Method for installing recoverable (MICRO)-piles

Abstract

The present invention discloses a method -MICROREC- for installing recoverable piles or micropiles, devised to provide temporary containment, stabilisation of unstable ground or provisional structural support during the construction of walls or other retaining-and-support systems executed by sequential excavation in alternate pits ("batache" technique), or to allow the continuation of further excavation works. Unlike conventional techniques, the mwethod permits the recovery of the structural elements employed as piles or micropiles and, where applicable, of the casings, thereby markedly reducing execution costs and time while minimising environmental impact. The invention likewise affords the flexibility to use different materials, dimensions and spacings in accordance with the specific requirements of each project.

Description

METHOD FOR INSTALLING RECOVERABLE (MICRO)-PILES

[0001] The present invention relates to a method for installing piles or micropiles in such a manner as to allow the recovery of the structural elements used as said piles or micropiles.

[0002] This method -together with the appropriate selection of structural materials and the corresponding dimensions and spacings, all in accordance with the specific requirements of the project at hand- may be applied to any construction work that requires a procedure capable of providing structural support, particularly in situations where traditional foundation techniques are either unviable or insufficient (for example: construction on sites with complex geotechnical conditions, such as soils containing layers of hard rock interspersed with soft soils; projects in space-constrained areas, such as densely populated urban zones; slope or embankment stabilisation; or works carried out in the vicinity of sensitive infrastructure).

[0003] Accordingly, the invention is situated within the field of construction technology, understood as the body of knowledge, methods, techniques and processes employed in the erection of buildings and civil-engineering works.

[0004] In the construction sector -whether in building works or civil-engineering projects- it is common to require the temporary stabilisation and retention of unstable ground so as to permit excavations and the erection of structures. Traditional stabilisation and retention methods rely on the use of permanent piles and micropiles.

[0005] A pile is an elongated, cylindrical structural element employed in deep foundations to transfer structural loads through layers of unstable or low-bearing-capacity soil until they reach deeper, firmer or rock strata.

[0006] A pile or micropile -the principal distinction being that piles have a larger diameter than micropiles- is ordinarily constructed by drilling a borehole which is subsequently filled with cement grout and reinforced with steel. Consequently, traditional piles and micropiles remain permanently in the ground once installed. This permanence is not only costly but may also prove problematic if, for example, the elements extend beyond the boundary of the plot under construction—i.e. into neighbouring parcels—thereby potentially interfering with future building projects on those adjoining plots.

[0007] Permanent systems generate significant costs and material waste once the temporary need for stabilisation has concluded. The inability to recover the structural elements used in traditional methods heightens the environmental impact, as additional high-impact materials such as grouts must be consumed solely for provisional containment.

[0008] Various prior patents and technologies describe the use of (micro)piles for soil stabilisation and retention; however, none of these solutions contemplates recovery of the structural elements employed.

[0009] In broad terms, the existing patents invariably describe permanent (micro)piles for instance, procedures aimed at improving load-bearing capacity through injection and reinforcement techniques that do not provide for the retrieval of the structural members; methods that emphasise vibration minimisation during installation yet likewise preclude recovery of components; or approaches that address unrelated engineering problems using solutions lacking functional similarity to the present invention.

[0010] In view of the methods customarily employed for excavation support, the present invention is characterised by:Sequential excavation in alternate pits (“batache” technique), rather than the prior requirement to create a continuous retaining wall before digging.Use of temporary, recoverable piles or micropiles, which are dry-extracted once their provisional earth-retention role is complete (their purpose is not to carry building loads), thereby preventing permanent elements from remaining in the ground.Absence of setting / curing materials, eliminating idle periods, enabling rapid mobilisation of the works and simplifying site logistics.Recovery and reuse of the steel sections, with the consequent reduction in waste, cost and carbon footprint. In other solutions the piles are not reused within the same project in successive phases (they are merely dismantled after use). In MICROREC, by contrast, sequential reuse is intrinsic to the construction method (the same piles move from one pit to the next).Employment of light machinery and no large auxiliary structures (such as heavy welded struts or hydraulic jacks) thanks to the phased construction process itself, which facilitates operation in confined urban settings.Minimisation of vibrations and impact on adjacent buildings due to phased sequencing and the progressive extraction of the retaining elements.Simplicity and speed in confined environments, as no long threaded components are required.Universality, since the method is applicable to any ground on which the construction is to be founded, whereas other solutions depend on specific soil conditions.

[0011] The present invention is distinguished from the foregoing technologies by providing a method for installing recoverable piles / micropiles that permits the structural sections to be reused while minimising environmental impact, execution time and long-term costs.

[0012] The present invention discloses a method -MICROREC- for installing recoverable piles or micropiles, devised to provide temporary containment, stabilisation of unstable ground or provisional structural support during the construction of walls or other retaining-and-support systems executed by sequential excavation in alternate pits (“batache” technique), or to allow the continuation of further excavation works.

[0013] Unlike conventional techniques, the method permits the recovery of the structural elements employed as piles or micropiles and, where applicable, of the casings, thereby markedly reducing execution costs and time while minimising environmental impact. The invention likewise affords the flexibility to use different materials, dimensions and spacings in accordance with the specific requirements of each project.

[0014] The invention addresses the technical challenge of providing reliable temporary arth-retention and stabilisation in deep excavations or confined urban sites where conventional piling methods require permanent concrete or grout-filled piles. Such traditional systems entail high material and disposal costs, generate environmental waste, impose curing delays, and may trespass beyond the site boundary, thereby constraining future foundations on adjoining plots. The problem, therefore, is to devise a construction method that can furnish the necessary lateral support during excavation while allowing the structural elements to be dry-extracted and reused, so that no permanent components remain in the ground, execution time is shortened, and overall environmental impact and lifecycle cost are markedly reduced.

[0015] The present invention establishes a method for installing recoverable piles or micropiles, devised to provide temporary containment and stabilisation of unstable ground during the construction of walls or other retaining and supporting systems, or to permit the continuation of further excavation works. Unlike the traditional methods described above, this method allows the structural elements used as piles or micropiles -specifically, steel sections or other materials- to be recovered and reused on‐site by means of sequential excavation in alternate pits (“batache” technique). This markedly reduces execution costs and time while also minimising environmental impact. The invention likewise contemplates the flexibility to employ different materials, dimensions and spacings in accordance with the specific requirements of each project.

[0016] The recoverable (micro)pile method comprises the following key components:Initial drilling: A borehole is drilled in the ground with a pile- or micropile-drilling rig, e.g., a rotary-percussive rig. Depth and diameter are set by the project-specific engineering calculations for each site, and the elements are classified as micropiles or piles depending on whether the structural member has the smaller or larger diameter. Those same calculations establish the socket length that the (micro)pile must obtain beneath the final excavation level.Casing: A PVC casing -or another suitable material such as other polymers or glass-fibre- is inserted into the borehole. The casing acts as a temporary liner, stabilising the hole and facilitating both insertion and subsequent recovery of the (micro)pile.Structural-material section (constituting the pile or micropile): A cylindrical section of structural material, preferably a rolled-steel tube of slightly smaller diameter than the bore, is introduced inside the casing. This section bears the ground loads during the temporary stabilisation phase. Its wall thickness, length and diameter are determined by the project calculations. Alternatively, it may be made of aluminium, glass-fibre, carbon-fibre, polymer composites or timber, depending on strength requirements, availability and cost. A bar or lifting ring is welded inside the top end to allow hoisting for placement and removal.Tie beam: The piles or micropiles are connected at their heads by a tie beam formed from one or more rolled sections. The beam distributes loads between the (micro)piles and adds stability. At the crown, the tie beam links the (micro)piles in the excavation zone to those installed in the immediately adjacent, unexcavated zones, thus bracing the system. Connection is by offset clips made from rolled-steel flats and threaded rods, which compensate for any misalignment caused by drilling tolerances and ensure uniform load transfer.Anchored solutions: Where excavation height is considerable and design calculations so recommend, tensioned metallic anchors may be installed, giving the method the same flexibility as conventional (micro)pile systems. Anchors are installed progressively as the excavation advances and are tied back with rolled-section beams that can later be dismantled.Recovery of the structural-material section: After the concrete wall has been completed, the ground stabilised, or the temporary need otherwise satisfied, the structural sections are recovered for reuse in the same or future projects, and the bore is back-filled with a granular material such as sand or jabre. If the PVC casing cannot be extracted, it is left in place and likewise filled with granular material. Recovery proceeds in reverse order: offset clips are slackened to free the (micro)piles, the tie beam is shifted linearly to the next pit (“batache”), and a tower crane, mobile crane or truck-mounted crane hoists the section via the welded bar, separating it from the casing. In the same crane movement the recovered section can be set into the next pit, whose bore and casing will already be prepared, allowing the process to continue briskly.

[0017] Sections extracted from the first pit are used directly in subsequent ones, always leaving some (micro)piles anchored in unexcavated ground—or in ground already provided with the wall—so that the tie beam remains braced on both sides of the excavation. For uninterrupted daily progress there must always be enough (micro)piles for the pit to be excavated plus half the number required for the immediately neighbouring pits.

[0018] In conclusion, the MICROREC method offers the following advantages over traditional methods:Cost and time reduction: Because the structural sections are recovered and reused, material costs and execution time are markedly lower; as a dry technique, the system requires no curing time before load transfer.Sustainability: Recovery of structural elements minimises waste and environmental impact, fostering more sustainable construction practices.Versatility and flexibility: Applicable to a wide variety of building and civil-engineering excavation projects.Minimal impact on adjoining land: Particularly useful where temporary retention from neighbouring plots is advantageous, as the method leaves no permanent works that could constrain future developments, saving space and reducing costs and schedule.Material adaptability: The invention is not limited to a single material; structural components may be made from glass-fibre, carbon-fibre, timber, or others, according to project requirements, cost and availability.

[0019] To supplement the foregoing description and to facilitate a clearer understanding of the invention’s features, there is appended hereto, as an integral part of this specification and purely by way of illustration without limitation, a set of drawings in which:

[0020] -Schematic side view of the initial drilling, the insertion of the casing and of the Structural-Material Section.

[0021] Legend for:

[0022] “A” Common pile- or micropile-drilling rig, such as a rotary-percussive rig.

[0023] -Schematic front view of the initial drilling, the insertion of the casing and of the Structural-Material Section.

[0024] Legend for:

[0025] “A” Common pile- or micropile-drilling rig, such as a rotary-percussive rig.

[0026] “Ht” Total depth of the pile or micropile.

[0027] “b” Spacing between piles or micropiles.

[0028] -Schematic side sectional view of the system prior to commencement of excavation, showing by broken line, by way of example, the possible position of a concrete wall executed by sequential excavation in alternate pits (“batache” technique).

[0029] Legend for:

[0030] “H” Depth of the (micro)pile in the zone to be excavated.

[0031] “He” Embedment depth of the (micro)pile beneath the final foundation level.

[0032] -Schematic front sectional view of the installed (micro)pile wall.

[0033] Legend for:

[0034] “Ht” Total depth of the pile or micropile.

[0035] “b” Spacing between piles or micropiles.

[0036] “B1”: first pit

[0037] “B2”: subsequent pit in which the piles or micropiles employed in the first pit are reused.

[0038] -Schematic front view detailing installation of the Tie Beam.

[0039] Legend for:

[0040] “1” Natural ground.

[0041] “2” Back-fill sand.

[0042] “3” Casing.

[0043] “4” Structural-Material Section.

[0044] “5” Tie Beam.

[0045] “6” Retaining plate.

[0046] “b” Spacing between piles or micropiles.

[0047] -Schematic side view detailing installation of the Tie Beam.

[0048] Legend for:

[0049] “1” Natural ground.

[0050] “2” Back-fill sand.

[0051] “3” Casing.

[0052] “4” Structural-Material Section.

[0053] “5” Tie Beam.

[0054] “6” Retaining flat or plate.

[0055] - Schematic side view detailing the excavation works.

[0056] Legend for:

[0057] “H” Depth of the (micro)pile in the excavated zone.

[0058] “He” Embedment depth of the (micro)pile beneath the final foundation level.

[0059] “C” Excavator.

[0060] -Schematic plan view detailing the excavation works.

[0061] Legend for:

[0062] “b” Spacing between piles or micropiles.

[0063] “D” Unexcavated natural ground.

[0064] “E” Excavated natural ground.

[0065] “F” Concrete surface of the first pit.

[0066] “B1”: first pit

[0067] “B2”: subsequent pit in which the piles or micropiles employed in the first pit are reused.

[0068] In addition, photographs illustrating the principal stages of the installation process are provided to assist correlation with the foregoing drawings:

[0069] Figures 9 and 10 - Photographs of the initial drilling and insertion of the casing.

[0070] -Photograph of casing insertion; in this case the casing corresponds to the hollow cylinder visible in each ground bore.

[0071] Figures 12 and 13 - Photographs of the insertion of the Structural-Material Section into the casing (blue PVC hollow cylinder). The Structural-Material Section is the dark-grey rolled-steel hollow cylinder inserted into each casing.

[0072] Figures 14 and 15 - Photographs of the placement of the Tie Beam (maroon beam connecting the various dark-grey hollow Structural-Material Sections).

[0073] Figures 16 and 17 - Photographs showing excavation of the pit (“batache”) ground and construction of the concrete wall foundation, the method functioning as the definitive earth-retention system for this purpose.

[0074] The MICROREC method can be implemented optimally as described below, setting out the steps, methods and materials employed to achieve the aim of the invention, namely a method for installing recoverable piles or micropiles.

[0075] 1º) Drilling

[0076] The method commences with drilling (,,and). After setting out the site, a borehole is drilled with a pile- / micropile-drilling rig (A,; Figures 9 and 10) to the depth (Ht,) and diameter specified by the design calculations, normally leaving a portion socketed below the final foundation level (He,).

[0077] 2º) Insertion of the Casing

[0078] A PVC casing (3,and;) is then placed in the bore to prevent wall collapse and to facilitate both insertion and subsequent recovery of the (micro)pile.

[0079] 3º) Insertion of the Structural-Material Section

[0080] Once the casing is in place, the Structural-Material Sections (4,and;and) are inserted. A tubular section -commonly a rolled-steel tuve- is introduced inside the casing. These sections act as the principal (micro)piles and are dimensioned in accordance with the structural calculations. Materials and characteristics (profile type, dimensions, material e.g., rolled steel) vary with ground conditions and project requirements. A lifting bar or ring is welded to the inside of the top end to permit hoisting.

[0081] 4º) Placement of the Tie Beam

[0082] After the (micro)piles -i.e. the Structural-Material Sections- have been set (4,and;and), a Tie Beam (5,and;and) is placed transversely across them. The beam may be single or built-up, according to design requirements, and is fixed to the (micro)piles by adjustable offset clips that compensate for alignment tolerances and ensure uniform load take-up.

[0083] 5º) Execution of the Works Requiring Support

[0084] With all elements correctly installed, the works requiring ground support may proceed. Taking the example of a concrete wall erected by sequential excavation in alternate pits (“batache” technique), the pits ground is excavated (Figures 7, 8, 9 and) and the concrete wall is built conventionally (), the recoverable (micro)piles providing temporary earth retention.

[0085] 6º) Recovery of the Structural-Material Sections and Continuation

[0086] When the support or retention task is complete, the Structural-Material Sections (4, Figures 5 and 6; Figures 12 and 13) are removed for reuse in subsequent pits. The offset clips are slackened, freeing the (micro)piles in the completed areas; a tower-, mobile- or truck-mounted crane lifts each section via its welded bar and sets it in its designated position in the next pit (“batache”), ensuring uninterrupted progress.

[0087] On completion of all works, every metallic element, including the Structural-Material Sections, is withdrawn. If the casing (3, Figures 5 and 6;) can be removed without impairing ground stability, it is extracted and the bore is back-filled with granular material. If removal is impracticable, the casing is left in place and likewise filled with granular material to stabilise the bore.

[0088] The MICROREC recoverable (micro)pile method has broad and varied applications within the construction industry, including:Sequential excavation in building and civil-engineering works: Provides temporary stabilisation and containment for deep excavations or retaining walls executed by the pit “batache” method.Temporary protections on neighbouring land: Enables foundations and temporary protections to be formed on adjacent plots without permanent impact, thereby avoiding loss of space within the principal plot.Shoring and strutting systems executed by pits (“bataches”): Serves diverse shoring requirements where temporary ground support is necessary, enhancing safety on sites with complex geotechnical conditions.Temporary slope containment: Affords interim stabilisation of slopes during the construction and excavation of roads and other civil-engineering structures executed by pits (“bataches”).

[0089] The invention is readily susceptible of industrial application throughout the construction sector, both in building and civil-engineering works. Its sequence of standard operations—rotary-percussive drilling, insertion of low-cost PVC casings, positioning and dry extraction of reusable Structural-Material Sections, and assembly with adjustable tie beams and offset clips—employs equipment (drill rigs, cranes, hydraulic winches) and materials (rolled-steel tubes, polymer casings, granular back-fill) that are already widely available on construction sites. Because the same sections can be cycled from one pit to the next, contractors can span large retaining walls with a limited stock of components, drastically reducing procurement, transport, curing delays and waste disposal. The method’s adaptability to various diameters, section types and anchoring layouts—together with its compatibility with tensioned ground anchors—means it can be deployed in diverse ground conditions, from dense urban basements to infrastructure cut-and-cover works and slope stabilisation. As a result, MICROREC offers an immediately deployable, cost-efficient and environmentally sustainable solution that integrates seamlessly into current industrial construction practices and regulations.

Claims

1.A construction method by sequential excavation in alternate pits (“batache” technique) for the temporary containment, support and / or stabilisation of unstable ground, characterised in that it comprises the following sequential operations:Drilling an initial borehole in the ground at the position corresponding to a first pit (B₁);inserting into the borehole a casing formed by a PVC tube of suitable cross-section, having a diameter smaller than that of the borehole, so as to facilitate the insertion and recovery of the Structural-Material Section by reducing friction during its extraction;inserting into the casing a tubular Structural-Material Section whose diameter is smaller than that of the casing and which bears the ground loads during the temporary stabilisation and containment pase. Prior to use, a bar or lifting ring is welded to the interior of the upper end of said Structural-Material Section, enabling it to be hoisted both for positioning and for later extraction, as explained in greater detail below.interconnecting the various Structural-Material Sections by means of an adjustable Tie Beam fitted by offset clips, thereby accommodating any positional differences between the (micro)piles;providing anchors when the excavation height is substantial;dry-extracting the Structural-Material Sections, by hoisting, once the purpose of the method has been achieved [to form, in said section, a permanent retaining wall by casting a structural cementitious material] so that, once hoisted, the same Structural-Material Section is set in the adjacent pit (B₂), the foregoing stages being repeated successively until the retaining wall has been completed, after which the Structural-Material Sections are finally hoisted and removed (never remaining in the ground) for use in other projects;recovering the casing if it has been used and can be withdrawn without compromising ground stability, or otherwise leaving the casing in situ; andback-filling the borehole (or the casing, where it remains in situ) with a granular material.2.The method according to claim 1, characterised in that the Structural-Material Sections acting as piles or micropiles may be of rolled steel, aluminium, glass fibre, carbon fibre, polymer composites, timber or other construction materials that permit their extraction from the borehole.3.The method according to claim 1, characterised in that the initial drilling of the ground is carried out with a conventional pile- or micropile-drilling rig, such as a rotary-percussive rig, or any other suitable existing rig.4.The method according to claim 1, characterised in that the Structural-Material Sections are inserted by hoisting them with a tower crane or mobile crane and positioning them in the required location.5.The method according to claim 1, characterised in that the dry extraction of the Structural-Material Sections is effected by slackening the offset clips to release the (micro)piles from the completed zones and then hoisting them with a tower crane or mobile crane, and positioning them in their corresponding locations in the next pits so as to ensure continuous progress of the works.6.The method according to claim 1, characterised in that the casing is recovered by means of a tower crane or mobile crane and / or hydraulic equipment or systems.7.The method according to claim 1, characterised in that the granular material used to back-fill the borehole (or the casing where the latter cannot be withdrawn and remains in situ) is sand, jabre, gravel or any other construction material capable of stabilising the ground.8.The method according to claim 1, characterised in that tensioned anchors may be included when the excavation height is substantial and the technical design so recommends, said anchors being installed progressively as the excavation advances and being connected by rolled-section beams that allow their tensioning, load transfer and subsequent dismantling.

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