RU2403341C1 - Method for manufacturing of foundation from boring piles - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: in method of pile footing manufacturing from boring piles in soils containing sporadically arranged zones of loose sands or easily compacted soils, including production of well in soil, supply of fluid hardening material in it, preferably plastic concrete mix, formation of pile shaft by pulse actions - for driving of boring piles in pile field or in a separate cluster made of boring piles, first exploratory pile of maximum length is produced, determined by data of geological engineering survey with account of maximum depth of foot occurrence of loose sands or foot of others, easily compacted soils in nearest points of soils investigation. After filling of well with fluid hardening material, trial actions are executed in discretely arranged points along well depth by single pressure pulses. Source of pulses is moved along depth of well after each action, and by change of hardening material flow after each pulse, lower border of deepest zone is determined, in which soul is compacted abnormally easily. Then produced data is compared to data of engineering survey, pile footing is formed from pile, and length of piles arranged between specified exploratory piles is adjusted by results of trial compaction of soil in exploratory piles.

EFFECT: reduced labour intensiveness, consumption of materials and energy without reduction of bearing capacity of pile footing as a result of maximum possible application of strength properties of complex soil foundation, including sporadically represented zones of loose sands.

11 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of geotechnical construction, namely, to the manufacture of bored and bored injection piles in complex soils containing sporadically represented abnormally weak or friable, easily compacting zones, for example, in the presence of friable sands at the base with an unpredictably changing shape of their sole. The invention can also be applied in the establishment and elimination of zones of abnormally decompressed soils during their deep compaction.

Building norms and rules (SNiP) and the Code of rules (SP) allow the lower ends of driven piles to rest on loose sands, but at the same time they need to determine the bearing capacity according to the results of static tests of these piles [SNiP 2.02.03-85 (clause 4.3) and SP 50-102-2003 (Clause 7.2.3)]. In this case, the efficiency of using driven piles is reduced to zero, since the cost of conducting a static test of one pile is several times higher than the cost of the pile itself with its immersion. In addition, the aforementioned standards [SNiP 2.02.03-85 (clause 4.11) and SP 50-102-2003 (clause 7.2.13)] require taking into account the forces of negative (negative) friction of the soil on the side surface of the piles arising from the settlement of near-pile soil, which did not complete the consolidation process. The building norms and rules do not stipulate assumptions and conditions for the possibility of supporting the lower ends of the drill piles on loose sands, which implies that the drill piles must cut through the entire thickness of loose sand. In difficult soil conditions, when designing, they always envisage deepening of drilling piles in the thickness of soils lying below the sole of loose sand. The depth of the roof of the soil underlying the loose sands is determined according to engineering and geological surveys. Standards [SP 50-102-2003, Appendix B] require exploration wells to be surveyed for soils for buildings and structures of 1 (high) responsibility level on a 20 × 20 m grid, and sounding points on a 10 × 10 m grid. For less critical buildings the grid of exploration points for the study of base soils is even larger. With such a rare location of exploration wells, bedding between exploration wells can vary significantly. When designing a pile foundation, take the depth of loose sand or other easily compressible soils at the base according to the maximum depth established at the exploration points of the study around the considered section of the pile field. The distance in the light between the trunks of drill piles, established by the standards, should not be less than 1 meter [SNiP 2.02.03-85 (clause 7.9) and SP 50-102-2003 (clause 8.13)]. Thus, dozens of piles can be placed between the nearest exploration wells, the depth of which is taken as a margin of safety with a clear excess, due to ignorance of the real lower boundary of the occurrence of loose sand or other easily compressible soils.

A known method of manufacturing a bored pile in the ground, including the formation of a well, the installation of a reinforcing cage and filling the well with concrete mixture. In this case, the well sinking and installation of the reinforcing cage is carried out simultaneously, using an electro-hydraulic device, the discharge head of which is located on the lower end of the reinforcing cage. The concrete mixture is laid simultaneously with the deepening of the electro-hydraulic device and the reinforcing cage (SU No. 906194, E02D 5/34, E02D 11/00, published 07.12.92, bulletin No. 45).

However, the rate of penetration of the well by an electro-hydraulic device is small, so the complexity of the method is very high. It is very difficult to guarantee proper quality, in particular to provide the required value of the protective layer of concrete. When a well is formed with simultaneous immersion of the reinforcing cage and filling of the formed well with concrete mixture, parts of under-loaded reinforcing cages always differ in length, since in the case of sporadic occurrence of loose sand or other easily compressible soils, the formation of the well (and therefore piles) will end at different depths levels.

The objective of the present invention is to reduce the complexity, consumption of materials and energy to create a pile foundation without reducing the bearing capacity of the latter due to the maximum possible use of the strength properties of a complex soil base, including sporadically represented zones of loose sand or other easily compressible soils, especially if the lower boundary of their occurrence in the limits of the construction site changes dramatically from one exploration point of soil research to another.

To solve this problem, the known method of manufacturing a pile foundation from drilling piles, including the formation of a well in the soil, the supply of a flowing hardening material into it, the formation of a pile shaft with discrete pulsed force and reinforcing a pile (if necessary), is supplemented by the following operations.

Before mass production of piles begins, in each pile bush, at least one exploratory pile is first made. The location of prospecting piles in the bush is determined at points that are mostly farthest from the center of each pile of piles in the direction of the points of engineering and geological surveys of foundation soils closest to each bush, in which zones of loose sand or other easily compressible soils were discovered (hereinafter - zones of easily compacted soils) , amenable to compaction when exposed to them by force pulses. The length of these prospecting piles, i.e. the depth of the wells for these piles is taken according to engineering and geological surveys at the nearest points. At the same time, the length of each prospecting pile should, of course, ensure its guaranteed deepening in dense soils, underlying the most deep-seated, easily compacted soils found at the points of engineering and geological studies of the base soils closest to the pile under consideration. An exploratory well is filled with a flowing (plastic) hardening material, mainly cement mortar or concrete mix with mobility P-4 ... P-5, while previously, either simultaneously or after filling the well with flowing hardening material, the equipment is immersed into the well with which discrete dynamic disturbances at local points recorded along the depth of the well. As a source of such impulse perturbations, a well-known explosion generator or electrode system can be used, where a high-voltage electric discharge (electric breakdown in a moving concrete mixture) occurs between the electrodes in a moving concrete mixture representing pseudo-liquid. Other sources that create discrete pressure pulses can also be used. Simultaneously with immersion in the well of a source of dynamic impulse impacts, starting from a depth close to the sole of the highest lying lower layer of the zone of easily compacted soils, the level of which is established at the points of engineering and geological studies of the soil of the base closest to the exploratory pile, they carry out discrete impulse impact effects. After each pulse, the source of dynamic effects is immersed in the well for a certain step (the distance between the individual points of impact along the depth of the well), which is set based on the required accuracy of determining the lower boundary of the occurrence of soft soils, i.e. occurrence of their sole (roofing of dense soils). The optimum distance along the length of the prospecting pile between the points of creation of the impulse disturbances should not exceed two diameters of the working pile. The high pressure created at the moment of the pulse acts on the flowing hardening material with which the well is filled and which transfers the energy of the pulse action to the surrounding soil, with certain energy losses due to dispersion and a decrease in specific energy due to its distribution in an increasing volume as the distance from the disturbance source . In the local zone around the source of perturbation, due to the dynamic action, the soil is compacted, and fluid hardening material instantly fills the volume freed up by compaction of the soil. At the wellhead, a sharp decrease in the level of hardening material, in particular plastic concrete mix, is clearly observed. If the pulse action in the well occurs at the place where the layer of the easily compacted soil zone was discovered, then at the wellhead there will be a failure of the concrete mix. Failure should be considered a decrease in the level of flowing hardening material, 5 times or more exceeding a decrease in the level of hardening material during pulsed actions outside the zone of easily compacted soils. Throughout the area of easily compacted soils, failure precipitation of fluid hardening material at the wellhead will be observed as a reaction to soil compaction during dynamic impulse actions in this zone. Submerging a source of impulse disturbances, while creating dynamic impulses, up to the bottom of the well, the lower boundary of the most deeply lying zone of easily compacted soils is established. The present invention is aimed at establishing the lower boundary of the deepest zone of easily compacted soils by fixing the flow rate of hardening fluid after each pulse. If the prospecting pile is subsequently used as a working pile, then after determining the sole of the deepest lying zone of easily compacted soils, the prospecting pile is completed to the state of the design working pile. To do this, compact the soil under the lower end of the pile in accordance with the requirements of SNiP 3.02.01-87, clause 11.20 or clause 12.3.8 of the Instructions for the design and installation of pile foundations of buildings and structures in Moscow, 2001, then process the pile shaft, reinforce the pile and form the tip in accordance with the requirements of TP 50-180-06. After establishing the lower boundary (sole) of the deepest lying zone of easily compacted soils, the information obtained on the position of the lower boundary of the zone of easily compacted soils is compared with the data of engineering and geological surveys (or the project). Exploratory piles can be either working piles as part of a pile bush, or exclusively exploratory, in the latter case, the diameter of the well can be reduced to a size that allows the source of impulse effects to be immersed in the well, and less expensive material can be used as a hardening fluid. The depth of penetration of the wells of the remaining piles in this cluster is adjusted in accordance with the isohypses of the maximum depth of the soles of the area of easily compacted soils, obtained from the test compaction of the soil in prospecting piles, taking into account the data of engineering and geological surveys.

The depth of penetration of wells for the next pile of piles is adjusted in accordance with isohypses of the maximum depth of the bottom of the zone of easily compacted soils, obtained by compaction of the soil in prospecting piles of neighboring pile piles and taking into account the data of engineering and geological surveys. If necessary, exploratory piles are also carried out in the next bush, the length of which is taken already taking into account the depth of the zone of easily compacted soils installed in neighboring pile bushes.

You can immerse the source of impulse effects immediately on the bottom of the exploration well and impulse effects to detect the lower boundary of the area of easily compacted soils start from the bottom up.

In the manufacture of a pile foundation from drilling piles as part of a continuous pile field in soils containing sporadically represented zones of easily compacted soils, the above-described claimed method is supplemented by the following operations.

Initially, before the mass production of piles of the pile field, based on the analysis of engineering and geological surveys, determine the points at which prospecting piles are made. The depth of the wells for these piles is taken in the design of the pile field according to engineering and geological surveys. At the same time, the accepted length of each prospecting pile should, of course, ensure its penetration into dense soils, underlying the most deeply lying zones of easily compacted soils, found at the nearest points of engineering and geological studies of soils.

The information obtained on the lower boundary of the deepest zone of easily compacted soil of the zone is compared with the data of engineering surveys (or the project). The length of piles located nearby is adjusted according to the results of test soil compaction in an exploratory pile and data from engineering and geological surveys. The distance between exploratory piles and points of engineering and geological studies of soils is chosen depending on the slope of the layers and the consistency of the boundaries between the layers. With unstable boundaries between the layers (slope of more than 0.1) and wedging out of the layers, the grid of prospecting piles should be thickened.

In the manufacture of a pile foundation from drilling piles as part of a continuous pile field in a foundation containing sporadically represented zones of loose sand (or other easily compacted soils), before mass production of the pile field on the basis of an analysis of engineering and geological surveys, the points at which zones of easily compacted soils are found, which occur most deeply. They begin to make exploratory piles in that section of the pile field that is closest to the points of study at which zones of easily compacted soils were found, which lie most deeply. The depth of the wells for these piles is taken in the design of the pile field according to engineering and geological surveys. At the same time, the accepted length of each prospecting pile should, of course, ensure its penetration into dense soils, underlying the most deeply lying zones of easily compacted soils, found at the nearest points of engineering and geological studies of soils. After fixing the lower boundary of the most deeply lying zone of easily compacted soils, the manufacture of a working pile is completed. The production of the following working exploratory piles is carried out in the direction of the nearest points of engineering and geological studies of the base, in which the sole of the area of easily compacted soils lies higher. The length of working exploratory piles is reduced, taking into account the established fact of the occurrence of a zone of easily compacted soils in previously manufactured exploratory piles. The information obtained on the lower boundary of the deepest zone of easily compacted soils is compared with the data of engineering surveys (or the project) and the length of piles located nearby is adjusted. In this case, it is most preferable to use prospecting piles in the future as working piles, since the number of prospecting piles becomes quite significant. A working exploratory pile differs from a working pile only in that in the manufacture of the first one pays more attention to fixing the lower boundary of the area of easily compacted soils.

Pulse tillage under the lower end of the working piles is carried out until the failure of soil compaction. After failure in compaction of the soil is achieved, its density is checked under the lower end of the pile, after which the pile shaft is formed.

The inventive method is illustrated by the following example of its implementation (see drawing).

For the manufacture of a pile field in accordance with the claimed invention, according to the materials of geotechnical surveys of soils, the maximum depths of the soles of the area of loose sand or other weakly soils (zones of easily compacted soils) are determined. Locations of long prospecting piles are determined, for example, in the middle between the nearest points of engineering and geological studies of the base. A well is drilled in the soil with a diameter corresponding to the diameter of the working pile at a selected point in the pile field, the penetration depth of which exceeds the depth of the base of the zone of easily compacted soils, taking into account the reliability coefficient. The well is filled with concrete mixture with the mobility P-4 ... P-5, with the extraction of the tool forming the well. Immersed in a well filled with concrete mixture, equipment with which dynamic impulse effects will be created, providing soil compaction in the local zone surrounding the source of disturbance. As a source of disturbance, a well-known explosive generator can be used that uses binary explosive mixtures in the work, the components of which are not explosives before mixing, for example, hydrogen peroxide and fuel, nitrogen tetroxide and fuel. An electrode system can be used, where a high-voltage electric discharge breakdown periodically occurs between the electrodes in a moving concrete mixture, at the time of breakdown, the electrical energy is converted to other forms, including a shock wave and mechanical displacement of the concrete mixture, or other sources that generate pressure pulses. As a result of the pulsed action of high pressure on the concrete mixture, in the local zone, around the source of disturbance, the soil is compacted, and the mobile concrete mixture instantly fills the volume freed up by soil compaction. At the wellhead, a sharp decrease in the level of concrete mix is clearly observed, usually by a few millimeters. If the pulse action in the well occurs at the place where the layer of easily compacted soils was discovered by the well, at the wellhead there will be a dip in the level of the concrete mix, measured in tens of millimeters, which makes it possible to judge the detection of the zone of easily compacted soils. Submerging a source of disturbance before the bottom of the well with the simultaneous generation of power pulses, the lower boundary of the most deep-seated zone of easily compacted soils is established. This lower boundary could be taken as the maximum depth of adjacent piles, however, the length of the piles should be increased by the required safety factor.

As shown by theoretical studies along with experimental testing, the length of piles, adopted only according to engineering and geological surveys, turned out to be much longer. By clarifying the depth of the lower boundary of the zone of easily compacted soils, within the pile field, the effect of reducing the total length of piles by 10 ... 20% was achieved, which is expressed in a significant reduction in the consumption of materials and the time of manufacture of piles without reducing their bearing capacity.

Thus, for the first time, it is possible to produce a pile foundation from drilling piles, repeating the natural occurrence of strong soils.

In the known method of manufacturing a pile field from drilling piles, additional operations are introduced:

- the selection within the pile field of a number of piles that are made primarily of so-called exploratory piles, the length of which is determined by the materials of engineering and geological surveys at the nearest soil survey points and the results of calculating the bearing capacity of piles on the soil, taking into account the maximum depth of the zone easily compacted soils;

- after filling the well with concrete mixture, until the pile body is formed, carry out test actions at discretely located points along the depth of the well with single pressure pulses, starting from the roof of the most deeply lying zone of easily compacted soils;

- the pulse source is moved along the depth of the well after each impact gradually until the bottom of the well;

- according to the consumption of hardening material, after each pulse, the upper and lower boundaries of the most deeply lying zone of easily compacted soils are fixed;

- form an exploratory pile according to the working pile program;

- based on the information obtained on the maximum depth of the area of easily compacted soils, the data of engineering and geological surveys at the nearest points of soil research and the results of calculating the bearing capacity of piles on the ground, the length of the piles between the nearest prospecting piles is adjusted.

Claims (11)

1. A method of manufacturing a pile base from drilling piles when they are piled up in soils containing soil zones, comprising forming a well in the soil for each pile, supplying it with a flowing hardening material, forming a pile shaft with discrete pulse impulse effects on said material, characterized in that in each pile bush, at least one exploratory pile is made first, mainly at the points farthest from the center of the pile bush, towards the points of engineering and geological survey where the sole of the deepest lying zone of easily compacted soils was installed, the length of exploratory piles is determined by the data of engineering and geological surveys, focusing on the maximum depth of easily compacted soils, and after filling the well with flowing hardening material, discrete pulse impulse actions are carried out along its depth, they are fixed the lower boundary of the most deep-seated zone of easily compacted soils, the obtained information is compared with engineering data zyskany and adjust the depth of penetration wells for piles workers in this bush in accordance with the contour lines of maximum depth legkouplotnyaemyh sole area of ground, the results obtained by compacting soil in the piles exploration, based on the data geotechnical investigations. 2. The method according to claim 1, characterized in that the impact of power pulses along the depth of each well is carried out at located points. 3. The method according to claim 1 or 2, characterized in that the effects of power pulses begin from the roof of the zone of easily compacted soils, found at the nearest point of engineering and geological surveys. 4. The method according to claim 1 or 2, characterized in that the pulse source is immersed in the depth of the well after each impact with a step not exceeding two diameters of the working pile. 5. The method according to claim 1 or 2, characterized in that the impact of power pulses begin from the bottom of the well with the movement of the pulse source up the depth of the well after each impact. 6. The method according to claim 1 or 2, characterized in that the zone of easily compacted soils is detected by the high flow rate of the hardening material (or by a failure to reduce its level at the wellhead) to fill a partially densified zone as a result of discrete single pulses along the length of the well, at the same time, a large flow rate (or decrease) is considered to be a flow rate (or a decrease in level) five or more times higher than a similar flow rate (or a decrease in level) when exposed to a single power impulse in the area of soils not subjected to decompression uw. 7. The method according to claim 1 or 2, characterized in that after fixing the lower boundary of the most deeply lying zone of easily compacted soils, an exploratory pile is formed according to the program for manufacturing working piles. 8. The method according to claim 1 or 2, characterized in that the treatment with pulses of soil under the lower end of the pile is carried out until the failure of soil compaction is achieved, after which the pile shaft is formed. 9. The method according to claim 1 or 2, characterized in that after the failure in compaction of the soil is achieved, the density of the latter is checked under the lower end of the pile. 10. The method according to claim 1 or 2, characterized in that when drilling piles are installed in a pile field, the first exploratory pile is made first, located as close as possible to the point of engineering and geological surveys, in which the sole of the most deep-seated zone of easily compacted soils was installed, the length of exploratory piles is determined according to engineering and geological surveys, focusing on the maximum depth of the zone of easily compacted soils, in this well, the actual position of the sole of the zone of easily compacted soils is determined soil, and each subsequent working pile is made taking into account the established position of the sole of the zone of easily compacted soils in the manufacture of previous piles and data from engineering and geological surveys. 11. The method according to claim 1 or 2, characterized in that when drilling piles are installed in a pile field, an exploratory pile located between the nearest points of engineering and geological surveys, the length of which is determined according to engineering and geological surveys taking into account the maximum depth of the sole, is made first. zones of easily compacted soils at the nearest soil survey points, and the length of piles located between exploratory piles is adjusted according to the results of test compaction of soil in an exploratory pile and engineering data ologicheskih research.

Images