned in the subsoil, having a diameter of, for example, 10 cm, is provided with perforations 8, through which the groundwater can penetrate into the tube 5.
  • a venturi pump 9 having a flexible feedline 11 and a flexible discharge line 12 is positioned in the tube 5.
  • a pumping liquid such as for example water
  • a centrifugal pump 13 is fed through the feed-line 11, via a centrifugal pump 13, to the venturi pump 9 at a pressure of a number of atmospheres, for example 10 atmospheres excess pressure. Due to the pumping liquid, an underpressure is formed on the feed side of the venturi pump 9 and liquid and gas are entrained by the pumping liquid via the discharge line 12 at a lower pressure and higher flow rate compared to the feedline 11.
  • the venturi pump 9 it is possible to remove between 1 and 10 in 3 of water and/or gas per hour from the subsoil 1.
  • the tube 5 is situated in a drainage element 13
  • the drainage element 13 extends, for example, to a depth of 7 metres below the surface of the ground 1 and has a dimension perpendicular to the plane of the drawing of about 25-30 centimetres
  • the drainage element 13 is filled, for example, with a porous material such as sand or rubble
  • a number of drainage elements 13 are arranged parallel to one another in the subsoil at a mutual distance of, for example, 5 metres, so that, for example, each strip of 100 x 5 m comprises a drainage element
  • Each drainage element is provided with its own venturi pump 9 It is also possible to arrange a plurality of venturi pumps 9 in a single drainage element, for example at both ends thereof
  • the water from the subsoil 1 will flow to the closest drainage elements 13 and is discharged via the perforations 8 in the tube 5
  • a seal 15, in the form of, for example, a plastic cap, is arranged at the top of the tube 5, preventing air from being able to pass to
  • the above-described drainage structure is used m relatively impervious subsoils, such as clay or peat.
  • the drainage method which involves placing a venturi pump in a drainage shaft or tube can also be used for subsoils of greater permeability, such as for example sand. In this case, it is not necessary to use a further drainage element in addition to a tubular drainage element.
  • FIG. 2 shows a diagrammatic depiction of a venturi pump 9 according to the present invention.
  • the pumping liquid B is fed through an opening 19 in an internal tube 20.
  • the pumping liquid which passes out of the internal tube 20 at high speed via a nozzle 22, results in an underpressure at the feed opening 17 of the pump 9.
  • groundwater and gas present around the pump are sucked into the feed opening 17 via the direction of the arrow A.
  • the pumping liquid B and the gas and/or water A sucked in are discharged via the discharge opening 18 of the pump.
  • a suitable venturi pump has a length of 320 millimetres and a maximum width of 70 millimetres. Pumps of this kind are produced by Grundfoss under model number 900216.
  • the maximum discharge of the pumps is 2.5 m 3 /hour.
  • the connections for the feedline 11 and the discharge line 12 are oriented next to one another in the same direction.
  • the feed opening 17 lies on the opposite side.
  • the venturi pump can be inserted, with the feed opening 17 at the front, into a tube with an internal diameter of 10 cm
  • an acid can be added to the pumping liquid B for dissolving the iron present in the groundwater, so that the venturi pump 9, the feedline 11 and discharge line 12 do not become blocked by this iron.
  • Some of the discharged water A + B can be reused as pumping liquid B.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Structural Engineering (AREA)
  • Agronomy & Crop Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Soil Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)

Abstract

La présente invention a pour objet un procédé de consolidation d'un sol aqueux, en particulier un sol aqueux relativement imperméable. Une pompe (9) alimentée en liquide de pompage est disposée dans un élément drain (13) placé au-dessous du niveau de la nappe souterraine. L'eau souterraine et/ou le gaz présents dans le sous-sol sont évacués au moyen du liquide de pompage, ce qui permet d'obtenir une consolidation très rapide et très efficace du sol. La pompe (9) est dotée de préférence d'un dispositif venturi. L'élément drain (13) peut inclure une paroi de sable orientée verticalement dans laquelle est placé un élément tubulaire contenant la pompe.
PCT/NL1997/000405 1996-07-12 1997-07-11 Procede de consolidation d'un sol aqueux Ceased WO1998002616A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP97929601A EP0910709B1 (fr) 1996-07-12 1997-07-11 Procede de consolidation d'un sol aqueux
DE69710464T DE69710464T2 (de) 1996-07-12 1997-07-11 Verfahren zur konsolidierung von wasserhaltigem boden
DK97929601T DK0910709T3 (da) 1996-07-12 1997-07-11 Fremgangsmåde til pakning af vandholdig jord

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1003584A NL1003584C2 (nl) 1996-07-12 1996-07-12 Werkwijze voor het consolideren van waterhoudende grond.
NL1003584 1996-07-12

Publications (1)

Publication Number Publication Date
WO1998002616A1 true WO1998002616A1 (fr) 1998-01-22

Family

ID=19763199

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NL1997/000405 Ceased WO1998002616A1 (fr) 1996-07-12 1997-07-11 Procede de consolidation d'un sol aqueux

Country Status (5)

Country Link
EP (1) EP0910709B1 (fr)
DE (1) DE69710464T2 (fr)
DK (1) DK0910709T3 (fr)
NL (1) NL1003584C2 (fr)
WO (1) WO1998002616A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6655873B2 (en) 2000-10-04 2003-12-02 Boskalis Westminster, Inc. Method and apparatus for consolidating earth strata

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1008617C2 (nl) 1998-03-17 1999-09-20 Hollandsche Betongroep Nv Werkwijze voor het consolideren van een waterhoudende grondlaag, zoals een klei- of veenhoudende laag.
NL1009792C1 (nl) * 1998-03-17 1999-09-20 Hollandsche Betongroep Nv Werkwijze voor het consolideren van een voor vloeistof slecht doorlatende waterhoudende grondlaag, bijvoorbeeld een klei- of veenhoudende laag.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4927292A (en) * 1989-03-17 1990-05-22 Justice Donald R Horizontal dewatering system
FR2663373A1 (fr) * 1990-06-18 1991-12-20 Cognon Jean Marie Procede et dispositif pour etablir une depression dans une zone de terrain permeable isolee de l'atmosphere par une membrane etanche.
WO1992018702A1 (fr) * 1991-04-09 1992-10-29 Bayer Aktiengesellschaft Elements de drainage fabriques par assemblage colle, procede de fabrication et application
EP0677616A1 (fr) * 1994-04-14 1995-10-18 Koninklijke Wegenbouw Stevin B.V. Procédé de compactage et de consolidation du sol sous-marin

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4927292A (en) * 1989-03-17 1990-05-22 Justice Donald R Horizontal dewatering system
FR2663373A1 (fr) * 1990-06-18 1991-12-20 Cognon Jean Marie Procede et dispositif pour etablir une depression dans une zone de terrain permeable isolee de l'atmosphere par une membrane etanche.
WO1992018702A1 (fr) * 1991-04-09 1992-10-29 Bayer Aktiengesellschaft Elements de drainage fabriques par assemblage colle, procede de fabrication et application
EP0677616A1 (fr) * 1994-04-14 1995-10-18 Koninklijke Wegenbouw Stevin B.V. Procédé de compactage et de consolidation du sol sous-marin

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6655873B2 (en) 2000-10-04 2003-12-02 Boskalis Westminster, Inc. Method and apparatus for consolidating earth strata
US6991406B2 (en) 2000-10-04 2006-01-31 Dirk Albertus Bodegom Method and apparatus for consolidating earth strata

Also Published As

Publication number Publication date
NL1003584C2 (nl) 1997-06-06
DE69710464T2 (de) 2002-10-02
DK0910709T3 (da) 2002-03-25
EP0910709B1 (fr) 2002-02-13
DE69710464D1 (de) 2002-03-21
EP0910709A1 (fr) 1999-04-28

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