Method for stabilizing structures

Abstract

Stabilizing structures by means of geotechnical works involving treating the soil by injecting consolidating mixtures and / or installing posts to consolidate the foundations. The procedure involves performing real-time monitoring using acoustic emission (AE) technology capable of detecting the constraints induced by the above-mentioned geotechnical works on the structures.

Description

PROCESS FOR STABILIZING STRUCTURES

[0001] The present invention relates to a method for stabilizing structures, particularly foundations, and which provides for monitoring carried out by means of a survey and parametric analysis of the acoustic emissions generated in the material of the constituent elements of the structure during construction site operations. These are consolidation interventions by injecting cement or synthetic mixtures with expansive power into the foundation soil and / or by installing piles in the soil up to more compact soil layers and which are subsequently anchored to the existing foundation structure.

[0002] As is well known in the field of soil mechanics, an elementary volume of soil can be schematized as a porous medium consisting of soil grains (solid skeleton) and voids. The latter may be not at all, partially or totally occupied by pore water: in the first case we speak of "dry soil" (degree of saturation S = 0), in the second case of "partially saturated soil" (0 < S < 1), and when all the voids are occupied by water, of "saturated soil" (S = 1).

[0003] When said elementary volume is subjected to the application of an external load, depending on its intrinsic permeability, a state of tension is generated in its mass to which a state of deformation corresponds.

[0004] When these observations are transferred from the microscale (elementary volume) to the macroscale (natural volume), it becomes evident how a mass of natural soil - imagined as a multitude of elementary volumes - when subjected to external actions (application of loads, variations in the degree of saturation, etc.) can deform by varying its initial volume with a corresponding variation in the void ratio and / or the degree of saturation.

[0005] In the field of civil engineering, these geological-geotechnical aspects are of primary importance not only in the design, but also in the operational phase of the foundation structures of any artifact (building, pavement, etc.). In the process of transferring loads from the structure to the ground, it is necessary to ensure the balance of the soil-foundation node to which the stability of the superstructure is linked.

[0006] Any alteration of the foundation soil of an existing structure can be the potential cause of its subsidence. These subsidences can compromise the equilibrium conditions of the superstructure, leading to the appearance of deformations and cracks on structural and non-structural elements.

[0007] To restore stability conditions, it is essential to first analyze the pathology, then carry out any structural and / or geological-geotechnical diagnostics, consider the different applicable solutions among those possible, and choose and design the one deemed most appropriate.

[0008] Among the various "traditional" solutions, as used for several decades, there is undoubtedly the one that consists of transferring the loads of the structure to more compact soil layers, by means of deeper foundation piles, aligned longitudinally to the existing foundation and with a suitably defined spacing.

[0009] Downstream of the intervention, the compressible soil layers are bypassed and will have no load-bearing function.

[0010] To reduce the level of invasiveness of the intervention, especially on existing structures, the installation of small-diameter piles (also called micropiles) is becoming increasingly common. These are generally metallic and consist of several interconnected elements that are screwed or driven into the ground to the deepest support state. Once the desired load capacity is reached, or when the structure has been lifted using a laser level, operations are stopped and the head of the micropile is connected to the structure, which in this case is done by means of plates bolted to the foundation.

[0011] The (cross-sectional view of a generic foundation system during operational phases) schematizes a typical micropile installation intervention. After carrying out an excavation (A) which exposes the existing foundation (B), the process involves the following sequence of phases: Fixing the steel plate equipped with a ring (C) to the foundation by bolting (D); Installing the hydraulic jack (E) on the plate by means of a metal driving template (F) and installing the hydraulic circuit (G) connected to a generator; Inserting the pile (H) through the metal template and driving the pile in portions until the desired layer (I) is reached and / or the desired point load (J) is reached and / or the structure reacts to the uplift (K); Blocking the pile to the foundation by bolting (L), cutting off the excess pile portion (M) and backfilling the excavation (N).

[0012] These traditional repair solutions are characterized by a medium to long duration, as well as a high level of invasiveness.

[0013] Indeed, their execution requires medium to large diameter drilling operations, punctual or linear excavations which are often difficult to apply in contexts with reduced accessibility.

[0014] Faced with these limitations, processes have been increasingly used in recent decades to improve the quality of the supporting soil by injecting cement ("jet grouting") or synthetic products (polyurethane resin).

[0015] Illustrates the typical expansion diagram of a two-component polyurethane resin. Looking at the diagram it is possible to observe that once the mixing is complete (t=t0), the resulting mixture is injected into the ground through small diameter pipes, previously installed by means of a perforation made using a hand drill. The mixture, still liquid, comes out of the pipe at the desired depth and begins to impregnate the surrounding soil (impregnation phase, t0 <t<t1). Après un certain temps, qui varie en fonction de sa composition, le mélange augmente de volume (phase d'expansion - t1≤t<t2) jusqu'à ce que l'énergie générée par la réaction chimique soit épuisée (t=t2) et que le produit se polymérise, devenant stable et inerte (phase de polymérisation, t2≤t≤t3).

[0016] The high expansion power is capable of generating mechanical action on the soil (consolidation) due to the increase in grain density, filling / crushing of voids and displacement of pore water.

[0017] These mechanical effects produce an increase in the bearing capacity of the soil volumes affected by the treatment, as well as a reduction in the overall permeability of the environment with a consequent improvement in water behavior.

[0018] As illustrated in (sectional views of a generic foundation system during operational phases), for a standard intervention, all procedures involve the following phases: The making of small diameter perforations through the foundation (- A), generally positioned at a distance in plan varying between 0.50 m and 1.50 m (value which generally corresponds to the radius of action of the formulation in a cohesive and granular context); Continuation of the same perforations in the soil layers to be treated up to the desired depth (- B); Installation of a series of small diameter pipes (- C) implanted in the soil at different depths so as to have several injection points on the same vertical; Punctual treatment by cyclic injections of cement or synthetic mixtures while making appropriate pauses using an injection terminal connected to a suitably equipped injection station (- D).

[0019] During micropile implementation operations, but especially during the execution of consolidation injections, one of the technical and operational problems encountered in the state of the art concerns the monitoring and management of superstructure uplifts.

[0020] If the state of tension and deformation induced by the uplift is not compatible with the superstructure (i.e., if the threshold tensional state of resistance is exceeded), it is very likely that the intervention could damage the structure or aggravate the pathologies already present.

[0021] Very often, these pathologies develop within the material that makes up the structure without manifesting themselves in an obvious and / or appreciable way to the naked eye. In addition to the problem of controlling variations in the "state of tension-deformation" of the structure, there is also the problem linked to the difficulty of locating any structural damage after intervention that is not visible to the naked eye.

[0022] It is therefore evident that in this type of work, in addition to having appropriate instrumentation to control geotechnical operations, it is equally important to monitor the possible effects induced by the backlashes related to pile driving (in the case of micropiles) and by the thrust of the expansion of the injection mixture (in the case of mechanical improvement treatment) on the overlying structure. This is to guarantee structural safety.

[0023] The proposed monitoring allows us to

[0024] - detect the warning signs of a crack (preventive monitoring);

[0025] - define the origin and propagation of crack precursor signals (mapping).

[0026] Injection consolidation intervention history

[0027] In the known state of the art, the execution of ground consolidation works by injection involves the lifting of the aerial structures resting on the ground to be treated by means of "continuous control by laser level or other system".

[0028] With such instrumentation, when the equipment signals the beginning of lifting of the construction or the ground surface (order of magnitude linked to the degree of precision of the instrumentation used - generally 1 / 10 èmemillimeter), the treatment of the current injection point is considered complete. This lifting is associated with very strong compaction of the soil around the injection point, the values ​​of which are generally higher than the minimum required values.

[0029] With such an approach, it is obvious that we are seeking to obtain a lift in order to validate each injection point as well as a reduction in the opening of cracks (permanent or temporary) if they already existed.

[0030] However, even if site operators were to stop the injection cycle as soon as the instrumentation detects movement of the structure, this would not stop the expansion of the quantity already injected. Such an event would induce an increase in the stress-strain state, with the potential appearance of new cracks or the aggravation of existing ones. The instant at which this event occurs, as well as the quantity of resin injected, remain entirely random and linked to specific site conditions.

[0031] Thus, there are frequent situations in which site operators, although quickly stopping the treatment of an injection point at the moment in which a lifting is detected, can only note its existence and wait for it to end.

[0032] Patents EP1914350 and EP2543769 provide for geophysical monitoring of the treated soil during injection by means of acquisition and development of 3D electrical resistivity tomographies. The evaluation of the mechanical improvement is carried out by means of penetrometer tests.

[0033] Document EP1914350 provides that the soil treatment is carried out until "the electrical resistivity values ​​of the subsided zone are brought back to the non-subsided values ​​taken as a reference".

[0034] The same applicant, with the introduction of patent EP2543769, found that "it is not always possible to practically provide an adjacent volume of soil that is not subsiding and that, due to the chemical-physical and structural characteristics, can be taken as a benchmark in the process of stabilization and homogenization of the subsiding soil volume." Document EP2543769 states that the "effects induced by sequential and targeted injections of expansive mixtures into subsiding soil volumes are recognized through measurements of variation in electrical resistivity Δρ expressed as a percentage (%)" (with ρ = electrical resistivity).

[0035] Without prejudice to the usefulness and reliability of the information provided by electrical resistivity tomographies, the geophysical instrumentation used in the two patented procedures (EP1914350 and EP2543769) does not allow the effectiveness of the intervention to be verified at each injection point, nor does it allow the uplifts induced on the structure to be monitored.

[0036] Between one operation of acquiring, inverting and processing an electrical resistivity tomography and the next, there is a certain period of time (time-lapse monitoring), during which site operators have no instrumentation to carry out the correct dosage of the formulation quantities and to verify in real time their effect on the above-ground structures. This fact increases the risk of undesirable and unmanageable effects occurring when the resin has already been injected and is in the expansion phase.

[0037] The applicant, with patent application 102019000019789, has already proposed a method of consolidating soil by injecting expansive resins while carrying out acoustic monitoring with highly sensitive geophones.

[0038] This process provides information on the action of the resin injected into the ground in real time and allows site operators to manage the different injection cycles, confirm saturation of the volume of interest and act in a timely manner if abnormal and out-of-range noises are detected.

[0039] Indeed, once a generic injection cycle has been carried out, the resin in the expansion phase generates noises induced by friction with the soil as well as by the effects of friction and compaction of the grains, the filling of voids and the displacement of pore water (if present). These noises are audible at the surface through high sensitivity geophones located on the injection verticals close to the volume of soil impacted by the treatment and the injection point. Thanks to a control unit connected to the geophones, a series of acoustic parameters can be associated with the noise generated by the consolidation action, such as extension, smart indicator, frequency spectra.

[0040] This method therefore makes it possible to locate the expansion action in the environment of the measurement vertical and, in addition, to control the injection cycles with the execution of pauses between the successive cycles relating to the same injection point in which the following cycle is resumed when said acoustic detection means no longer detect noise (the end of the expansion of the formulation will correspond to that of the noise detection).

[0041] In some cases, the teachings described by 102019000019789 can reduce the risk of occurrence of untimely lifting of above-ground structures (of the artifact itself or its ancillary elements) even before they occur, thanks to the possibility of stopping the treatment when the characteristic acoustic parameters show saturation of the volume around the generic injection point.

[0042] However, it is not always possible to avoid undesirable effects on the structure by "auscultating" the soil, especially when the geological-geotechnical and structural conditions are unfavorable (saturated soils or overconsolidated stratigraphic alternations, fragile structures already damaged by previous pathologies).

[0043] In general, it should be assumed that, in the case of the application of expansive polyurethane resin in the soil, its expansion path remains very random and is strictly influenced by the site-specific confinement conditions (water content, void ratio, level of heterogeneity) as well as by the consolidation effect of the previous injection cycles.

[0044] The resin, at each injection cycle, will therefore diffuse by following the simplest path, i.e. the least confined, until the treated soil is completely saturated. From this moment on, there is a sharp increase in the risk of lifting of above-ground structures, which justifies the use of structural monitoring instruments in addition to soil monitoring instruments. Presentation of the invention

[0045] The aim of the present invention is to propose an alternative monitoring method to the laser level when carrying out injections of cement or synthetic mixture, as well as when installing piles. This is in order to guarantee the level of safety that these operations require.

[0046] The aim of the present invention is to overcome the drawbacks highlighted above by providing a method for stabilizing structures and consolidating soils which drastically reduces the risks of structural damage which can potentially occur during injections (uplifts, cracking, etc.).

[0047] A particular objective is to provide a procedure which, through continuous monitoring, makes it possible to

[0048] - increase the sensitivity level of monitoring the tension-deformation state of the structure resting on the treated soil;

[0049] - locate and map any structural cracks not visible to the naked eye.

[0050] These objectives, as well as others which will be specified later, are achieved by means of a method in accordance with claim 1 and to which reference is made for greater conciseness of the disclosure.

[0051] Advantageous embodiments of the invention are obtained in accordance with the dependent claims.

[0052] Detailed Description of Preferred Embodiments

[0053] Some preferred embodiments of the method, illustrative but not exclusive of the invention, will be better understood upon reading the description which follows with reference to the appended figures. These embodiments are generally applied to existing structures showing signs of instability, such as cracks or deformations of structural and non-structural elements (remedial interventions after disaster).

[0054] The process can also be implemented when volumes of foundation soil need to be treated in view of an increase in permanent or accidental loads on the overlying structure, such as the elevation and / or installation of heavy machinery (preventive interventions).

[0055] These are essentially cement or synthetic mixtures with monitoring of the overlying structure using acoustic emission (AE) technology.

[0056] It is a non-destructive monitoring method already known for testing structures and / or for verifying / diagnosing phenomena such as damage, micro-cracks, degradation, corrosion, etc. It is based on the detection of ultrasonic pulses emitted by the precursor signals of a fracture that are generated and propagate in the material from the first moments they begin to occur (for example due to the subsidence of the foundation soil).

[0057] Acoustic emission technology is based on the detection and conversion of acoustic emissions into voltage signals through transducers installed on the structure to be monitored. These transducers, thanks to special crystals, are capable of generating electrical signals at the slightest detected stress. Suffice it to say that modern transducers are capable of capturing mechanical stress of the order of 10 -9 mm and transform it into an electrical pulse of 10 -6 volts.

[0058] The (axonometric view of a damaged building corner) shows a generic application of AE to monitor corner cracking (A) due to foundation settlement (B). The instrumentation consists of a series of transducers (C) installed on the structure to be monitored and connected by cables (D) to a reading unit (E) that collects the readings. Software installed on a personal computer (F) processes and stores the acoustic emission signals propagating in the structure. The readings can also be viewed remotely in real time.

[0059] AE technology is implemented with central units capable of filtering the signals acquired by the transducers after setting an appropriate threshold value. Defining the latter allows excluding background "noise" related to the environmental context in which one operates and only considering AE signals that exceed the pre-established threshold value. Setting a threshold value also determines the degree of sensitivity and precision to be adjusted.

[0060] The basic acoustic parameters that characterize an AE pulse are amplitude and frequency, as well as the number of events produced.

[0061] From these values, also thanks to the statistical analysis methods of interpretation (fractal interpretation Beta_t, b-value, b-collapse), it is possible to predict at an early stage whether there is an evolution of the pathology. In fact, it is known that the evolution of structural cracks is associated with

[0062] - an increase in the number of acoustic events occurring in the unit of time;

[0063] - an increase in the amplitude of the event;

[0064] - a reduction in frequencies.

[0065] From the above, referring again to the, only high frequency signals (50 kHz - 1 MHz) are associated with the initiation of cracking (corresponding to the moment when cracks in a small part of the structure, called the "damage zone" begin to evolve, G).

[0066] The same pathology will develop if there is an increase in the number of EA signals in the same area, accompanied by a gradual decrease in frequency (1 - 10 kHz).

[0067] When there is a sudden increase in the number of low-frequency AE signals and a reduction in the number of high-frequency signals, it means that the damage is progressing and there is a potential structural failure.

[0068] To measure the intensity of an event we will refer to the number of oscillations, a parameter that is directly proportional to the amplitude. An event will be more intense the higher the number of oscillations.

[0069] There are two approaches to counting acoustic emissions: "ring counting" and "event counting":

[0070] - "Ring-Down Counting" consists of counting how many times the signal exceeds the threshold value;

[0071] - "Event counting", on the other hand, analyses a single event by taking into account all the oscillations caused by a given microcrack.

[0072] Regardless of the type of approach, the first crossing that exceeds the threshold value is the one that advances the counting.

[0073] As an example, a 30-day measurement campaign characterized by 148 EA events exceeding a given threshold value (A) is summarized. The increasing trend in the cumulative number of EA events (B) is symptomatic of an ongoing irreversible cracking phenomenon. In addition to the increasing number of events, the reduction in frequencies (C) and the increase in amplitudes (D) also confirm the progressive nature of the pathology.

[0074] The present invention proposes monitoring, by means of acoustic emission technology, of structures covering a soil subjected to consolidation with injections of cement or synthetic mixtures, including expansive resins, and / or with the installation of deep piles.

[0075] La shows an axonometric view of a corner of a damaged generic building with injection work in progress. This angle is the same as that of lamais with the addition of treating an injection point (H) by means of cyclic injection of expanding resin.

[0076] As previously indicated, during injection, once the expansion of the mixture has exhausted its soil consolidation actions (filling of voids, displacement of pore water, thickening of grains, etc.), the increased confinement conditions around the injection point are likely to exert a thrust ( I ) which could induce an uplift of the soil and / or the overlying structure, with a modification of the stress-strain state.

[0077] Before undergoing a proper lifting detectable by a conventional laser or radar instrument (i.e. greater than 1 / 10 mm), the structure goes through a phase where it begins to be stressed with microscopic movements, so minimal that they cannot be detected by a conventional laser or radar instrument (less than 1 / 10 mm).

[0078] During this phase, the "stress" induced on the structure by the expansion of the resin in the soil generates acoustic emissions that propagate in the material of the structure itself. Although this is a different physical quantity from a heave (the AE detects ultrasonic pulses, a laser or radar a length), knowing that sound pulses are propagating in the structure is tantamount to saying that the current injection cycle is about to exhaust the consolidation actions on the ground and begins to produce the first thrust effects on the overlying structure.

[0079] This information allows site operators to interrupt the current injection cycle for a given injection point, permanently or temporarily.

[0080] In fact, when there is an increase in the number of acoustic events, an increase in amplitude and a corresponding reduction in frequencies, the treatment of the current injection point would be definitively interrupted (permanent interruption), as this is a predictive condition for the evolution of damage.

[0081] On the other hand, if the acoustic parameters do not undergo changes predictive of damage progression, and in any case only when significant noise emissions are no longer recorded, treatment can be resumed by more carefully dosing the quantities of the following injection cycles (temporary interruption).

[0082] The invention in question also proposes to use the same monitoring approach with the EA for the execution of consolidation interventions by means of piles.

[0083] The (axonometric view of a corner of a damaged generic building with pile installation work in progress) shows the same collapsed corner as where two dark micropiles are being installed on two verticals.

[0084] Once the excavation (H) has been carried out and the current part of the foundation exposed, steel plates with slip rings (I) are bolted onto the foundation. Hydraulic jacks (J), powered by an electric unit (K), provide the thrust energy needed to drive the piles.

[0085] The piles are driven in portions until the desired layer is reached and / or the desired point load (L) is achieved. If the structure permits, a controlled lifting of the structure (M) can be carried out.

[0086] Once the desired layer has been reached and / or the target load value has been achieved (in accordance with current technical standards), the pile is bolted to the foundation, the excess part of the pile is cut off and the excavation is backfilled.

[0087] Even in this case, already during the driving of the pile, but above all and once deeper, more resistant layers capable of counteracting the driving force are reached, acoustic emissions linked to the "mechanical stress" transmitted by the advancement of the pile will begin to be generated in the material of the above-ground structure.

[0088] Although the thrust induced by the pile on the structure is more easily manageable than the thrust induced by the expansion of the injection mixture - since stopping the advancement of the hydraulic cylinder will correspond to the instantaneous cessation of the uplift effects - having early warning signs of potential damage makes it possible to optimize operations on site, reduce the risk of possible damage and increase the level of control of an uplift of the structure, should this be sought.

[0089] Under these conditions, site operators can record precursor signals of crossing an overconsolidated layer, intercepting a rock or approaching the compact layer, even before any actual uplift detectable by a laser level occurs.

[0090] Monitoring the parameters recorded by the transducers will guide site operations, which can be temporarily interrupted at the moment when the pile driving corresponds to an increase in the number of acoustic emissions associated with stability or a reduction in the number of acoustic events in the unit of time, as well as stability of the amplitudes and frequencies of the event.

[0091] When such an eventuality occurs prematurely, i.e. when the compact layer at known depths and / or the design peak load are still far away, pile driving operations may be resumed with increased caution and with appropriate measures to facilitate driving: use the reduced and strictly necessary thrust and advance speed value, drive two or more piles placed in close proximity. Driving operations shall only continue if noise emissions are not significant.

[0092] On the other hand, pile driving will be stopped definitively if, at the time of resumption of driving and despite the measures taken, there are indications of potential damage in progress, i.e. when there is an increase in the number of acoustic events in the unit of time, an increase in the amplitude of the event and a decrease in frequencies.

[0093] As mentioned above, EA is implemented with central units capable of filtering the signals acquired by the transducers after setting an appropriate threshold value. This setting allows excluding background "noise" related to the environmental context in which one operates and considering as significant for monitoring only those EA signals that exceed the pre-established threshold value.

[0094] In the case of the application of EA, the initial threshold value is also set according to the type of structure and the desired degree of monitoring sensitivity. Its value can then be calibrated during construction based on the response of the structure itself to the injections. In this way, by proceeding by homogeneous construction site areas in structural and geological-geotechnical terms, site operators will be able to calibrate on an observational basis the minimum quantities capable of beginning to transfer the "mechanical stress" from the soil to the structure in the case of injections, as well as the critical depths and limit thrusts in the case of piles.

[0095] A sufficient number of transducers properly installed and georeferenced to a local reference system, through appropriate modeling, also makes it possible to locate and map the source points and the distribution of all acoustic emissions induced by critical injections which may have caused damage (micro- or macro-fractures not visible to the naked eye).

[0096] Following the consolidation or stabilisation of the structure or foundations, it will therefore be possible to define in a precise and targeted manner the damaged areas which could require repair work.

[0097] The way in which a structure is damaged, and therefore how sound emissions propagate, is closely linked to its fragility (or ductility) in relation to certain stresses (compression, traction, torsion, etc.) as well as to its geometric characteristics (shape, size, complexity), its complexity and the connections existing between the elements that compose it. Therefore, the number and positioning of transducers to be installed to carry out the control with the AE - in addition to taking into account the pathology that affects the structure - must also and above all consider the type of structure and its geometry.

[0098] In structures characterized by low rigidity (such as masonry structures), any damage induced by uplift will be found mainly near the intervention area on the ground. On the other hand, in structures with greater rigidity (for example, frame structures with reinforced concrete beams and pillars), damage will not necessarily occur near the treated areas. This is because elements with greater rigidity (beams, pillars, joists, etc.) can transfer the state of tension and deformation to portions of the structure further away from the intervention area, in a rigid manner and without being damaged.

[0099] In masonry structures, it is therefore possible to limit ourselves to placing the transducers near the soil treatment areas, while in the case of frame structures it is advisable to also cover more distant areas, but structurally connected to the intervention area. This is in order to detect and locate possible microcracking phenomena induced by the transfer of the tension state by more rigid elements such as reinforced concrete beams and pillars.

Claims

A method of stabilizing structures, comprising the following phases: (a) application of one or more constraints induced by geotechnical works to achieve consolidation of the foundations; (b) Structural monitoring carried out during the aforementioned application phase a) and characterized by the use of acoustic emission (AE) technology capable of detecting acoustic emissions attributable to the constraints induced by the aforementioned geotechnical works. Method according to claim 1, wherein said monitoring step b) is capable of evaluating in real time one or more characteristic parameters of said acoustic emissions associated with the frequency and / or the amplitude and / or the number of acoustic emissions exceeding a predetermined threshold value. Method according to claim 1 or 2, wherein said characteristic parameters are chosen from the group comprising the number of acoustic events, the frequency, the amplitude, the time scaling (Beta_t), the level of damage reached (b_ value ), the collapse damage level (b_ rupture ) and similar. A method according to any preceding claim, wherein said acoustic detection means comprises transducers or similar detection devices for converting ultrasonic pulses into electrical signals using acoustic emission technology (AET) or an equivalent system. Method according to one of the preceding claims, in which said application step a) comprises a step of consolidating the soil by means of cyclic injections of a consolidating mixture, said control step b) being adapted to detect the number of acoustic emissions attributable to the stresses induced by the expansion of said mixture once it has exhausted the consolidation actions on the soil. Method according to claim 5, wherein said consolidating mixture is chosen from expansive polyurethane resins, expansive formulations, cement-based mixtures, synthetic mixtures. Method according to claim 5 or 6, wherein said step of consolidation by injection, at a given injection point, is temporarily interrupted when the injection cycle produces an increase in the number of said associated sound emissions, during a period of time corresponding to the expansion phase of the mixture, to a stability or a reduction in the number of acoustic events in the unit of time, to a stability of the amplitude of the event and to a stability of the frequencies; said injection processing being resumed when significant acoustic emissions are no longer recorded, that is to say above a predetermined threshold value. Method according to claim 6 or 7, wherein said injection consolidation step comprises the following steps:- making small diameter perforations through the foundation;- continuing the same perforations in the soil layers to be treated up to the desired depth;- installing in the perforations one or more small diameter pipes through the soil layers to be treated up to the desired depth. A method according to claim 8, wherein said step of monitoring acoustic parameters is carried out during said injection consolidation phase and during pauses between one injection cycle and the next with respect to the same injection point and wherein the definitive interruption of the treatment at each of the injection points occurs once the current injection cycle, with respect to a given injection point, highlights potential damage in progress or when, with reference to a cycle of acoustic emissions induced by the treatment, it is recorded in a period of time corresponding to the expansion phase of the mixture - an increase in the number of acoustic events in the unit of time; - an increase in the amplitude of the event; - a reduction in the frequencies. Method according to any one of claims 5 to 9, wherein said injection consolidation step can occur at one or more injection points located on the same injection vertical. Method according to one of the preceding claims, wherein said application step (a) comprises implementing piles in the ground by driving them into more compact soil layers and then anchoring them to the existing foundation structure, wherein the acoustic emissions are at least partially generated by the "mechanical stress" transmitted to the structure by the counter-thrust exerted by the piles once they have reached deeper and stronger layers which are capable of counteracting the driving or screwing force with a reaction at least equal and opposite to the loads transferred from the part of the structure located above, said step of controlling the acoustic parameters being carried out during the operations of implementing the piles in the ground. The method of claim 11, wherein the operations of driving said piles into the ground are temporarily interrupted at the instant when said operations produce an increase in the number of said acoustic emissions associated with a stability or reduction in the number of acoustic events in the unit of time, a stability of the amplitude of the event and a stability of the frequencies. Method according to claim 12, in which said operations of implementing said piles only resume if, during the continued advancement of said pile in depth, no more significant sound emission is recorded, that is to say above a predetermined threshold value. A method according to any one of claims 11 to 13, wherein the final interruption occurs once the resumption of pile driving operations in the ground has potential damage in progress, i.e. when there is:i. an increase in the number of acoustic events in the unit of time;ii. an increase in the amplitude of the event;iii. a reduction in frequencies.

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