RU2441116C1 - Pile and method of its installation into permafrost soil - Google Patents

Abstract

FIELD: construction. ^ SUBSTANCE: pile comprises a hollow tubular case with an open lower end and an expander attached to the outer wall of the tubular case. The expander is fixed at the level of the open lower end of the tubular case and is made in the form of a spatial curvilinear structure, the section of which with a geometric plane passing via the vertical axis of symmetry of the tubular case is a trapezoid with bases. All points of trapezoid bases lie on spatial surfaces formed by displacement of trapezoid bases along parametric curves. ^ EFFECT: provision of vertical submersion of a pile with account of its bearing capacity. ^ 10 cl, 8 dwg

Description

The group of inventions relates to oil and gas construction, to the field of construction of bearing foundation structures by immersion of tubular support piles and is intended to create pile foundations and regulate their impact on the foundation soils during the construction of buildings and structures for various purposes in areas of permafrost with the preservation of base soils in a natural state throughout the life of a building or structure.

The term “permafrost or cryolithozone distribution area” includes a well-established concept meaning the area of the lithosphere where soils exist in a frozen state continuously for more than several (3-5) years.

The main problem of the construction of pile foundations of an industrial type within the permafrost zone is the significant heterogeneity of the strength characteristics of the base soils both in plan and in section. The mentioned territories are characterized by significant variability of soil temperatures of the engineering-geological section, formed by heat transfer conditions on the Earth's surface. The mechanical characteristics of permafrost soils are mainly determined by their temperature regime, and the amplitude of such changes is such that the same composition of soils at different temperatures can be a liquefied mass of the type "sour cream" and have pronounced plastic properties like "clay" , and constitute "rock category 5". And such soils can be found even within the development spot of a separate building or engineering structure.

Particularly difficult construction conditions associated with the inaccessibility of permafrost, the underdeveloped transport and construction infrastructure make the use of piles unified (identical) in design and a unified method of their immersion, which could be implemented in any soil conditions with a guaranteed result for providing the required bearing capacity. In this sense, screw piles are extremely promising for use, because they provide, due to anchoring in the soil, significant reliability of piles in bearing and pulling loads. Nevertheless, screw piles did not find wide application in northern construction, since the strength properties of permafrost soils require the use of technical means (machines and mechanisms) with significant torque to "overcome" the soil resistance when piling. The construction mechanisms used today allow you to immerse screw piles, but the design of the pile must be "adapted" to the strength characteristics of the base soil. So, for example, piles for thawed soils can be made and shipped with a rather large (up to 800 mm) diameter of the screw part. The most common design is a single-turn anchor. Piles intended for immersion in permafrost soil have a larger angle of inclination of the spiral, a larger number of “turns” of the anchor part, but a significantly smaller diameter of the anchor. Yes, they can be immersed without specialized equipment, but their bearing capacity and stability against the forces of frost heaving are significantly lower.

Known screw pile (RF patent for utility model No. 49841), comprising a hollow barrel with a support element and stiffeners at its upper end and a screw blade on the outer surface of the lower part of the barrel. The lower part of the barrel is made in the form of a molded tip connected to the upper part of the barrel by welding, with an additional blade made on the inner surface of the tip, and the lower end of the tip made conical and equipped with teeth at the end. Immersion of a screw pile is as follows. Pile by screwing is immersed in the leader hole, the diameter of which is equal to the diameter of the trunk. Having reached the scree in the well, an additional helical blade moves the scree soil upward relative to the trunk. The additional screw blade has 1.5-2 turns, while the width of the additional blade is 0.15-0.25 of the inner diameter of the tip.

The result achieved by using the aforementioned construction in the described manner is to facilitate the immersion process by constructing the leader well and by drilling the soil with an additional blade from the inner cavity of the pile. "Significant increase" in the bearing capacity of the pile is ensured by increasing the projection area of the additional screw on a plane perpendicular to the axis of the pile, which in turn can be estimated at 1.5-2.0% when using a blade size of 0.25 d _int . The above gives reason to argue that obtaining the required (design) bearing capacity and stability of the pile in this way is problematic, since the "range of regulation of bearing capacity and stability" does not exceed several percent.

A known method of immersing a tubular pile in permafrost soil (RF patent for the invention No. 2199627), comprising rotating the pile with the formation of an annular heating zone with simultaneous axial feed of the pile with the application of an pressing load to it, characterized in that the axial feed of the pile is controlled from the ratio

where h is the axial feed, mm / rev; P - axial force, kgf; f is the coefficient of friction of steel on the ground; k is the thermal equivalent of work, cal / kgm; k ₁ - specific heat of ice, cal / g · deg; t ⁰ - temperature of frozen soil, ° C; k ₂ - heat of fusion of ice, cal / g; q is the specific gravity of ice, g / mm ³ ; k _L - coefficient of ice content of frozen soil; δ is the wall thickness of the immersed pipe, mm; δ 'is the expansion of the end plane of the friction zone due to radial beats of the pipe end, mm.

The method allows you to immerse in the soil a tubular pile with smooth walls, without an anchor device, since the presented numerical ratio describes the equality of heat generation due to the friction forces of the pile end against the soil and the heat consumption for heating and “melting” of permafrost soil in the annular zone at the lower end of the pile allocated for one revolution of the rotor of the immersion mechanism, taking into account the volume occupied by the pile wall (taking into account the runout), immersed by h millimeters per revolution. Any anchor device located on the lower end of the pile will require a lot of heat, since when implementing the immersion process it will be necessary to "form" an annular thawed zone of a larger diameter than in the aforementioned claims. Also the disadvantages of the method include the inability to immerse piles with an anchor element.

,The closest in technical essence to the claimed group of inventions are the design of a tubular pile with a protective coating and the method of immersion in permafrost soil (RF patent for the invention No. 2202680). The hollow tubular casing is made with an open lower end, the outer wall of the tubular casing at the level of the lower boundary of its protective coating is equipped with an expander made in the form of a direct trihedral prism, the bases of which are rectangular triangles, while one of the ribs α of each base is located along the generatrix of the tubular casing, the other edge β of each base is perpendicular to it, and the values of the edges α and β of the bases of the prism of the expander are determined from the relations

,

- наружный диаметр трубчатой сваи, м; H_n - расстояние от нижнего торца трубчатой сваи до расширителя, м;

- плотность оттаянного грунта, кг/м³; g - ускорение свободного падения, м/с²;

- коэффициент внутреннего трения грунта, ξ₀ - коэффициент бокового трения грунта, L_V - теплота таяния единицы объема мерзлого грунта, Дж/м³, δ_покр - толщина покрытия, м. Способ погружения трубчатой сваи с защитным покрытием в многолетнемерзлый грунт включает одновременное воздействие на трубчатую сваю крутящего момента и осевого усилия до образования в грунте под торцом трубчатой сваи и вдоль ее стенок оттаянной зоны в виде полого цилиндра и заглубление в нее трубчатой сваи. В процессе погружения трубчатой сваи вдоль ее стенок в интервале от дневной поверхности до нижней границы защитного покрытия создают зону оттаянного грунта, толщина которой превышает толщину зоны оттаянного грунта вдоль стенок трубчатой сваи ниже защитного покрытия не меньше, чем на толщину защитного покрытия.where α, β are the sizes of the edges of a straight trihedral prism, m; V is the immersion speed of the tubular pile, m / min; ω is the rotation speed of the tubular pile, rpm

- the outer diameter of the tubular pile, m; H _n is the distance from the lower end of the tubular pile to the expander, m;

- the density of thawed soil, kg / m ³ ; g is the acceleration of gravity, m / s ² ;

is the coefficient of internal friction of the soil, ξ ₀ is the coefficient of lateral friction of the soil, L _V is the thawing heat of a unit volume of frozen soil, J / m ³ , δ _cover is the thickness of the coating, m. The method of immersing a tubular pile with a protective coating in permafrost includes simultaneous exposure on a tubular pile of torque and axial force until a thinned pile is formed in the soil under the end of the pipe and along its walls in the form of a hollow cylinder and a tubular pile is buried in it. When a tubular pile is immersed along its walls in the interval from the day surface to the lower boundary of the protective coating, a thawed soil zone is created whose thickness exceeds the thickness of the thawed soil zone along the walls of the tubular pile below the protective coating not less than by the thickness of the protective coating.

The known solution allows you to immerse a tubular pile with an expander in the form of a direct trihedral prism by rotating the pile with the formation of an annular heating zone under the lower end and under the expander. The disadvantage of this method is that the objective function of the method does not provide for the use of an expander as an anchor device after immersing the piles in the ground and restoring the natural temperatures of permafrost. The extender is used only to ensure the safety of the insulating coating within the active seasonal soil layer near the upper end of the pile.

The task to which the claimed group of technical solutions is directed is to create a unified design of an anchor pile, immersed in the ground, using the minimum number of technological operations, the minimum number and nomenclature of construction equipment, providing the possibility of obtaining a given (design) bearing capacity and stability against frost forces heaving by changing the geometric parameters of the pile. Another objective is to create a method of installing piles, providing immersion piles in the soil with any mechanical characteristics found in the developed territories of permafrost distribution.

The technical result achieved by using the claimed group of inventions is to ensure vertical immersion of the pile, taking into account its bearing capacity.

The problem is solved in that in a pile, including a hollow tubular body with an open bottom end and an expander attached to the outer wall of the tubular body, according to the technical solution, the expander is fixed at the level of the open bottom end of the tubular body and is made in the form of a spatial curvilinear structure, the cross section of which is geometric the plane passing through the vertical axis of symmetry of the tubular body represents a trapezoid with the bases α and β, while all the points of the bases of the trapezium lying in spatial surfaces formed trapezoid base moving to the parametric curve:

;

;

и

;

;

and

;

;

где

;

;

Where

x _α , y _α , z _α - spatial coordinates for points on the surface of the expander described by the lower base of the trapezoid;

x _β , y _β , z _β - spatial coordinates for points on the surface of the expander described by the upper base of the trapezoid;

d _nar - the outer diameter of the tubular body, m;

L _races - the length of the projection of the height of the expander on the axis of symmetry of the tubular body, m;

h _Tr - the height of the trapezoid, m;

φ∈ [0, φ _max ] - parameter that describes the angle of rotation of the axial section plane of the expander, rad .;

φ _max - the maximum absolute value of the parameter φ, rad .;

δ is the wall thickness of the tubular body, m

и β∈[0, α] с возможностью обеспечения заданных прочностных характеристик сваи. Боковые стороны трапеции могут представлять собой вогнутые кривые. Численные значения величин d_нар, φ_max, δ, h_тр, L_рас могут быть выбраны из следующих диапазонов:The numerical values of α and β are selected from the ranges

and β∈ [0, α] with the ability to provide the specified strength characteristics of the piles. The sides of the trapezoid may be concave curves. The numerical values of d _dar , φ _max , δ, h _tr , L _races can be selected from the following ranges:

d _nar - from 0.1 to 0.4 m;

δ - from 6 to 12 mm;

h _Tr - from 0.0 · d _drug , up to 1.5 · d _drug ;

φ _max - from 0 to 100π;

до

L _races - from

before

with the ability to ensure and regulate the design bearing capacity of the pile and its resistance to frost heaving forces in accordance with the following ratios:

;

;

for pressing load and

for pulling out where

F _{d, du} - bearing capacity of piles, hardware;

γ _i - reliability coefficients: γ _af - coefficient depending on the type of freezing surface, γ _c - reliability coefficient according to the conditions of the pile, γ _t - temperature coefficient;

R - specific design resistance of frozen soil to normal pressure, tf / m ² ;

R _sh — specific design resistance of permafrost soil to shear along the surface of freezing with soil, tf / m ² ;

R _{af, i} is the calculated resistance of frozen soil to shear along the lateral surface of freezing of the tubular pile body with permafrost soils, tf / m ² ;

за один оборот ротора вращающего механизма посредством попеременного изменения крутящего момента и осевого усилия, гдеA _{af, i is} the freezing surface area of the i-th soil layer with the lateral surface of the tubular pile body, m ² . The pile can also be equipped with a baking powder attached to the expander from the side of its lower end surface and made in the form of a figure similar in shape to a triangular pyramid with at least one curved face, while the base of the pyramid is located on the lower end surface of the expander, curvature the curved face of the pyramid corresponds to the curvature of the tubular body, and the height of the pyramid h _{pr is} set in the range of values from 0.6 h _tr to 1.8 h _tr , where h _tr is the trapezoid height, m. The section of the tubular pile body, located The pivot between the zone of placement of the lower end surface of the expander and the lower end surface of the pile is a truncated cone, while the curved edges of the pyramid of the baking powder are made curved in the form of a helicoid screw, and the top of the baking powder is located on the generatrix of the truncated cone near the lower end of the tubular body. The problem is also solved in that in a method of installing a pile, including drilling a leader well with a diameter smaller than the inner diameter of the hollow tubular body of the pile, installing the pile in the leader well, simultaneously applying torque and axial force to the pile until the pile is immersed at the design depth , filling the inner cavity of the pile with cement-sand mortar, thawed drilled soil or other soil or sand-cement mortar, and holding the latter until it freezes with an array of permafrost soils comrade, according to the technical solution in the process of simultaneous impact of torque and axial force ensure the achievement of axial feed equal to

per revolution of the rotor of the rotating mechanism by alternating changes in torque and axial force, where

L _races - the length of the projection of the height of the expander on the axis of symmetry of the tubular body, m;

φ∈ [0, φ _max ] - parameter that describes the angle of rotation of the axial section plane of the expander, rad .;

φ _max - the maximum absolute value of the parameter φ, which describes the angle of rotation of the plane of the axial section of the expander, rad. Before installing the piles on the walls of the leader well, they have a thermal effect until the temperature of the beginning of thawing of permafrost soil is reached.

. При возобновлении воздействия обеспечивают заданную производительность погружения сваи, устанавливая осевую подачу в соответствии со следующим соотношением:As an option to solve the problem, a method for installing a pile is claimed, including drilling a leader well with a diameter smaller than the inner diameter of the hollow tubular body of the pile, installing the pile in the leader well, simultaneously applying torque and axial force to the pile until the pile is immersed at the design depth, filling the internal cavity of the pile with cement-sand mortar, thawed drilled soil or other soil or sand-cement mortar and holding the latter until it freezes with an array of frozen soils, in this case, according to the technical solution, during the simultaneous impact of torque and axial force when the pile is stopped, the axle load is removed and the pile is removed from the soil by applying an opposite directional torque to it, after which the simultaneous effect of torque and axial force is resumed with an increase in the rotation speed of the mechanism used for immersion, at the same time, the soil is thawed under the lower end surface of the pile and g of its lateral surface to form thawed annular zone outer radius which is at least

. When the impact is resumed, they provide the desired productivity of pile immersion by setting the axial feed in accordance with the following ratio:

, где

where

η - axial feed of the pile into the ground, m / s;

Q _f - specific heat of heating thawing soil, J / m ³ ;

f is the coefficient of friction between the pile and the soil surface;

P _c - pressure exerted by the pile on the soil surface, Pa.

The claimed group of inventions is illustrated by the following drawings.

Figure 1 presents the image of the piles installed in the ground.

Figure 2 schematically shows a portion of the tubular pile body with an expander, the vertical section of which at each point is a trapezoid.

Figure 3 schematically shows the shaping of the expander in the form of a trapezoid.

Figure 4 schematically shows the shaping of the expander in the form of a rectangle.

Figure 5 schematically shows the shaping of the expander in the form of a triangle.

Figure 6 schematically shows the shaping of the expander in the form of a triangle (degenerate trapezoid) with concave lateral sides.

Figure 7 schematically shows the shaping of the expander in the form of a trapezoid with a pyramidal baking powder attached to the lower end surface of the expander.

On Fig presents a portion of the tubular pile body, made in the form of a truncated cone.

The positions in the drawings indicate:

1 - pile, 2 - tubular body, 3 - expander, 4 - baking powder.

и β∈[0, α]. Боковые стороны трапеции, могут быть выполнены как в форме прямых, так и вогнутых линий, при этом вогнутость направлена внутрь трапеции. Размеры оснований трапеции выбраны таким образом, чтобы, с одной стороны, обеспечить равнозначные прочностные характеристики отдельных частей сваи как единой конструкции, обеспечив при этом одновременное выполнение требований по уменьшению сопротивления разрезанию грунта разрыхлителем при погружении сваи, по обеспечению развитой поверхности трения металла о грунт для обеспечения образования кольцевой талой зоны вокруг внешней и внутренней поверхностей трубчатого корпуса (2), а с другой стороны, обеспечить достаточную площадь заанкеривания расширителя (3) сваи (1) в многолетнемерзлые грунты после восстановления их естественных температур. На внешней поверхности вблизи нижнего торца трубчатого корпуса (2) встык с нижней торцевой трапециевидной поверхностью расширителя (3) может быть закреплен разрыхлитель (4), с геометрической точки зрения представляющий собой пирамидальную конструкцию, основание которой размещено на торцевой трапециевидной грани поверхности расширителя (3), а одна из боковых граней разрыхлителя (4) выполнена криволинейной, при этом кривизна этой грани соответствует кривизне трубчатого корпуса (2).The pile (1) is a tubular metal structure comprising a tubular body (2) and an expander (3) made, for example, of steel. The tubular body (2), piles are made in the form of a hollow cylinder with an open upper and lower end and wall thickness δ. Near the lower end part of the tubular body (2) of the pile (1), an expander (3) is rigidly fixed on its outer surface, for example, by welding or casting, made in the form of a curved spiral figure encircling the tubular body (2) of the pile (1) on plot length L _ra . The number of full revolutions of the expander (3) around the tubular body (2) is equal to φ _max . The cross section of each section of the expander (3) by a plane passing through the axis of symmetry of the tubular body (2), in the general case, is a trapezoid whose bases (α and β) are parallel to the axis of symmetry of the tubular body and can be varied in the range of values

and β∈ [0, α]. The sides of the trapezoid, can be made in the form of straight or concave lines, while the concavity is directed inside the trapezoid. The dimensions of the trapezoid bases are selected in such a way as to ensure, on the one hand, equivalent strength characteristics of the individual parts of the pile as a single structure, while ensuring that the requirements for reducing the cutting resistance of the soil by the baking powder while immersing the pile are met, to ensure a developed surface of metal friction against the soil to ensure the formation of an annular thawed zone around the outer and inner surfaces of the tubular body (2), and on the other hand, to provide a sufficient area of zaanke tearing the expander (3) piles (1) into permafrost soils after restoring their natural temperatures. On the outer surface near the lower end of the tubular body (2), a baking powder (4) can be fixed butt to the lower end trapezoidal surface of the expander (3), which from a geometric point of view is a pyramidal structure, the base of which is placed on the end trapezoidal surface of the expander (3) and one of the side faces of the baking powder (4) is made curved, while the curvature of this face corresponds to the curvature of the tubular body (2).

The lower part of the housing can be made in the form of a truncated cone or a straight cylinder.

The bearing capacity of the pile and its resistance to frost _{heaving are regulated} by a reasonable choice of the numerical values of the geometric parameters of the tubular body d _bunk , δ and the expander φ _max , h _tp , L from the range of values

d _nar - from 0.1 to 0.4 m .;

δ - from 6 to 12 mm;

h _Tr - from 0.0 · d _Nar to 1.0 · d _Nar ;

φ _max - from 0 to 100 π;

до

;L _races - from

before

;

until the design values of the pressing and pulling forces are obtained in specific ground conditions, taking into account design coefficients of "reliability".

An example of regulation of the bearing capacity of piles

The engineering-geological section of the considered construction site is represented within the active layer to 1.6 meters by icy loams (i = 0.40), slightly saline (D _sal = 0.77), with average temperatures at the time of maximum (1.6 m) thawing t = + 0.4 ° C. Further, to a depth of 4.0 m, sandy loam, ice content i = 0.25, salinity D _sal = 0.24, temperature t = -2.3 ° C. From a depth of 4.0 m and lower in the section, loamy sandy loam (i = 0.16), non-saline (D _sal = 0.06) with a temperature of t = -2.4 ° С.

In the area under consideration, a pile foundation is laid, which would absorb the load from the structure, equal to F _indentation = 18.0 tf per unit pile. This load level is most characteristic for the foundations of frame industrial buildings, complex technological piping, individual foundations of technological equipment. Metal pipes with a length L = 6.0 m, diameter d _nar = 0.219 m and wall thickness δ = 0.008 m were used as a tubular casing of piles.

The pile foundation, at the same time as ensuring the perception of the design load, should “protect” the structure from seasonal deformation of piles under the influence of frost heaving forces, equal, for the considered engineering and geotechnical conditions, to the value of F _pull-outs = 12.9 tf.

In accordance with SNiP 2.02.04-88, the values of the reliability coefficients are γ _af = 0.7 (a coefficient depending on the type of freezing surface), γ _c = 1.0 (reliability coefficient according to the conditions of the pile), γ _t = 0.8 (temperature coefficient); values of specific design resistance of frozen ground to normal pressure in tf / m ² (R), specific design resistance of permafrost to shear on the freezing surface with permafrost in tf / m (R _sh ) and design resistance of frozen ground to shear on the lateral surface of freezing of the tubular pile with permafrost soils in tf / m ² (R _{af, i} ) SNiP 2.02.04-88 are calculated and shown in the table.

The height of the trapezoid of the expander is selected in the range of absolute values near the minimum limit, for example, h _tr = 0.04 · d _nar = 0.219 · 0.04 = 0.008 m; the dimensions of its bases α = β = δ = 0.008 m. The length of the expander L _ras = 0.40 m provides φ _max equal to 720 °, that is (φ _max = 4π).

(слой 1 не является многолетнемерзлым, он сезонно-талый).In this case, the total freezing surface area within two permafrost layers of the engineering-geological section (lines 2 and 3, Table 1) is equal to

(layer 1 is not permafrost, it is seasonally thawed).

и

Moreover, the freezing area of the side surface of the pile body with soils within each engineering-geological element (layer) is equal to _{Af, 1} = 0.55 m ² (the rock does not freeze with the surface of the pile within the seasonal thawing layer),

and

respectively.

The forces holding the pile in the soil due to their freezing with its body are equal outside the area of the expander:

The forces counteracting the displacement of the pile down vertically due to the application of loads from the foundation structure:

The forces that counteract the displacement of the pile up along the vertical axis due to the forces of frost heaving of the soil of a seasonally thawed layer:

The forces holding the pile in the soil due to the anchoring of the expander and the action of forces that prevent mixing of the expander along the axis of the pile:

As a result, taking into account the safety factors, the pile of the proposed design has a total bearing capacity of the pressing load equal to:

and has a stable position against the effects of pulling loads:

Thus, the pile with the selected characteristics (d _nar = 0.219 m, φ _max = 4π, δ = 0.008 m, h _tr = 0.008 m, L _ra = 0.40 m) does not provide design indicators for the pressing load. It is necessary to adjust the geometrical parameters of the expander to ensure the designed parameters.

However, the absence of an expander as such leads to the following results. Consider a load-bearing capacity of the pile at _nar d = 0.219 _{m, φ max = 4π, δ =} 0,008 m, h _mp = 0.0 m, L = 0.0 m _races.

In this case, in comparison with the previous example, the value of F will increase by an amount corresponding to the freezing forces of the material of the pile body with soils within the surface of the body where the expander was previously placed

The remaining components of the bearing capacity of the piles are equal to:

As a result, taking into account the safety factors, a pile without a conservator has a total bearing capacity of the pressing load equal to:

and has a stable position against the effects of pulling loads:

Thus, the addition of a tubular pile body with a very small extender leads to a 35% increase in the pile's bearing capacity and its stability against seasonal frost heaving forces, all other things being equal (soil characteristics, pile body dimensions, etc.).

The process of adjusting the bearing capacity is provided by changing the geometric characteristics of the expander in the specified ranges.

So, for example, in this case, an increase in h by 20 mm, to a value of 0.028 m (0.13 · d _nar ) gives a positive result and the total pile holding forces increase to the planned design values, namely

As a result, the total bearing capacity for the pressing load is equal to:

and has a stable position against the effects of pulling loads:

The required design values for the pressing load have been achieved. The characteristics of the piles are set equal to d _nar = 0.219 m, φ _max = 4π, δ = 0.008 m, h _tr = 0.025 m, L _ra = 0.4 m.

The inventive method is implemented as follows.

The main factor in the installation of the pile is the provision of a certain axial feed for vertical immersion of the pile. The leader well is pre-drilled, the diameter of which is smaller than the inner diameter of the pile body. The diameter of the leader well is selected from the range from 0 to d _nar- δ depending on the state of permafrost soils. In this case, the minimum diameter is mainly used for finely dispersed plastic-frozen soils occurring at a temperature corresponding to the beginning of the transition of pore moisture to thawed state, and the maximum is used for permafrost soils with a significant difference between the natural occurrence temperature and the temperature of thawing onset.

метров за один оборот ротора вращающего механизма посредством попеременного изменения крутящего момента и осевого усилия. До установки сваи в лидерную скважину на стенки последней может быть оказано тепловое воздействие до достижения температуры начала оттаивания вечномерзлого грунта. Для теплового воздействия может быть использован любой протяженный тепловыделяющий источник, например шланг с отверстиями в боковых стенках для подачи перегретого пара, или разогретая масса выбуренного грунта. Таким образом, при обеспечении указанной осевой подачи сваю погружают на требуемую глубину, после чего ее полый корпус, при необходимости, заполняют песчано-цементным или иным фиксирующим раствором и выдерживают до смерзания с грунтом, после чего считают установку завершенной.A pile of the claimed design is installed in the leader well, after which axial (along the vertically located axis of symmetry of the pile body) force and torque are applied to the pile. At the same time, such a ratio of the applied axial load and torque is ensured that the axial feed (immersion speed) is equal to

meters per revolution of the rotor of the rotary mechanism through alternating changes in torque and axial force. Before installing the piles in the leader well, the walls of the latter can have a thermal effect until the temperature of the beginning of thawing of permafrost soil is reached. For heat exposure, any extended heat source can be used, for example, a hose with holes in the side walls for supplying superheated steam, or a heated mass of drilled soil. Thus, while ensuring the indicated axial feed, the pile is immersed to the required depth, after which its hollow body, if necessary, is filled with sand-cement or other fixing solution and kept until freezing with soil, after which the installation is considered complete.

, достигая требуемой производительности погружения сваи (осевой подачи) посредством установления осевого усилия в соответствии со следующим соотношением:

, гдеIn the case when the pile sinking during the simultaneous action of the torque and the axial force is stopped, that is, it is not possible to provide the specified value of the axial feed, the pile is removed by stopping the axial force and changing the direction of the torque. After the piles are removed to the surface, the simultaneous effect of torque and axial force resumes with an increase in the rotation speed of the rotor mechanism used for immersion, for example, the KATO installation of the PF-1200-YSVIII model. In this case, due to friction against permafrost rocks of the lower end of the tubular pile and the lateral surface of the expander, the soil is thawed under the lower end of the pile and around its lateral surface with the formation of an annular zone, the outer radius of which exceeds an amount equal to

while achieving the required pile driving performance (axial feed) by setting the axial force in accordance with the following ratio:

where

η - axial feed of the pile into the ground, m / s;

Q _f - specific heat of heating thawing soil, J / m ³ ;

f is the coefficient of friction between the pile and the soil surface;

P _c - pressure exerted by the pile on the soil surface, Pa.

метра за один оборот ротора буровой установки. Поддерживая установившуюся подачу, завершают процесс погружения сваи на проектную глубину.Consider a specific example of the implementation of the method of installing piles. A metal pile with a total length of 10 m with the proposed design of the expander, having the following geometric parameters d _nar = 0.325 m, φ _max = 4π, δ = 0.008 m, h _tr = 0.03 m, L _ra = 0.4 m, α = 0.008 m, β = 0.004 m. Immerse in icy hard frozen loam with a specific heat of thawing Q _f = 101136 · 10 ³ J / m ³ . To immerse piles, KATO self-propelled drilling rig model PF-1200-YSVIII is used. Initially, a standard drilling tool with a diameter of 300 mm is fixed in the rotary mechanism of the drilling rig and the leader is drilled to the depth of the design position of the upper end of the expander. Next, the drilling tool is removed from the rotary mechanism and the internal cavity of the leader well is heated with a steam needle until the temperature of the start of thawing of the rocks composing the walls of the leader well is reached. Such a warm-up allows you to translate into a plastic-frozen state soils composing the well walls to a depth exceeding 50 mm. To ensure uniform heating or when planning a long break between drilling a leader well and sinking a pile, another method of heating can be used, which consists in filling (filling) the leader well with thawed drilled soil, which allows to maintain a plastic-frozen state of soils composing the well walls for a longer time time. After heating the well walls, a pile is installed in the rotary mechanism of the drilling machine, applying an axial force equal to, for example, 1/3 of the working range of the KATO hydraulic system model PF-1200-YSVIII, while applying a torque, while achieving alternating torque and axial control efforts to provide axial feed piles equal to

meters per revolution of the rotor of the drilling rig. Maintaining a steady feed, complete the process of immersion piles to the design depth.

Такой размер зоны протаивания в рассматриваемых суглинках (Q_f=101136·10³ Дж/м³) обеспечивает, например, при осевом усилии 12 тс (3/4 рабочего диапазона гидравлической системы буровой установки "Като" используемой модели), то есть при давлении на грунт нижним торцом корпуса и боковой поверхностью расширителя, равном P_c=2950 кПа, при значениях коэффициента трения металла о многолетнемерзлый мелкодисперсный грунт f=0,45, осевую подачу (скорость погружения), равную:In the case when it is not possible to establish and maintain the required feed rate during the entire immersion process due to insufficient working range of axial loads and the torques of the mechanism used for immersion, the immersion process is temporarily interrupted, the axial load is removed and the pile is removed from the ground by applying to it oppositely directed torque. Further, after the piles are removed to the surface, the simultaneous effect of torque and axial force is renewed with an increase in the rotational speed of the rotary mechanism of the drilling rig, while the required immersion performance is set mainly by axial force, providing thawing of the soil under the lower end of the pile and around its side surface with the formation of an annular zone whose outer radius exceeds a value equal to

This size of the thawing zone in the loams under consideration (Q _f = 101136 · 10 ³ J / m ³ ) provides, for example, with an axial force of 12 tf (3/4 of the working range of the hydraulic system of the Kato drilling rig of the model used), that is, with pressure on the ground with the lower end of the casing and the lateral surface of the expander equal to P _c = 2950 kPa, with the values of the coefficient of friction of the metal on permafrost fine soil f = 0.45, the axial feed (immersion speed) equal to:

за один оборот роторного механизма буровой установки.

per revolution of the rotary mechanism of the drilling rig.

The working range of the Kato rotor model PF-1200-YSVIII provides from 0 to 54 revolutions per minute. The total time spent on immersion of the pile in question can be estimated at 10–25 minutes.

The average immersion speeds of the experimental piles, which are a hollow tubular metal casing without an expander and without a leader well, at the Pioneer Gas Supply Pipeline of the Prombaza GP2 Site of the Bovanenkovskoye Field amounted to approximately 1 m / min at a rotor speed of 15-25 rpm.

Thus, the proposed device and the method of its installation can reduce the time and material costs for the construction of pile foundations in the permafrost zone. In addition, the device and methods possess the properties of regional universality, since they do not require a technology change when moving from plastic-frozen to hard-frozen areas of spreading of permafrost rocks of a merging type, are applicable for areas of a buried roof of permafrost, provide for the use of only one mechanism in the technological cycle and minimization of “wet” processes. "

Claims (10)

1. Pile, comprising a hollow tubular body with an open bottom end and an expander attached to the outer wall of the tubular body, characterized in that the expander is mounted at the level of the open lower end of the tubular body and is made in the form of a spatial curvilinear structure, the cross section of which is a geometric plane passing through the vertical axis of symmetry of the tubular body represents a trapezoid with bases α and β, while all points of the bases of the trapezoid lie on spatial surfaces formed by x displacement of the trapezium bases parametric curves:

and

where x _α , y _α , z _α , are the spatial coordinates for the points on the surface of the expander described by the lower base of the trapezoid;
x _β , y _β , z _β - spatial coordinates for points on the surface of the expander described by the upper base of the trapezoid;
d _nar - the outer diameter of the tubular body, m;
L _races - the length of the projection of the height of the expander on the axis of symmetry of the tubular body, m;
h _Tr - the height of the trapezoid, m;
φ∈ [0, φ _max ] - parameter that describes the angle of rotation of the axial section plane of the expander, rad;
φ _max - the maximum absolute value of the parameter φ, rad;
δ is the wall thickness of the tubular body, m 2. The pile according to claim 1, characterized in that the numerical values of α and β are selected from the ranges

and β∈ [0, α] with the ability to provide the specified strength characteristics of the piles. 3. The pile according to claim 2, characterized in that the sides of the trapezoid are concave curves. 4. The pile according to claim 1, or 2, or 3, characterized in that the numerical values of the values of d _nar , φ _max , δ, h _tr , L _races are selected from the following ranges:
d _nar - from 0.1 to 0.4 m;
δ - from 6 to 12 mm;
h _Tr - from 0.0 · d _nar to 1.5 · d _nar ;
φ _max - from 0 to 100π;
L _races - from

before

with the ability to ensure and regulate the design bearing capacity of the pile and its resistance to frost forces in accordance with the following ratios:

for pressing load and

for pulling,
where F _{d, du} - bearing capacity of piles, hardware;
γ _i - reliability coefficients: γ _af - coefficient depending on the type of freezing surface, γ _c - reliability coefficient according to the conditions of the pile, γ _t - temperature coefficient;
R - specific design resistance of frozen soil to normal pressure, tf / m ² ;
R _sh — specific design resistance of permafrost soil to shear along the surface of freezing with soil, tf / m ² ;
R _{af, i} is the calculated resistance of frozen soil to shear along the lateral surface of freezing of the tubular pile body with permafrost soils, tf / m ² ;
A _{af, i} is the freezing surface area of the i-th soil layer with the lateral surface of the tubular pile body, m ² . 5. The pile according to claim 1, or 2, or 3, characterized in that it is provided with a baking powder attached to the expander from the side of its lower end surface and made in the form of a figure in a shape close to a triangular pyramid with at least one a curved face, while the base of the triangular pyramid is located on the lower end surface of the expander, the curvature of the curved face of the pyramid corresponds to the curvature of the tubular body, and the height of the pyramid h _{tr is} set in the range from 0.6 h _tr to 1.8 h _tr , where h _tr - trapezoid height, m. 6. The pile according to claim 5, characterized in that the portion of the tubular pile body located between the area of the lower end surface of the expander and the lower end surface of the pile is a truncated cone, while the curved edges of the pyramid of the baking powder are made curved in the form of a helicoid screw, and the top the baking powder is located on the generatrix of the truncated cone near the lower end of the tubular body. 7. A method of installing a pile in permafrost soil, including drilling a leader well with a diameter smaller than the inner diameter of the hollow tubular pile body, installing the pile in the leader well, simultaneously applying torque and axial force to the pile until the pile is immersed at the design depth, filling the internal cavity piles cement-sand mortar thawed with drilled soil or other soil or sand-cement mortar and aging piles until it freezes with an array of permafrost soils, characterized in that in otsesse simultaneous effects of torque and axial force achievement provide axial feed equal magnitude

for one rotation of the rotor of the rotating mechanism by alternating changes in torque and axial force,
where L _ra - the projection length of the height of the expander on the axis of symmetry of the tubular body, m;
φ∈ [0, φ _max ] - parameter that describes the angle of rotation of the axial section plane of the expander, rad;
φ _max - the maximum absolute value of the parameter φ, which describes the angle of rotation of the plane of the axial section of the expander, rad. 8. The method of installing piles according to claim 7, characterized in that before installing the piles on the walls of the leader well, they exert a thermal effect until the temperature of the beginning of thawing of permafrost is reached. 9. A method of installing a pile in permafrost soil, including drilling a leader well with a diameter smaller than the inner diameter of the hollow tubular pile body, installing the pile in the leader well, simultaneously applying torque and axial force to the pile until the pile is submerged to the design depth, filling the internal cavity piles cement-sand mortar thawed with drilled soil or other soil or sand-cement mortar and aging piles until it freezes with an array of permafrost soils, characterized in that in the process of simultaneous action of torque and axial force when the pile is submerged, the axial load is removed and the pile is removed from the soil by applying an opposite directional torque to it, after which the simultaneous effect of torque and axial force is resumed with an increase in the rotation speed of the mechanism used for immersion, this is ensured by the thawing of the soil under the lower end surface of the pile and around its lateral surface with the formation of a thawed annular zones with an external radius of at least

. 10. The method of installing piles according to claim 9, characterized in that when the action is resumed, they provide a predetermined pile diving performance by setting the axial feed in accordance with the following ratio:

,
where η is the axial feed of the pile into the ground, m / s;
Q _f - specific heat of heating thawing soil, J / m ³ ;
f is the coefficient of friction between the pile and the soil surface;
P _c - pressure exerted by the pile on the soil surface, Pa.

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