RU2537463C1 - Construction method of pile screw-blade foundation of structure, and its arrangement - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: pile foundation consists of a field of screwed-in screw-blade piles, each of which consists of a steel tubular tip with screw-blade winding of blade ascending under a cone in an upward direction with maximum diameter D_max on an upper end. The pile tip is attached throughout the height with sections of hollow pipes, on the upper end of the column of which there mounted is a foundation frame after the cavity of the pipe column is filled with cement mortar or concrete. A screw blade has a semi-spherical support surface, the angle of semi-contact of which to soil is an angle of soil internal friction in a disturbed state φ_k=φ_H. Diameter D_max of the pile is chosen based on the carrying capacity of soil, the value of initial (the first) critical load for which is assumed based on the specified mathematical relationship, and the pile is screwed into soil to depth h≤c_building/γ_building, where γ_building - specific soil weight.

EFFECT: increasing carrying capacity of a pile and stability of a pile foundation.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of construction of pile foundations of low-rise structures constructed on low-strength soil bases.

и соответствующее нормативное сопротивление грунта $$R^{н}=\frac{\pi \left(\gamma D/4+\gamma h+c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h>p_{Ф}$$

на подстилающий слабое основание прочный грунт, где р_Ф - давление под лопастью сваи от сооружения [1].There is a method of constructing a pile screw-blade foundation of a low-rise residential building on soils with low bearing capacity, which consists in the fact that they conduct engineering surveys at the construction site in depth h of the soil foundation with the determination of the thickness of the upper layer of the weak foundation and the establishment of the physical parameters underlying the weak foundation of the more durable soil: angle φ _{str of} internal friction, with _str - structural specific adhesion, γ _str - specific gravity, to the depth to failure in the underlying soft soil the base is screwed onto the working tip of the screw-blade pile foundation by increasing it in height from thick-walled pipes joined into the column, the inner cavity of the column and tip pipes is filled with cement mortar or concrete and a grillage is installed, while the diameter D of the screw blade of the tip and the pitch t of its winding are made constant in height tip, and the diameter of the blade is selected with the area of its supporting surface, providing a safe initial (first) critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}=\frac{\pi \left(\gamma h-c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h$$

and corresponding regulatory soil resistance $$R^n=\frac{\pi \left(\gamma D/\mathrm{four}+\gamma h+c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h>p_F$$

on solid ground underlying a weak base, where p _Ф is the pressure under the blade of the pile from the structure [1].

, безопасное для грунтового основания под фундаментом сооружения.A disadvantage of the known method of constructing a pile screw-blade foundation is the complexity of screwing it to a depth, for example, of a freezing weak soil base due to the large resistance of the soil to cutting with the long frontal edges of the pile blade and the large friction of the soil against its lateral surface. So far, in the "Soil Mechanics" the true value of the initial (first) critical pressure has not been established $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

safe for soil under the foundation of the structure.

разрушения грунта под краями фундамента, поэтому для свайных винтолопастных фундаментов различного диаметра D для разновидностей грунтов опытным путем определяют несущую способность испытываемых разновидностей грунтовых оснований.The expression of N.P. Puzyrevsky for extreme critical pressure $$p_{}^{}$$$${}_2^{\mathrm{to}RP}$$

destruction of the soil under the edges of the foundation, therefore, for pile screw-blade foundations of various diameters D for varieties of soils, the carrying capacity of the tested varieties of soil bases is experimentally determined.

и соответствующее нормативное сопротивление грунта $$R^{н}=\frac{\pi \left(\gamma D/4+\gamma h+c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h>p_{Ф}$$

на подстилающий слабое основание прочный грунт, где р_Ф - давление под лопастью сваи от сооружения, а несущую способность винтолопастной сваи в соответствии с таблицей (таблица 1).There is a method of constructing a pile screw-blade foundation, which consists in the fact that they carry out engineering surveys of the soil foundation of the foundation of the structure, determine the value of φ _pp from the depth h of the active compressible thickness and from _p - the angle of internal friction and the specific adhesion of the soil to the undisturbed structure, γ _p - specific gravity , the pile tip is made with a straight D-varir diameter increasing in height in the cross section of a screw blade with a constant pitch t, the pile tip is screwed into a soil base the rotation and progressive immersion by step t for one revolution in the soil mass at the design depth and further to failure, as the screw-blade tip is immersed in the soil, it is expanded with a column of thick-walled pipes joined in height, the pipe string after immersion in the soil of the tip is poured with cement mortar or concrete , the upper end of the pipes is closed with a grillage, while the maximum diameter D _{max of the} screw blade of the tip is taken with the size of the area of the supporting surface of the upper turn, providing the initial (first) crit ground pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}=\frac{\pi \left(\gamma h-c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h$$

and corresponding regulatory soil resistance $$R^n=\frac{\pi \left(\gamma D/\mathrm{four}+\gamma h+c\cdot ctg\varphi \right)}{ctg\varphi +\varphi -\pi /2}+\gamma h>p_F$$

on solid ground underlying a weak foundation, where p _Ф is the pressure under the blade of the pile from the structure, and the bearing capacity of the propeller blade in accordance with the table (table 1).

Table 1 Type of soil Plasticity for clay The calculated resistance R ⁿ kg / cm ² Bearing capacity of piles (89 × 300), ton, at the depth of immersion of the blade (m) 1,5 m 2.0 m 2.5 m 3.0 m one 2 3 four 5 6 7 Loess soft plastic 1,0 2.2 2.9 3.6 4.3 Clay semi-solid 6.0 4.7 5,4 6.0 6.7 stiff 5,0 4.2 4.9 5,6 6.3 soft plastic 4.0 3,7 4.4 5,0 5.8 Sandy loam and loam semi-solid 5.5 4.4 5.1 5.8 6.5 stiff 4,5 3.9 4.6 5.3 6.0 soft plastic 3,5 3,5 4.2 4.8 5.5 Sands medium fifteen 9.0 9.7 10,4 11.1 small 8.0 5,6 6.3 7.0 7.7 dusty 5,0 4.2 4.9 5,6 6.3 additionally determined empirically [2].

[3], за которое ошибочно принимают предельно критическое давление $$p_2^{крn}$$

под краями винтовой лопасти, соответствующее пятому провально разрушающему фазововому напряженно-деформированному состоянию среды [4].In the proposed method for constructing a pile foundation, its bearing capacity is determined empirically due to the low accuracy of determining the regulatory resistance R of the soil under the blade of the pile and the mismatch of the experimental data with the calculated initial critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

[3], for which the extreme critical pressure is mistaken $${\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000031.png"\; state="\{\{state\}\}">p</figure-callout>}}_2^{\mathrm{to}Rn}$$

under the edges of a helical blade, corresponding to the fifth failure-destroying phase stress-strain state of the medium [4].

и достигают своих пиков в зоне сдвиговых деформаций на ½ радиуса витка сваи, из-за чего рабочая опорная площадь сваи сокращается вдвое.Manually bladed piles can be manually immersed to the ground to a depth of less than 1.5 ... 2.0 m, not exceeding h> s _p / γ _p , when the soil in the array is in tension, and the pile extrusion phenomenon from the base, erroneously explained either by frosty extrusion of the pile from the base, or by swelling of the soil due to high humidity. The diagrams of contact stresses under the straight in the cross section of the pile blades are extremely uneven at the initial (first) critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

and reach their peaks in the zone of shear deformations by ½ of the radius of the pile turn, due to which the working bearing area of the pile is halved.

In order to achieve a uniform pressure distribution under the screw-blade pile foundation and to increase its bearing capacity and double the stability, a new method for constructing a pile foundation is proposed.

, где р_Ф - давление под свайным фундаментом от сооружения, достигается тем, что наконечник свайного фундамента изготавливают с выпуклой полусферической опорной поверхностью винтовой лопасти с углом полуконтакта витков с сжимаемым грунтовым основанием φ_к=φ_н=arcsin[2sinφ_стр/(1+sin²φ_стр)]-φ_стр, где φ_н и φ_стр - углы внутреннего трения грунта нарушенной и ненарушенной структуры, наконечник сваи с винтовой лопастью погружают в массив грунта с дневной поверхности на глубину h≥с_стр/γ_стр, а максимальный диаметр верхнего витка винтовой лопасти сваи принимают обеспечивающей опорную полусферическую площадь контакта с грунтом под давлением $$p_{ср}^{крI}\le \frac{c_{н}\cdot \sin 2{\varphi }_{н}+p_{б}(1+{\sin }^2{\varphi }_{н})}{{\cos }^2{\varphi }_{н}}$$

, где удельное сцепление грунта основания с нарушенной структурой с_н=с_стр[2-tgφ_н/tgφ_стр], с_стр - удельное сцепление структурированного грунта, р_б=(γ_стрh-с_стр)сепφ_стр - гравитационное (бытовое) давление грунта.The technical result according to the method of constructing a pile screw-blade foundation, which consists in conducting engineering surveys of the soil foundation of the foundation of the structure, determines at a depth h of the active compressible thickness the value of φ _pp and with _p - the angle of internal friction and specific adhesion of the soil undisturbed structure, γ _p - specific the weight of the soil, the tip of the pile with the diameter of the screw blade D-varir increasing with its height with a constant step t is screwed into the soil base by rotation and translational immersion and step t is performed one turn into the soil mass to the design depth and further to failure, but as the screw-tip is immersed in the soil, it is expanded with a column of thick-walled pipes joined in height, the pipe string after immersion in the soil of the tip is filled with cement mortar or concrete, the upper end of the pipes close the grillage, while the largest diameter D _{max of the} upper turn of the screw blade is taken to provide a safe first (initial) critical pressure on the ground $$p_{\mathrm{from}R}^{\mathrm{to}RI}>p_F$$

, where p _Ф is the pressure under the pile foundation from the structure, is achieved by the fact that the tip of the pile foundation is made with a convex hemispherical supporting surface of a screw blade with a half-contact angle of coils with a compressible soil base φ _к = φ _н = arcsin [2sinφ _pp / (1 + sin ² φ _page )] - φ _page , where φ _n and φ _page are the angles of internal friction of the soil of a disturbed and undisturbed structure, the tip of a pile with a screw blade is immersed in the soil mass from the day surface to a depth of h≥с _p / γ _p , and the maximum diameter top turn of a screw blade with Wai accept providing support hemispherical contact area with soil under pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}\le \frac{c_n\cdot \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\varphi }_n+p_b(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\varphi }_n)}{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="00000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\varphi }_n}$$

Where specific cohesion foundation soil with broken structure with _n = c _p [2-tgφ _n / tgφ _p] with _p - Specific adhesion structured soil, p _b = (γ _p h-c _p) sepφ _p - gravitational (domestic) soil pressure.

получены на базе развития научного направления «Физики материального контактного взаимодействия» и установления границ пяти фазовых напряженно-деформированных состояний материальной среды, в том числе величины начального критического давления $$p_{ср}^{крI}$$

. При этом установлено, что величина $$p_{ср}^{крI}$$

давления под лопастью сваи становится равномерной при угле контакта полусферических лопастей сваи с грунтом φ_к=φ_н, а несущая способность лопастей сваи повышается на 20% при увеличении вдвое начальной критической устойчивости фундамента. Впервые учитывается явление природного растяжения по вертикали поверхностных слоев грунта на глубину h≤с_стр/γ_стр в массиве поверхностных слоев Земли в условиях гравитационного воздействия, а также установленная закономерность предельного состояния материальной среды с нарушенной структурой, существенно уточняющей закон Ш.Кулона.Hemispherical bearing surface of a screw blade with an angle φ _k = φ _{n of the} half _- contact of the turns with the ground, the depth of immersion of the pile h≥с _p / γ _p and the value of the initial critical pressure safe for the foundation of the pile foundation $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

obtained on the basis of the development of the scientific direction “Physics of material contact interaction” and the establishment of the boundaries of five phase stress-strain states of the material environment, including the initial critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

. It was found that the quantity $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

the pressure under the pile blade becomes uniform at the angle of contact of the hemispherical pile blades with the ground φ _к = φ _н , and the bearing capacity of the pile blades increases by 20% with a doubling of the initial critical stability of the foundation. For the first time takes into account the phenomenon of natural stretch vertically the surface layers of the soil to a depth h≤s _p / γ _p of the array surface of the Earth in a gravitational influence, and the pattern set limit state medium material with broken structure substantially law specifying Sh.Kulona.

A device of a pile screw-blade foundation is known, consisting of a working tip made of a thick-walled pipe with a conical tip, on the side surface of which a screw blade with a constant diameter D-const and a constant pitch t along the height of the tip is welded flat in cross section, the tubular tip is made joined with a column of height-walled thick-walled pipes filled with cement mortar or concrete, and with a grillage at the upper end of the pipe string [1].

зон сдвиговых пластических деформаций грунта из-под ½ площади лопасти сваи за ее края с возможностью потери устойчивости основания и опрокидыванием мелкозавинченного в грунт ствола сваи под нагрузкой.Straight in cross section the blades of the pile foundation work under load as a flat hard stamp with development at a safe first critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

zones of shear plastic deformations of the soil from under ½ the area of the pile blade beyond its edges with the possibility of loss of stability of the base and overturning of the pile shaft finely screwed into the soil under load.

Closest to the proposed device is a pile screw-blade foundation, consisting of a working tip made of a thick-walled pipe with a conical tip, on the lateral surface of which a spiral blade with a constant pitch t of turns of the blade along the height of the shaft of the tip and increasing diameter D-varir is welded screw blades along the height of the tip, the tubular tip is made compatible with the column of height-walled thick-walled pipes poured with cement mortar rum or concrete, and with grillage at the upper end of the pipe string [2, 5].

сваи ввиду развития от краев под ½D диаметра лопасти зон сдвиговых пластических деформаций плотного подстилающего слоя грунта с возможной потерей начальной устойчивости основания и опрокидыванием свайного фундамента.Straight in the cross section of the blades of the screw piles have a low bearing capacity due to the low initial critical ability $$\left(p_{\mathrm{from}R}^{\mathrm{to}RI}=\min \right)$$

piles due to the development from the edges under ½D of the blade diameter of the zones of shear plastic deformations of a dense underlying soil layer with a possible loss of initial stability of the base and capsizing of the pile foundation.

The technical result on the construction of a pile screw-blade foundation, consisting of a tubular metal tip of a pile with an increasing in diameter diameter D-varir screw blades with a constant pitch t, a set of sections of thick-walled pipes joined to the tip, cement mortar or concrete for filling the cavity of joined pipes, grillage is achieved the fact that the screw blades of the working tip are made with a convex hemispherical bearing surface with a half-contact angle of the turns with a compressible soil base φ _к = φ _н = arc sin [2sinφ _p / (1 + sin ² φ _p )] - φ _p , where φ _n and φ _p are the angles of internal friction of the soil of a disturbed and undisturbed structure.

сделать безопасной без развития под лопастью линий сдвиговых (пластических) деформаций. Высокую несущую способность предложенной сваи обеспечивает вся опорная полусферическая поверхность лопастей, в то время как прямые в поперечном сечении лопасти работают на 50%, когда линии сдвиговых деформаций развиваются при давлении $$p_{ср}^{крI}$$

из-под ½ радиуса лопасти сваи. Вдвое повышается и устойчивость основания под сферической поверхностью лопасти сваи.The half-contact angle of the supporting surface of the screw pile blade, equal to the angle of internal friction of the soil of the broken structure under the pile blade φ _k = φ _n , allows the contact stress diagram to be made uniform even at pressure $$p=p_{\mathrm{from}R}^{\mathrm{to}RI}$$

make it safe without the development of shear (plastic) strain lines under the blade. The high bearing capacity of the proposed pile is provided by the entire hemispherical supporting surface of the blades, while straight blades in the cross section work at 50% when shear strain lines develop under pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

from under ½ radius of the pile blade. The stability of the base under the spherical surface of the pile blade is also doubled.

под полусферической в поперечном сечении винтовой лопастью свайного фундамента; на фиг.3 - эпюры контактного начального (первого) критического давления $$p_{ср}^{крI}$$

с центральной зоной (D^max/2) упругих и краевой зоной сдвиговых пластических деформаций под прямой в поперечном сечении винтовой лопастью известного свайного фундамента.The invention is illustrated in graphic materials, where Fig. 1 shows a general view of the construction of a pile screw-blade foundation (single pile) with a helical blade for a working tip of a hemispherical shape; figure 2 is a cross section AA of a pile screw-tip with a plot of the contact initial (first) critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

under a hemispherical cross section of a screw blade of a pile foundation; figure 3 - plot contact initial (first) critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

with a central zone (D ^max / 2) of elastic and an edge zone of shear plastic deformations under a straight in cross section with a helical blade of a known pile foundation.

The pile screw-blade foundation of the structure (Fig. 1) consists of a tubular metal tip 1 piles with increasing in diameter D-varir screw blades 2 with constant pitch t, a set of pipe sections 3, cement mortar or concrete that are joined to the tip (not shown). The screw blade 2 of the working tip 1 is made with a convex hemispherical bearing surface of radius R _sf with a half-contact angle of coils with a compressible soil base φ _к = φ _н = arcsin [2sinφ _p / 1 + sin ² φ _p )] - φ _p , where φ _n and φ _pp - angles of internal friction of the soil of a disturbed and undisturbed structure.

, где удельное сцепление с_н=с_стр[2-tgφ_н/tgφ_стр] грунта с нарушенной структурой, р_б=(γ_стрh-с_стр)ctgφ_{стр -} гравитационное (бытовое) давление. Винтолопастные сваи с отобранным диаметром D_max завинчивают в грунт на проектную глубину h и далее до отказа путем последовательного наращивания наконечником 1 секциями толстостенных полых труб 3. После погружения сваи в грунт внутреннюю полость 4 наконечника 1 и секций труб 3 заливают цементным раствором или бетоном, после установки ростверков свайного фундамента производят обвязку фундамента и возведение сооружения.The construction of a pile screw-blade foundation is as follows. Engineering survey carried subgrade under the foundation structure with the definition of the depth of the active compressible soil strata value φ _p and _p - its angle of internal friction and specific cohesion undisturbed, γ _p - specific weight of the soil. Calculate the depth of immersion of the pile foundation h≥s _p / γ _p and the maximum diameter D _{max of the} upper turn of the screw blade of the pile, providing a support hemispherical area of contact with the soil under the calculated initial (first) critical pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}\le \frac{c_n\cdot \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\varphi }_n+p_b\left(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\varphi }_n\right)}{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="00000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\varphi }_n}$$

, where specific adhesion with _n = s _pg [2-tgφ _n / tgφ _pg ] of soil with a disturbed structure, p _b = (γ _p h-s _pg ) ctgφ _{p is} gravitational (household) pressure. Screw blades with a selected diameter D _{max are} screwed into the soil to the design depth h and then to failure by successively growing the tip 1 with sections of thick-walled hollow pipes 3. After immersing the pile into the soil, the inner cavity 4 of tip 1 and pipe sections 3 are poured with cement mortar or concrete, after Installations of pile foundation grillages make foundation strapping and construction of the structure.

.The proposed method of constructing a pile screw-blade foundation allows to double its stability when the contact stress plots under the hemispherical pile blades become uniform, in contrast to the known straight-sided blades (Fig. 3), where the contact stress peaks occur at ½ of the radius of the turns of the screw blade and it is possible to tilt the trunk piles to one side when pressure is exceeded over $$p_{\mathrm{from}R}^{\mathrm{to}RI}$$

.

, удельное сцепление $$c_{стр}^{сг}=0,2кг/с{м}^2$$

, угол внутреннего трения $${\varphi }_{стр}^{сг}={25}^o$$

, для торфа - $${\gamma }_{стр}^{Т}=0,0013кг/с{м}^3$$

, $$c_{стр}^{Т}=0,15кг/с{м}^2$$

, $${\varphi }_{стр}^{Т}={32}^o$$

.An example implementation of the method. Peat, drained from the surface, lies to a depth of 1.0 m and is lined with loam up to 3 m, specific gravity of loam $${\gamma }_{\mathrm{from}tR}^{\mathrm{from}g}=0,0019\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="3"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^3$$

specific grip $$c_{\mathrm{from}tR}^{\mathrm{from}g}=0,2\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$$

angle of internal friction $${\varphi }_{\mathrm{from}tR}^{\mathrm{from}g}={25}^o$$

for peat - $${\gamma }_{\mathrm{from}tR}^T=0,0013\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="3"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^3$$

, $$c_{\mathrm{from}tR}^T=0,\mathrm{fifteen}\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$$

, $${\varphi }_{\mathrm{from}tR}^T={32}^o$$

.

. Таким образом наконечник сваи следует завинчивать на глубину 1,0 м, проходя слой торфа, и далее до отказа в суглинок, например, на 2,0 м от поверхности основания. На глубине h=2,0 м бытовое давление составляет величинуDesign depth of insertion of a propeller blade $$h\ge c_{\mathrm{from}tR}^T/{\gamma }_{\mathrm{from}tR}^T=0,\mathrm{fifteen}/0,0013=115,38\mathrm{from}m$$

. Thus, the tip of the pile should be screwed to a depth of 1.0 m, passing a layer of peat, and then to failure in the loam, for example, 2.0 m from the surface of the base. At a depth of h = 2.0 m, household pressure is

. Начальное (первое) критическое давление суглинка $$p_{ср}^{крI}=\frac{c_{н}\cdot \sin 2{\varphi }_{н}+p_{б}\left(1+{\sin }^2{\varphi }_{н}\right)}{{\cos }^2{\varphi }_{н}}=\frac{0,2369\cdot \sin 41,6392+0,3326\left(1+{\sin }^{2}20,8196\right)}{{\cos }^{2}20,8196}=0,6089кг/с{м}^2$$

, где $$\begin{array}{l}{\varphi }_{н}^{сг}=\arcsin \left[2\sin {\varphi }_{стр}/\left(1+{\sin }^2{\varphi }_{стр}\right)\right]-{\varphi }_{стр}=\\ =\arcsin \left[2\sin {25}^o/\left(1+{\sin }^2{25}^o\right)\right]-{25}^o=45{,}^{o}8196-{25}^o=20{,}^{o}8196\end{array}$$

, $$p_b=\frac{{\gamma }_T{h}_T-c_{\mathrm{from}tR}^T}{tg{\varphi }_{\mathrm{from}tR}^T}+\frac{{\gamma }^{\mathrm{from}g}{h}^{\mathrm{from}g}-c_{\mathrm{from}tR}^{\mathrm{from}g}}{tg{\varphi }_{\mathrm{from}tR}^{\mathrm{from}t}}=\frac{0,0013\cdot \mathrm{one\; hundred}-0,\mathrm{fifteen}}{tg{32}^o}+\frac{0,0019\cdot 200-0,2}{tg{25}^o}-\frac{0,0019\cdot \mathrm{one\; hundred}-0,2}{tg{25}^o}=0,3326\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$$

. The initial (first) critical pressure of loam $$p_{\mathrm{from}R}^{\mathrm{to}RI}=\frac{c_n\cdot \mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\varphi }_n+p_b\left(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\varphi }_n\right)}{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="00000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\varphi }_n}=\frac{0,2369\cdot \sin 41,6392+0,3326\left(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{twenty},8196\right)}{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="00000031.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{twenty},8196}=0,6089\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$$

where $$\begin{array}{l}{\varphi }_n^{\mathrm{from}g}=\arcsin \left[2\sin {\varphi }_{\mathrm{from}tR}/\left(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\varphi }_{\mathrm{from}tR}\right)\right]-{\varphi }_{\mathrm{from}tR}=\\ =\arcsin \left[2\sin {25}^o/\left(\mathrm{one}+{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="00000031.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{25}^o\right)\right]-{25}^o=45{,}^{o}8196-{25}^o=\mathrm{twenty}{,}^{o}8196\end{array}$$

,

. $$c_n^{\mathrm{from}g}=c_{\mathrm{from}tR}^{\mathrm{from}g}\left[2-tg{\varphi }_n^{\mathrm{from}g}/tg{\varphi }_{\mathrm{from}tR}^{\mathrm{from}g}\right]=0,2\left[2-tg\mathrm{twenty}{,}^{o}8196/tg{25}^o\right]=0,2369\mathrm{to}g/\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000031.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$$

.

. Зная вес N=7749 кг сооружения, легко определить необходимое минимальное количество свай n_min=N/P=7749/30=18 шт. Применение полусферической поверхности лопастей свай: при D_max=30 см площадь ее опорной поверхности F_сф=2πR_сфh_c=2π42,2·2,75=729,2 см,When vintolopastnoy pile diameter D _max = 30 cm square flat bearing surface F _mp = πD ^2/4 = 706.86 cm ^2, and the permissible load on the pile is $$P_{Pl}=p_{\mathrm{from}R}^{\mathrm{to}RI}\cdot F_{Pl}=0,6089\cdot 706,86=430\mathrm{to}g$$

. Knowing the weight N = 7749 kg of the structure, it is easy to determine the required minimum number of piles n _min = N / P = 7749/30 = 18 pcs. The use of the hemispherical surface of the pile blades: at D _max = 30 cm, the area of its supporting surface F _sf = 2πR _sf h _c = 2π42.2 · 2.75 = 729.2 cm,

where R _sf = (D _max / 2) sinφ _n = (30/2) sin20, ° 8196 = 42.2 cm;

. Несущая способность полусферической сваи повысилась на 3,15%, количество свай требуется 18 шт, однако устойчивость свайного фундамента увеличилась вдвое.h _c = R _sf - (D _max / 2) / tg20, ° 8196 = 42.2-39.45 = 2.75 cm - segment height, and the permissible load on the pile is $$P_{\mathrm{from}f}=p_{\mathrm{from}R}^{\mathrm{to}RI}\cdot F_{\mathrm{from}f}=0,6089\cdot 729,2=444\mathrm{to}g$$

. The bearing capacity of a hemispherical pile increased by 3.15%, the number of piles required 18 pieces, but the stability of the pile foundation doubled.

Hemispherical screw blades of a new design should be manufactured and selected according to a given diameter D _max and a given angle ≈φ _{n of the} internal friction of the soil with a disturbed structure.

Information sources

1. Metelyuk N.S., Shishko G.F., Solovieva A.B., Gruzintsev V.V. Piles and pile foundations. - Kiev, Budivelnik, 1977. - P.29-30.

2. Zhelezkov V.N. Screw piles in energy and other fields of construction - St. Petersburg: Publishing House: house "PRAGMA", 2004 - 128 p.

3. Ter-Martirosyan Z. G. Mechanics of soils / Textbook - M .: Publishing house of the Association of construction universities, 2005. - S.391-392.

4. Khrustalev E.N. Contact interaction in geomechanics. Part I: Bearing capacity of the foundations of structures. - Tver, TSTU, The Golden Letter, 2004. - P.78, 80.

5. RF patent for utility model No. 93412 "Screw pile".

Claims (2)

1. The method of constructing a pile screw-blade foundation, which consists in carrying out engineering surveys of the soil foundation of the foundation of the structure, determine at a depth h of the active compressible thickness the value of φ _pp and with _p - the angle of internal friction and the specific adhesion of the soil undisturbed structure, γ _p - specific gravity of soil, the pile tip with a screw blade diameter D-varir increasing with its height with a constant step t is screwed into the soil base by rotation and progressive immersion by step t for one revolution in mass after sinking the soil to the design depth and further to failure, as the screw-tip is immersed in the soil, it is expanded with a column of thick-walled pipes joined in height, the pipe string after immersion in the tip soil is filled with cement mortar or concrete, the upper end of the pipes is covered with grill, with the largest diameter D _{max of the} upper turn of the helical blade is taken to provide a safe first (initial) critical pressure on the ground $$p_{\mathrm{from}R}^{\mathrm{to}RI}>p_F$$

Where p _F - under pressure from the pile foundation structure, characterized in that the tip of the pile foundation vintolopastnogo manufactured with a convex hemispherical support surface with the angle of the screw blade turns to semicontact compressible ground base _to φ _n = φ = arcsin [2sinφ _p / (1+ sin ² φ _p)] - φ _p, φ _n, and where φ _p - internal friction angles soil disturbed and undisturbed, the pile tip with the screw blade was immersed in an array of soil from the surface to a depth h≥c _p / γ _pp, and the maximum diameter of the upper turn in ntovoy blade providing support piles take hemispherical area of contact with the ground under pressure $$p_{\mathrm{from}R}^{\mathrm{to}RI}\le \frac{c_n\cdot \sin 2{\varphi }_n+p_b\left(\mathrm{one}+{\sin }^2{\varphi }_n\right)}{{\cos }^2{\varphi }_n}$$

Where specific cohesion foundation soil with broken structure c _n = c _p [2-tgφ _n / tgφ _p], c _p - specific cohesion structured soil, p _b = (γ _p hc _p) ctgφ _p - gravitational (domestic) soil pressure . 2. A device of a pile screw-blade foundation, consisting of a tubular metal tip of a pile with a screw blade diameter D-varir increasing in height with a constant step t, a set of sections of thick-walled pipes, cement mortar or concrete joined to the tip for filling the cavity of joined pipes, grillage, characterized in that the screw blade of the tip is formed with a convex hemispherical support surface with an angle semicontact turns with compressible ground base _to φ _n = φ = arcsin [2sinφ _p / (1 + sin ² φ _p)] - φ _str , where φ _n and φ _str are the angles of internal friction of the soil of a disturbed and undisturbed structure.

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