EP1064432A1 - Procede de consolidation de couches de terrain a faible permeabilite - Google Patents

Procede de consolidation de couches de terrain a faible permeabilite

Info

Publication number
EP1064432A1
EP1064432A1 EP99910865A EP99910865A EP1064432A1 EP 1064432 A1 EP1064432 A1 EP 1064432A1 EP 99910865 A EP99910865 A EP 99910865A EP 99910865 A EP99910865 A EP 99910865A EP 1064432 A1 EP1064432 A1 EP 1064432A1
Authority
EP
European Patent Office
Prior art keywords
pipe
water
line
trench
filter
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.)
Granted
Application number
EP99910865A
Other languages
German (de)
English (en)
Other versions
EP1064432B1 (fr
Inventor
Gérard Louis Marie VAN DER SCHRIECK
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.)
Hollandsche Beton Groep NV
Original Assignee
Hollandsche Beton Groep NV
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
Priority claimed from NL1008617A external-priority patent/NL1008617C2/nl
Application filed by Hollandsche Beton Groep NV filed Critical Hollandsche Beton Groep NV
Publication of EP1064432A1 publication Critical patent/EP1064432A1/fr
Application granted granted Critical
Publication of EP1064432B1 publication Critical patent/EP1064432B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • E02D3/106—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains by forming sand drains containing only loose aggregates
    • 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 for consolidating a water-containing layer of soil with limited liquid permeability, for example a clay- or peat-containing layer, comprising: positioning at least one dewatering element in the soil, which element comprises a trench or hole which is filled with a material with good water permeability, such as sand, in which trench or hole there is a pipe which has an impermeable wall and which is connected to a filter element, - and raising the groundwater which has passed into the pipe via the filter to above ground level by means of a separate riser pipe, which riser line is situated at least partially in the said pipe.
  • a dewatering element in the soil, which element comprises a trench or hole which is filled with a material with good water permeability, such as sand, in which trench or hole there is a pipe which has an impermeable wall and which is connected to a filter element, - and raising the groundwater which has passed into the pipe via the filter to above ground level by means of a separate riser pipe, which rise
  • a method of this nature is known from NL-A- 1003584.
  • a venturi pump is positioned near the bottom of the trenches. This pump is connected to ground level by means of a liquid feed line and a liquid discharge line. Groundwater and pump water are discharged simultaneously.
  • the object of the invention is to avoid these drawbacks, and to this end the method mentioned in the preamble is characterized in that a non-return valve is connected to the filter on the pipe, and in that the said riser line is a suction line which is connected to a suction source positioned above or in the vicinity of ground level.
  • suction line has a connection, which can be shut off by a shut-off valve, to a suction source which is designed as a vacuum tank connected to a vacuum pump, which vacuum tank is connected, via a line with pump, to a line which opens out in or above a water 2 collection tank.
  • the said pipe may be placed in communication, via lines and shut-off valves, with either a suction source or the atmosphere or a pressure source.
  • the space inside the said pipe is divided into two chambers by a diaphragm, the first chamber being in communication, via a line, with means for intermittently placing the said chamber in communication with a suction source, the atmosphere or a pressure source, and the second chamber being connected to the said filter on the underside, via the said non-return valve, and being placed in communication with the suction line on the top side, via a non-return valve.
  • the said diaphragm is preferably in the form of a bag, the interior of which forms the said second chamber.
  • a drainage pipe to be arranged in the said trenches or holes and for the said water- collection pipe to be placed with the water inlet part in the said drainage pipe, in a removable and replaceable manner.
  • the drainage pipe preferably comprises flexible material and has a part which projects approximately as far as or above ground level and a part which extends essentially along the length of the trench in the ground.
  • the drainage pipe will be surrounded by filter material, as is customary.
  • a sheet may be placed over the top surface of the trench or shaft which is filled with water-permeable material, it 3 being possible to place the bottom surface of the said sheet in communication with a suction source via a line with a valve.
  • EP-A-0,608,928 describes a method for consolidating a layer of soil with limited liquid permeability, in which method vertical drainage pipes which are provided with perforations are inserted into the layer of soil with limited permeability, which drainage pipes are surrounded by filter membranes.
  • a riser line in the form of a suction line which is connected to a suction pump positioned above ground level, is fitted into the said drainage pipes.
  • the bottom of the pipe is closed off by a cover or tight plug and a plug of expanded plastic material is arranged at a short distance from the top of the pipes.
  • a line for supplying compressed air opens into the drainage pipes. In this known method, there are no trenches filled with sand or similar material dug in the soil.
  • the drainage pipes are provided with perforations over their entire height, so that neither a filter at the bottom of the pipes nor a non-return valve are present. If sand-filled pipes were to be used, the method would not work in combination with the perforations in the pipes. The pressure reduction would then spread across the spaces between the grains of sand and, in the event of compressed air being blown in, this compressed air would disappear into the sand via the perforations. The absence of sand- filled trenches means that the flow of water into the pipes will be slight.
  • Figure 1 shows a cross section perpendicular to a sand-filled trench which is arranged in the soil and which accommodates dewatering means and also has water- raising features positioned at ground level.
  • Figure 2 shows a cross section through the trench perpendicular to the cross section of Figure 1.
  • Figure 3 shows a second embodiment in cross section perpendicular to a sand-filled trench which is dug in the soil and has dewatering means.
  • Figure 4 shows a cross section in the longitudinal direction of a trench dug in an area of land which is to be consolidated, in a third alternative embodiment.
  • Figure 5 shows a cross section through the area of land which is to be consolidated, transverse to the trench in the embodiment in accordance with Figure 4.
  • parallel trenches 1 4 are dug in the clay or peat soil at intervals of, for example, 2 to 3 metres. Only one of these trenches 1 is shown.
  • the trenches are filled with sand or another water-permeable material.
  • the top layer is replaced or covered by a layer of sand 2.
  • a pipe 3 is positioned in each trench 1, surrounded by the sand, with a filter 4 attached to its underside.
  • a wall 5 with an opening which can be closed off by a nonreturn valve 6 is positioned between the filter 4 and the pipe 3.
  • the remaining part of the pipe 3, runs optionally via a horizontal part (as shown in Figure 2), to above ground level and ends at an end piece 7.
  • a suction line 8 extends from a point which lies just above the non-return valve 6 to as far as the end piece 7, and from there, via an opening in the end piece 7, to a water collection tank 9.
  • a vacuum tank 10 in which the vacuum is automatically maintained within selected limits by a vacuum pump 11 , is placed in communication with the suction line 8 via a line 12 with a shut-off/non-return valve 13 and via a line 14 with a drainage pump 15. If drainage pump 15 is not operating, line 14 is closed off.
  • the end piece 7 is in communication with the vacuum vessel 10 via line 16 with the shut-off valve 17 and line 18.
  • a manifold 19 is fitted in the line 16 below the shut-off valve 17, and a compressed-air line 20 with shut-off valve 21 and a line 22 which opens out into the outside air and has shut-off valve 23 are connected to this manifold 19.
  • the line 18 which is connected to the vacuum tank passes through to the bottom surface of a covering sheet 26 which is positioned above the layer of sand arranged on the layer of clay or peat.
  • a shut-off valve 24 is arranged in the line 18.
  • a shut-off valve 25 is positioned in the suction line 8 between the lines 12 and 14. The installation operates as follows:
  • the normal groundwater level is indicated in Figure 1 by P.
  • the shut-off valve 13 is open and the shut-off valve 17 is closed.
  • the pump 11 generates a vacuum in the vacuum tank 10.
  • the water present in the pipe 3 is sucked up via the suction line 8 and is discharged into the tank 9 via line 12 and the open valve 13, with the valve 25 in the closed position.
  • the water falls to the level Q, the difference in height between the levels P and Q corresponding to the vacuum in the vacuum tank 10. If too much water still remains in the pipe 3, the water level in the pipe 3 can be lowered to the level R by allowing compressed air to flow into the pipe 3 via the open line 20, the shut-off 5 valve 21 and the line 16.
  • Figure 2 shows that the pipe 3 has a long horizontal section 3A.
  • the non- return valve 6 is of flap design. This horizontal section forms a buffer.
  • shut-off valve 24 By opening the shut-off valve 24, air is sucked out beneath the sheet 26. The result is that the pressure is reduced (for example by 6 metres water column) to as far as the bottom of the trench 1. The load on the subsoil is increased by approximately the same pressure, resulting in accelerated consolidation. The trench 1 will then be filled more quickly with water which is released from clay or peat soil by consolidation. In this process, there is a risk of the water level in the pipe 3 rising to above the level P, since a considerably increased load on the soil is involved.
  • the liquid level in the pipe 3 can be lowered by sucking out water, for which purpose atmospheric air can be admitted into the pipe 3 via the shut-off valve 23 or compressed air can be admitted via the shut-off valve 21. As soon as the water level in the pipe has fallen back to the desired level, the pressure can be reduced by suction.
  • the system can function unmanned by automatically switching various shut- off valves and flaps within specific time intervals.
  • the pipe 3 together with the suction line 8 is installed in a plastic drain which is known per se and functions as a filter 4.
  • a plastic drain which is known per se and functions as a filter 4.
  • An advantage of this embodiment is that components of the system according to the invention which lie in the soil can be retrieved and reused.
  • the embodiment in accordance with Figure 3 differs from the embodiment in accordance with Figures 1 and 2 in that that part of the suction line 8 which is situated in the pipe is replaced by an elongate diaphragm 30, which is connected to the filter 4 by means of non-return valve 6 and is connected to the suction line 8 via the non-return 7 valve 31.
  • Figures 4 and 5 show in a more or less diagrammatic manner that a number of drainage trenches 1 have been dug, at intervals of, for example, 2 to 3 m, in an area of land which comprises a layer of soil with limited water permeability, such as peat or clay, and which is to be consolidated by settling, in which drainage trenches a water- collection hose 3 is placed, with a non-return valve 6 at its bottom end, optionally followed by a filter which can filter water flowing in.
  • a number of drainage trenches 1 have been dug, at intervals of, for example, 2 to 3 m, in an area of land which comprises a layer of soil with limited water permeability, such as peat or clay, and which is to be consolidated by settling, in which drainage trenches a water- collection hose 3 is placed, with a non-return valve 6 at its bottom end, optionally followed by a filter which can filter water flowing in.
  • the other end 7 of the water collection hose 3 extends to above ground level, and in the manner described above a line 16 is connected to the end 7, which line may be connected, via shut-off valves, to a suction line, a compressed-air line or a line which opens out to the atmosphere.
  • a water suction hose 8 which is connected in the manner described above to a vacuum tank (not shown) and which opens out above a water collection tank (not shown), is situated in the water collection hose 3.
  • the water collection hose 3 is arranged in a flexible drainage pipe 32 which is positioned in the trench 1 before this trench is filled with sand or another water- permeable material.
  • the drainage pipe 32 will have a filter material, such as coir or a nonwoven, wound around it.
  • the flexible drainage pipes 32 will extend over substantially the entire length of the trenches.
  • a sheet 26 may be laid over the surface of the soil to be consolidated.
  • the suction hose 8 which is connected to a vacuum source is used to suck the water out of the hose 3 and guide it into a tank.
  • the water level in the water collection hose 3 falls to a level which corresponds to the vacuum generated by the suction source.
  • the water level in the water collection pipe 3 can be lowered further by connecting the line 16 to a compressed-air source, with the valve 6 closed and the remaining water being discharged via the hose 8 by means of the excess pressure.
  • the lowest water level has been reached (just below the bottom limit of the horizontal section of the water collection hose 3)
  • the supply of compressed air is stopped and the hose 8 is again connected to the vacuum source.
  • Water can be admitted back into the water collection hose 3 via the non-return valve 6.
  • vacuum and compressed air are used intermittently. The possibility of using atmospheric pressure instead of compressed air is not ruled out.
  • the drainage capacity of the system with a continuous flexible drainage pipe over the length of the draining body of sand is many times greater than with the system according to Figures 1 to 3 inclusive.
  • the said area is surrounded by a water-replacing wall 33, comprising a trench which is filled with sand or another water-permeable material and is fed with water, for example by means of a make-up ditch 34.
  • the groundwater level is indicated by dashed lines in Figure 2 and in the vicinity of the wall 33 rises steeply up to the water level in the ditch 34. There is no reduction in the groundwater level outside the area which is to be consolidated. There is no risk of subsidence or damage to piled foundations in the immediate vicinity of that area.
  • groundwater can be raised from 9 depths in excess of approx. 8 m water column. Reaching the lowest water level in pipe 3 can be monitored by measuring the water discharged into the tank 9.
  • Compressed-air facilities are inexpensive and the system can be fitted in plastic drains, resulting in a reduction in price.

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

Pour consolider une couche de terrain contenant de l'eau présentant une perméabilité limitée aux liquides, par exemple une couche contenant de l'argile ou de la tourbe, on place au moins un élément d'assèchement dans le sol, cet élément d'assèchement comprenant un sillon ou un trou (1) qui est rempli d'une matière présentant une bonne perméabilité à l'eau, telle que du sable, un tuyau (3) doté d'une paroi imperméable étant placé dans le sillon ou le trou et relié à un élément de filtration. A l'aide d'une conduite montante séparée (8; 8, 30) l'eau de rétention qui est entrée dans le tuyau (3) par le filtre (4) est remontée au-dessus du niveau du sol, cette conduite montante (8; 8, 30) étant située au moins partiellement dans ledit tuyau (3). Un clapet de non-retour (6) est couplé au filtre (4) situé sur le tuyau (3), et la conduite montante (8; 8, 30) comprend une tubulure d'aspiration qui est couplée à une source (10, 11) d'aspiration placée au-dessus du niveau du sol ou à proximité de ce dernier.
EP99910865A 1998-03-17 1999-03-16 Procede de consolidation de couches de terrain a faible permeabilite Expired - Lifetime EP1064432B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
NL1008617 1998-03-17
NL1008617A NL1008617C2 (nl) 1998-03-17 1998-03-17 Werkwijze voor het consolideren van een waterhoudende grondlaag, zoals een klei- of veenhoudende laag.
NL1009792A NL1009792C1 (nl) 1998-03-17 1998-08-03 Werkwijze voor het consolideren van een voor vloeistof slecht doorlatende waterhoudende grondlaag, bijvoorbeeld een klei- of veenhoudende laag.
NL1009792 1998-08-03
PCT/NL1999/000141 WO1999047756A1 (fr) 1998-03-17 1999-03-16 Procede de consolidation de couches de terrain a faible permeabilite

Publications (2)

Publication Number Publication Date
EP1064432A1 true EP1064432A1 (fr) 2001-01-03
EP1064432B1 EP1064432B1 (fr) 2002-07-10

Family

ID=26642775

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99910865A Expired - Lifetime EP1064432B1 (fr) 1998-03-17 1999-03-16 Procede de consolidation de couches de terrain a faible permeabilite

Country Status (5)

Country Link
EP (1) EP1064432B1 (fr)
AU (1) AU2963099A (fr)
DE (1) DE69902088T2 (fr)
NL (1) NL1009792C1 (fr)
WO (1) WO1999047756A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2395103B (en) * 2000-09-08 2004-12-08 Permavoid Ltd Column forming apparatus
FR2853055A1 (fr) * 2003-03-31 2004-10-01 Denis Alonso S A Methode de tubage d'un forage destine au minage et contenant de l'eau
CN102162253B (zh) * 2011-05-07 2012-09-19 山东新城建工股份有限公司 深基坑埋管降水施工方法
FR3009005B1 (fr) * 2013-07-26 2015-07-24 Soletanche Freyssinet Systeme et procede pour assecher des sols humides.
JP6304813B2 (ja) * 2014-04-28 2018-04-04 五洋建設株式会社 飽和地盤の締め固め工法
CN108751639B (zh) * 2018-07-26 2021-06-11 广州市盛洲地基基础工程有限公司 一种污泥脱水固化处理方法及装置
CN109162272B (zh) * 2018-11-02 2024-04-26 交通运输部天津水运工程科学研究所 一种软弱土变压力抽真空加固装置
CN114991191B (zh) * 2022-05-30 2023-06-09 中建生态环境集团有限公司 一种复式真空负压降水抽水一体井管

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2627202B1 (fr) * 1988-02-15 1992-04-17 Menard Soltraitement Procede et dispositif de consolidation de terrains
US4927292A (en) * 1989-03-17 1990-05-22 Justice Donald R Horizontal dewatering system
FR2663373B1 (fr) * 1990-06-18 1993-05-28 Cognon Jean Marie Procede et dispositif pour etablir une depression dans une zone de terrain permeable isolee de l'atmosphere par une membrane etanche.
BE1006637A3 (nl) * 1993-01-25 1994-11-03 Verstraeten Funderingstech Bv Werkwijze voor het versneld konsolideren van een terrein.
NL1003584C2 (nl) * 1996-07-12 1997-06-06 Kessel B V Geb Van Werkwijze voor het consolideren van waterhoudende grond.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9947756A1 *

Also Published As

Publication number Publication date
EP1064432B1 (fr) 2002-07-10
DE69902088D1 (de) 2002-08-14
DE69902088T2 (de) 2003-03-20
WO1999047756A1 (fr) 1999-09-23
AU2963099A (en) 1999-10-11
NL1009792C1 (nl) 1999-09-20

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