Process for stabilizing foundations that have undergone soil settlement

Abstract

The present invention relates to a method for stabilizing the foundation of a building by micropiles (100) driven into the ground, characterized in that it comprises, after driving a hollow micropile (100) having a longitudinal channel into the ground, a step of forming a bulb (150) under the end of said micropile by means passing through said channel of said micropile (100), a step consisting of injecting a grout via said channel to fill the volume of said bulb (150), then a step consisting of engaging in said channel a mechanical connection terminated at its distal end by an anchoring means, to position said anchoring means in said bulb (150) and to fix the proximal end on the anchoring system (13) of the micropile (100) on the foundation (1). Abstract figure: figure 1

Description

Title of the invention: Method for stabilizing foundations that have undergone soil settlement Field of invention

[0001] The present invention relates to the field of jacked micropiles.

[0002] The construction of jacked micropiles is carried out using a driving device. This device allows the penetration of small diameter cylindrical tubes into the ground, generally with a diameter of less than 200 mm.

[0003] The sinking is carried out several meters deep into the ground.

[0004] Once the pile has reached the desired load-bearing capacity, the jacking stops.

[0005] The purpose of creating this type of pile is to take the loads of the building and also allows it to be raised if it is a sagging building that we want to raise by a few centimeters for example. The piles are spaced adequately and connected to the existing structure in order to take up its load which will have been transmitted to the ground.

[0006] Unlike driven piles, the jacked pile driving technique does not cause vibration or deafening solid-borne noise. They can therefore be installed both inside and outside a building in order to stabilize foundations that have suffered subsidence on unstable soils.

[0007] Jacked micropiles can be built on reinforced foundations regardless of the date of construction of the building. In the case of intervention on buildings under construction, reservations will be placed during the pouring of the concrete, then removed to allow the driving of jacked micropiles if necessary.

[0008] In the case of intervention on new buildings, the jacked micropiles are driven in before the foundations are created. On the other hand, if the intervention takes place on existing buildings, the jacked micropiles are fixed to the edges of the existing foundation soles using metal or reinforced concrete connecting blocks. The driving is carried out by autonomous hydraulic jacks that can be positioned even inside the buildings to be treated; the jacking device can also be fixed to the lateral part of the foundation of the house. In the latter case, the counter-thrust necessary for the working dynamics is guaranteed by the own weight of the structure of the building itself. It is carried out by compression.

[0009] The base of the hydraulic jack is secured to two threaded rods previously planted on either side of the hole drilled for the insertion of the jacked micropile. Blocked by mechanical action or by the use of sealing resin, the threaded rods constitute two secure anchor points to immobilize the machine during the driving phase.

[0010] This tube is fixed to the foundation by the fixing system (for example metallic) which itself is fixed to the structure to be repaired using high-strength cements or by the action of epoxy resin. State of the art

[0011] Patent application EP1985765 describes a jacked micropile system comprising a receiving unit formed of an axial cylindrical sleeve and receiving a portion of the upper external portion of a micropile and a connection unit formed of a transverse support plate rigidly connecting the receiving unit to a foundation. The receiving unit and the connection unit form a support or support frame. An assembly unit mounts an actuator, for example a jack, on the support or support frame in a removable manner.

[0012] Patent US3796055 describes another solution for carrying out the underpinning and raising of parts of the foundations of a building consisting of forming a pit along the part of the foundations to be raised, arranging a vertically elongated pipe in the pit, gripping the side of the pipe while progressively extending the hydraulic drive means against the reactive force of the weight of the part of the foundations so as to push the pipe into the ground.

[0013] This last step is repeated until the pipe has been driven to the desired depth, then a driving cushion is formed and supported by the upper end of the pipe.

[0014] US Patent 11085167B2 describes another example of a system for permanently elevating and supporting a sunken building foundation footing, comprising: • a cylindrical sleeve disposed within a hole drilled in the footing from the upper surface of a portion of the footing adjacent a wall of the rod to the lower surface of the footing, the sleeve having an inside diameter large enough to allow passage of the pier extensions; • a support positioned on the upper surface of the sole above the sleeve, the support having a central hole of a diameter equal to or greater than the inside diameter of the sleeve; and • a mechanical connection between the bracket, the sleeve and the sole plate for transmitting a lifting force from the bracket to the sole plate, the mechanical connection comprising a series of anchor bolts extending from a threaded upper end downwardly through the bracket and the sleeve to an L-shaped lower end configured to bear on the lower surface of the sole plate when the nuts of the upper ends of the anchor bolts are tightened against the support.

[0015] US patent application 2005 / 220544 describes a method in which piles are driven into the ground by hydraulic mechanisms until the pile reaches the bedrock or until the resistance of the pile is equal to the compressive weight of the structure. Once these piles are fixed in a stable underground stratum or in several stable underground strata, further lifting by the hydraulic jacks increases the level of the foundation.

[0016] When the foundation is raised to the desired level, the piles are permanently fixed to the foundation. The hydraulic jacks are then removed.

[0017] Patent EP0317458B1 describes a method for implementing a foundation by creating a mass made up of the ground itself according to which: • at least one deep anchor point is created, connected to an anchor line extending towards the ground surface and extending beyond this surface, • a slab is placed on the surface with at least one opening for the passage of said anchor line, • and traction is exerted on the slab in the direction of the anchoring point by tensioning the anchoring line by means bearing on said slab, characterized in that: • an anchoring means is driven into the ground by driving along the anchoring line capable of pivoting from a substantially vertical driving position to a position substantially parallel to the ground, • said anchoring means is pivoted by exerting traction on the slab, so as to obtain an underground ground stop effect provided by said anchoring means, and this traction is continued to prestress the ground until the service force necessary to maintain the structure to be carried out on the surface is obtained. Disadvantages of the prior art

[0018] The bearing capacities of prior art micropiles depend essentially on the anchoring depth and the grout injection pressure. The bearing capacity of the pile is the sum of the lateral friction of the pile in the ground and the tip term.

[0019] However, the peak term taken into consideration in the calculation of micropiles both in compression and in tension is quite low due to the reduced diameter of the micropile. Solution provided by the invention

[0020] The invention relates in particular to a method for stabilizing the foundation of a building by micropiles driven into the ground, characterized in that it comprises, after driving into the ground a hollow micropile having a longitudinal channel, • a step of forming a bulb under the end of said micropile by means passing through said channel of said micropile, • a step consisting of injecting a grout via said channel to fill the volume of said bulb, • then a step consisting of engaging in said channel a mechanical connection terminated at its distal end by an anchoring means, to position said anchoring means in said bulb and to fix the proximal end on the anchoring system of the micropile on the foundation.

[0021] Advantageously, said distal end of said mechanical connecting means is secured to a harpoon.

[0022] According to a first variant, said mechanical connection means consists of a metal rod. According to a second variant, said mechanical connection means consists of a metal cable.

[0023] Preferably, said step of forming a bulb consists of injecting a fluid through the channel of the micropile under a pressure greater than 20 bars, then injecting a grout through said channel to fill the bulb.

[0024] Detailed description of a non-limiting example of embodiment

[0025] The present invention will be better understood on reading the following description, concerning a non-limiting example of embodiment illustrated by the appended drawings where:

[0026] [Fig-1] [Fig.l] represents a schematic view of a foundation stabilized by a micropile according to the invention. General principle of the invention

[0027] The general principle of the invention consists of driving micropiles into the ground, in particular by jacking, according to the usual methods in the field of foundation stabilization.

[0028] The invention aims to increase the load-bearing capacity of micropiles in compression and traction by: • The creation of a bulb at the end of the micropile • the creation of an additional inextensible connection between the bulb formed under the distal end of each micropile, after the micropile has been driven into the ground, and • the system for fixing the micropile to the building structure. Process Detail

[0029] A drilling tool consisting of a hollow metal bar is inserted into the jacked hollow tube. This bar makes it possible to reach the end of the jacked micropile.

[0030] The drilling tool deconstructs the ground beyond the head of the jacked tube by injecting, via the rotary drilling tool, a jet of water and air under a pressure of 20 bars at 100 bars. The soil that penetrated the tube when it was driven into the ground is also forced upwards.

[0031] This space thus created under the micropile typically has more than 3 to 5 times the section of the micropile, and a height similar to its section. Once the volume of the bulb cavity has been created, a cement grout will be injected under pressure which will penetrate and consolidate the entire volume of the cavity thus created.

[0032] The drilling cutting tool is then removed for reuse.

[0033] Then, before the grout sets, a rod or cable is introduced through the micropile channel, terminated at its distal end by an anchoring means, typically a harpoon which can be folded to present a transverse size smaller than the section of the micropile channel, then deployed, at the exit of the micropile, to ensure anchoring in the grout present in the cavity created before it has set.

[0034] The work is then completed by fixing the distal end of the micropile to the foundation with a connection system known in the prior art, and the proximal end of the rod or cable is also secured to the foundation, for example by means of the same connection system known and adapted to allow the cable or rod to be secured.

[0035] Then the entire micropile tube will be filled with grout. The anchoring device is thus sealed in the bulb and along the micropile. Description of Figure 1

[0036] [Fig.l] represents a schematic view of the stabilized foundation after implementation of the method according to the invention.

[0037] The foundation (1) is secured to a fixing plate (13) fixed by chemical anchors (12) in a manner known in the prior art. A matting mortar is injected between the foundation (1) and the plate (13). The micropile (100) consists of an oil tube with a section between 50 and 100 mm, typically 888.9 mm, with a wall with a thickness of 5.5 mm. It has a central channel with a section greater than 50 mm.

[0038] The step of injecting water and compressed air then a grout makes it possible to form a solid bulb (150) under the distal end of the micropile (100), with a section greater than 100 mm, typically between 200 and 500 mm, and of a similar height, typically between 100 and 500 mm.

[0039] A harpoon (130) ensures the anchoring of a cable (120) or an inextensible rod; the proximal end of this rod or this cable (120) is secured to the plate (13). Instrumented variant

[0040] Optionally, a strain gauge or position sensor provides a mo- monitoring of the anchor rod or cable. It is connected to a communication circuit, typically Bluetooth or Wifi, to periodically transmit information to a server, in order to allow monitoring of the forces undergone by the foundation and micro-displacements of the ground in order to consider additional jacking if necessary.

Claims

Claims

1. - Method for stabilizing the foundation of a building by micropiles (100) driven into the ground characterized in that it comprises, after driving a hollow micropile (100) having a longitudinal channel into the ground, • A step of forming a bulb (150) under the end of said micropile by means passing through said channel of said micropile (100), • A step of injecting a grout via said channel to fill the volume of said bulb (150), • Then a step of engaging in said channel a mechanical connection (120) terminated at its distal end by an anchoring means (130), to position said anchoring means in said bulb (150) and to fix a proximal end of the mechanical connection (120) on an anchoring system (13) of the micropile (100) on the foundation (1).

2. - Method for stabilizing the foundation according to claim 1 characterized in that said distal end of the mechanical connection (120) is secured to a harpoon (130).

3. - Method for stabilizing the foundation according to claim 1 characterized in that the mechanical connection (120) is constituted by a metal rod.

4. - Method for stabilizing the foundation according to claim 1 characterized in that the mechanical connection (120) is constituted by a metal cable.

5. - Method for stabilizing the foundation according to claim 1 characterized in that said step of forming a bulb (150) consists of injecting through the channel of the micropile a fluid under a pressure greater than 20 bars, then injecting through said channel a grout to fill the bulb (150).

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