FR2648839A1 - FOUNDATION PILES, METHODS, TOOLS AND MACHINES FOR CONSTRUCTING THESE PILES - Google Patents

Abstract

The invention relates to foundation piles and methods, tools and machines for the construction of these piles. A pile according to the invention comprises a collaborating casing 1 which is composed of prefabricated tubular elements 1a, 1b, etc., in reinforced concrete or prestressed concrete, which have an external diameter of between 300 and 500 mm and a thickness of the order of 80 to 100 mm, which are assembled end to end by connecting rods 3 sealed with resin and which comprise radial channels 2. It also comprises a filling 4 of concrete, cement grout, sand. .. or which is injected under pressure into the surrounding land through the channels 2. To drive the casing elements into the ground, an auger is used which passes inside the casing and which carries, at its end, a tool. havage. One application is the construction of foundation piles for common civil engineering works and buildings.

Description

Foundation piles, processes. tools and machines for construction

said piles.

DESCRIPTION

  The present invention relates to new foundation piles as well as processes. tools and machines for the

construction of these piles.

  The technical sector of the invention is that of construction

  stakes intended to serve as a foundation for everyday works.

  In the field of common pile foundations. that is to say, piles to support loads between 400 and 2000

  K.N. we use to this day. two categories of piles.

  A first category is that of micropiles injected

a diameter less than 200 m.

  Micropiles are obtained by drilling techniques

  used in the mining or oil fields.

  In a first phase, a drill is drilled with a drill bit and

  this drilling is equipped with a perforated casing.

  In a second phase. a cement grout is injected into the casing and this grout passes through the perforations of the casing.

  casing and penetrates the surrounding lands.

  Thanks to this injection, the micropiles have the advantage

  a very good friction between the pile and the ground.

  By cons, they have the disadvantage of low inertia.

  hence risk of buckling and low resistance to horizontal forces. It is not feasible to economically construct piles with a diameter greater than 200 m by bit drilling techniques. which would entail the construction of tools for

very expensive drilling.

  A second category of common piles are the traditional driven and cast piles with a diameter greater than or equal to 0.4. A machine is known, used for the construction of traditional piles, which has a vertical auger and is moved along a vertical axis and is driven in rotation & slow speed, so that it enters the ground as a corkscrew. Once the auger is pushed down to the bottom level of a pile. one pulls up with jacks while sending a concrete grout to

  through the hollow shaft of the auger.

  As the auger rises, it carries with it a cylindrical core of ground in the manner of a corkscrew and the vacuum that is created is filled with concrete grout. This technique makes it possible to obtain piles of large diameter that are not likely to flare up. However, it presents difficulties of implementation in unstable ground. In addition, since the concrete is poured in place as the core is removed from the ground, it is not

  it is not possible to control the quality of the concrete filling of the well.

  The friction characteristics between the soil and a pile

  traditional are worse than those of the injected piles.

  The numerous disorders that have occurred on traditional piles have led to the need for quality controls and to limit the allowable stresses in cast-in-place concrete at working rates of the order of 5 to 6 MPa, ie less than half of

theoretical work rate.

  The objective of the present invention is to provide new intermediate foundation piles between the micropiles and the traditional piles, which combine the advantages of these, that is to say which allow to set up during digging a reinforced or prestressed concrete casing collaborating with the bearing force of the pile. fill it in whole or in part, using concrete, grout, sand ... o eliminate the risk of landslides or cavities in the filling material, inject a cement grout in the surrounding terrain to improve lateral friction and to obtain piles of sufficient diameter to avoid the risk of buckling and armed piles that are resistant to

horizontal efforts.

  This objective is achieved by means of foundation piles which comprise: a concrete casing, composed of tubular elements made of reinforced concrete or prestressed concrete. having an outer diameter, of the order of 300 to 800 mm and a thickness of about 80 to 150 am, which elements comprise radial channels - and if necessary a cement slurry which forms a core cast on a part of less of the interior of said casing and which is injected under pressure into the surrounding lands through the said

radial channels.

  Advantageously, the prefabricated tubular elements comprise, at their two ends, vertical reservation holes and two superposed elements are assembled end to end by connecting bars. who are engaged in two holes being done

  face and which are sealed with a polymerizable resin.

  A method of construction of a foundation pile according to the invention comprises the following operations: - Factory prefabricated tubular elements of reinforced concrete or prestressed concrete. having an outer diameter of the order of 300 to 800 mm and a thickness of about 80 to 100 mm and having radial channels; - One descends one by one said elements vertically in the ground by havage by means of an auger which is engaged inside the prefabricated elements, which carries at its end a retractable hacking tool and which is rotated at a speed sufficient to evacuate cuttings: - when an element is fully sunk into the soil, the auger is removed and a second tubular element is erected on the first. then we go down the auger inside the two elements and we continue the havage: - and. when the prefabricated casing is in place, the filling is carried out using concrete, grout, sand, or it is put in place therein an inflatable shutter at an intermediate level and injected, in the area located inside the casing and below said shutter, a cement slurry which penetrates the surrounding lands through said radial channels

to form an anchor in the ground.

  A tool for implementing a method according to the invention comprises a vertical shaft which is rotated by a rotary table movable along a vertical m * it and which carries a helical screw forming an auger, and said shaft carries at its end, a foldable cutting tool, which is in a folded position inside a circle having a diameter less than the internal diameter of said prefabricated tubular elements and which, in the working position, has a diameter external superior to the outer diameter

  said prefabricated tubular elements.

  According to a preferred embodiment. the cutting tool comprises a metal blade which is located below the lower end of said helicoidal screw and which pivots about an axis of vertical articulation eccentric with respect to the axis of said auger. The invention results in new foundation piles having

  an outer diameter of the order of 300 mm to 800 mm.

  The piles according to the invention are intermediate between

  micropiles and the traditional piles beaten and molded.

  The piles according to the invention have the following advantages: in unstable ground, the holding of the grounds is ensured by the

  prefabricated concrete elements that function as collaborative casing.

  The piles according to the invention can pass through relatively hard layers of terrain by using a drilling tool comprising

  Destructive cuttings allowing the crossing of these grounds.

  The reinforced concrete tubular elements are prefabricated at the factory and can be prestressed. which ensures a good reliability of

qualities of concrete.

  The concrete filling, cement grout. Sand ... or grout injected under pressure is achieved away from the lost casing. what

  allows a homogeneous filling.

  Eligible working stresses both in the casing

  prefabricated only in the grouting of concrete are 8 MPa.

  The piles according to the invention make it possible to inject cement slurry through the casing into the surrounding lands and to obtain a coefficient of lateral friction of the piles which is two to four times.

  times higher than that of piles beaten or cast in place.

  As a result, the piles according to the invention can support

  an identical unit friction identical to that of the micropile.

  The piles according to the invention can withstand high horizontal forces due to the reinforcements of the prefabricated casing and the

  connecting bars between tubular elements.

  If necessary, the resistance to horizontal forces can be increased by adding a reinforcement in the central part of the pile before filling it with cement grout. It is even possible to pretension the pile by means of a tie

Central put in tension.

  The following description refers to the accompanying drawings which

  represent. without any limiting character. an example of

  realization of a pile according to the invention.

  FIG. 1 is a vertical section of a pile according to

  the invention passing through the zzl axis thereof.

  Figure 2 is an elevational view of a construction site

  construction of a pile according to the invention.

  Figure 3 is a large-scale vertical section of

  the lower end of a pile and the drill bit.

  FIG. 4 is a bottom view of the drilling tool in

  working position and in the folded position.

  FIG. 1 represents a pile intended to serve as a foundation

for a book.

  This pile comprises a casing I which is composed of tubular elements la. lb etc .... reinforced concrete or prestressed concrete which are prefabricated in the factory. Each tubular element has an outer diameter of about 400 minutes, which may vary for example between 300 and 800 mm. a thickness of the order of 80 to 150 mm. an inside diameter of the order of 200 to 600 mm and a length of about 5 to

6 meters.

  Figure 1 shows. for illustration. a pile with two elements la. lb bunk. The number of elements

can be superior.

  The elements la. lb being prefabricated at the factory. are manufactured with care and it is possible to calculate the resistance of the pile taking into account 75% of the maximum rate of stress that the

reinforced concrete can withstand.

  Prefabricated elements la. lb have small radial channels 2 which pass through them and which are distributed

over their entire height.

  The tubular elements la. lb have on their upper edge and on their lower edge, vertical reservation holes which face two by two when two elements are superimposed. High strength steel connecting rods 3 are placed in these holes and sealed with a polymerizable resin to

quick decision.

  The tubular elements la. lb can be sized to withstand the entire load that each pile must support. In some cases, the central section filled with cement slurry may be taken into account to define the load that may be

to support the piles.

  In order to improve the friction of the pile with the surrounding land and to reduce the effort exerted on the lower end of the pile, each stake has. on a part of its height, a cement grout 4 which fills the inside of the casing 1 and which penetrates the land encasing passing through the

small radial canals 2.

  Alternatively, the casing 1 can be filled with cement grout

  on all its height. if that is necessary.

  FIG. 2 represents a pile according to the invention in progress

  depressing a first concrete element la.

  We bring to the site where the piles must be established. tubular elements 1a, 1b prefabricated at the factory and vehicle-mounted drilling equipment 5 which carries a mast 6 shown in phantom in the folded position and in solid lines in position

vertical work.

  The mat 6 has a total height that can correspond to the height of the pile. It can be composed of several sections that are

gradually put in place.

  The sinking equipment includes. in addition. a tool comprising a vertical hollow shaft 7 which is rotated by a rotary table 8 movable along the mat 6 and which carries a helical screw 9 forming an auger and, at its lower end, a cutting tool 10. The diameter external of the via 9 is less than the internal diameter of the prefabricated elements la. lb. To drive a first prefabricated element la in the ground, it is placed vertically on the ground, then engages inside it the auger 9 and the hacking tool 10 which is in the folded position. When the tool 10 comes into contact with the ground. the speed of rotation of the table is increased to reach a speed sufficient for the auger to evacuate the cuttings through the upper end of the element 1a. Under the effect of the centrifugal force and the friction of the ground. the tool 10 automatically occupies an abutment position o its outer diameter is slightly greater than the outer diameter of the element la. so that it digs beneath it a cutting line and that the element gradually sinks into the ground following the tool 10. When a first element was pressed into the ground. the rotation table 8 is turned in the opposite direction. this has the effect of automatically folding the cutting tool 10 whose outer diameter is then less than the internal diameter of the element la and then raises the rotation table and the auger high enough to be able to place a second prefabricated element lb vertically above the first element la. Before setting up element lb. vertical bars 3 are engaged in the vertical holes reserved at the upper end of the element 1a, then the vertical holes reserved at the lower end of the element 1b are nested on these bars and the bars are sealed with a

polymerizable resin.

  The hollow shaft 7 and the auger 9 may be composed of several sections that are assembled end to end as the

casing sinks into the ground.

  Once the casing is in place. we take out the auger. the inside of the casing is cleaned and the concrete is filled. grout or sand. In a variant. we place inside the

  casing 1 one or more inflatable shutters of any known type.

  that we go down to a certain level that we have chosen for

  constitute the head of the anchoring zone of the casing.

  The casing is then injected into the interior space

  under the inflatable shutter a cement slurry sufficiently fluid that it passes through the radial channels 2 of the casing and

  penetrates the strata or fiasures of the surrounding lands.

  This injection of cement grout ensures a good connection between the pile and the ground both from the point of view of the peak force of the pile. only lateral friction of the pile. This injection provides, in addition, a good mechanical connection between the various concrete elements la. lb. Figure 3 is an elevational view of the lower end

of the tool in the cutting position.

  This figure shows a prefabricated prefabricated reinforced concrete element which carries, advantageously. at its lower end, a metal shoe 11 having a cylindrical skirt 12 which surrounds the outer periphery of the element la and a frustoconical skirt 13 which diverges downwards. The shoe 11 is optional. It facilitates the gravity descent movement of the casing and facilitates the

  folding of the cutting tool when raising the auger.

  FIG. 3 shows the hollow shaft 7 which carries at its periphery a helical screw 9 forming an auger for

  waste disposal upwards.

  The lower end of the hollow shaft 7 carries fixed peaks

  14, distributed on its periphery which digs in the ground a

  hole having a diameter slightly greater than the diameter of the shaft 7.

  A little above its lower end, the shaft 7 carries a fixed metal blade 15 whose outer diameter is

  substantially equal to the outer diameter of the helical screw 9.

  Advantageously, the blade 15 is helical and it extends

helical screw 9.

  Advantageously. the leading edge of the blade 15 is equipped with

peaks 15a.

  Between the lower end of the helical screw 9 and the fixed blade 15 is mounted a cutting tool 10 having a blade

  16 whose leading edge 17 has peaks 18.

  The blade 16 is articulated around a vertical axis 19 which is

  eccentric to the axis zzl of the shaft 7.

  Advantageously, the blade 16 is slightly helical for

  facilitate the evacuation of cuttings.

  FIG. 4 is a view from below of the lower end of the tool on which is represented in full lines the working position of the cutting tool 10 and in dashed position

folded of this same tool.

  This figure shows the eccentric axis 19 around which the blade 16 of the cutting tool pivots. It can be seen that this blade 16 has the general shape of a crown portion which is delimited by an outer circular arc 161 whose diameter is equal to the external diameter of the helical screw 9 and by an internal circular arc 162. The diameter is equal to the outer diameter of the hollow shaft 7. The two arcs 161 and 162 are parallel. They extend on about a semicircle. They have a common center O which is located at a distance from the pivot axis 19 equal to the eccentricity e of the axis 19 with respect to the axis zzl of the shaft 7. so that the center 0 is moves on a circle centered on

the axis 19 and passing through the axis zzl.

  When the cutting tool 10 is in the folded position shown in dotted lines, the inner edge 162 envelops half of the periphery of the hollow shaft 7 and the outer edge 161 coincides with the projection of the outer periphery of the screw

helicoidal 9.

  When the hollow shaft 7 is rotated clockwise, which is the direction of the land evacuation, the reaction of the land on the peaks 18 and on the blade 16 automatically rotates the latter around it of the axis 19 in the counterclockwise direction. The blade 16 has a heel 20 which is located beyond the axis 19 and which bears against the shaft 7 thus blocking the blade 16 in the working position shown in FIG.

full lines in Figure 4.

  In this position, the peaks 18 and the blade 10 dig into the ground a circular havage limited by a circle C2 which is the circle tangent to the blade 16. The diameter of the circle C2 is slightly greater than the outer diameter of the prefabricated casing elements. When one has finished driving a casing element into the ground, the direction of rotation of the hollow shaft 7 is reversed and the auger is raised. The pivoting blade 16 rubs against the metal shoe 13 or against the lower end of the concrete element 1a in the case where there is no metal shoe and the friction exerts on the blade 16 a thrust that makes it pivot automatically it in a clockwise direction until it is pressed against the shaft 7 in the position shown in FIG.

dotted in Figure 4.

  It can be seen that in this position, the whole of the cutting tool is inside the circle C1 and can therefore go back to

inside the casing.

  The peaks 14, 16, 18 have sharp edges made of a hard material, for example tungsten carbide or any other material commonly used to make tools for drilling or digging rocks. Alternatively, the cutting tool 10 may consist of two blades 16. each occupying half of the circular section Cl in

  folded position, the two axes 19 being diametrically opposed.

2648839.

Claims (9)

  1. Foundation pile, characterized in that it comprises - a concrete casing (1), composed of tubular elements (la, lb) made of reinforced concrete or prestressed concrete, having an external diameter, of the order of 300 to 800 me and a thickness of the order of 80 m to 150 mm. which elements comprise radial channels (2) - and a cement slurry (4) which forms a core cast on at least part of the interior of said casing and which is injected into   the surrounding lands through said radial channels (2).   2. Stake according to claim 1, characterized in that said prefabricated tubular elements (la. at both ends, vertical reservation holes and two elements   superposed are assembled end to end by connecting bars (3).   that are engaged in two holes facing each other and that are sealed by a polymerizable resin.   3. A method of construction of a foundation pile, characterized in that it comprises the following operations: - Factory prefabricated tubular elements (la lb) reinforced concrete or prestressed concrete. having an outer diameter of the order of 300 to 800 mu and a thickness of the order of 80 to 150 mm and having radial channels (2); - one descends one by one said elements (la, lb) vertically in the ground by havage by means of an auger (7, 9) which is engaged inside the prefabricated elements, which carries at its end a cutting tool (10) retractable and which is rotated at a speed sufficient to evacuate the cuttings; when an element (1a) is fully sunk into the ground, the auger (7, 9) is withdrawn and a second tubular element is raised on the first, then the auger (7, 9) is lowered to the interior of the two elements and the havage is continued; - and, when the prefabricated casing is in place, it is filled with concrete, grout or sand ... or is placed in it one or more inflatable shutters at an intermediate level and injecting, into the area inside the casing and below said shutters, a cement slurry (4) which enters the surrounding lands through said channels   radial to form an anchorage in the ground.   4. Tool for carrying out a method according to claim 3 of the type comprising a vertical shaft (7) which is rotated by a rotary table (8) movable along a vertical mit (6) and which carries a helical screw (9) forming an auger, characterized in that said shaft carries at its end a foldable cutting tool, which is in the folded position inside a circle (C1) having a smaller diameter the internal diameter of said prefabricated tubular elements and which, in the working position, an outer diameter greater than the outer diameter of said prefabricated tubular elements, 5. Tool according to claim 4, characterized in that said hacking tool comprises a metal blade (16). which is located below the lower end of said helical screw (9) and which pivots about a vertical hinge pin (19)   eccentric to the axis of said auger.   6. Tool according to claim 5. characterized in that the outer edge (161) and the inner edge (162) of said blade are parallel circular arcs having a common center (0). which is located at a distance (e) from said axis of articulation equal to the distance between the axis of said auger and said articulation axis (19) of said blade. 7. Tool according to claim 6. characterized in that said inner edge (162) has a radius equal to the radius of the shaft (7) of said auger and said outer edge (161) has a radius equal to the diameter   external of said helical screw (9).   8. Tool according to any one of claims 4 to 7.   characterized in that said vertical shaft (7) carries. at its end.   peaks (14), distributed around its periphery and a fixed blade (15) whose leading edge is equipped with peaks (16) which prolongs   the lower end of said helical screw.   9. Machine for performing drilling according to claim 1. characterized in that it comprises a tool according to any one Claims 4 to 8.