RU2708929C1 - Reinforcement method of foundation base during reconstruction of buildings and structures - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction and can be used for reinforcement of foundations of barrel-type foundations and shell-type foundations during reconstruction of buildings and structures subjected to uneven precipitation and loads arising from their local soaking and freezing during operation. Method of reinforcing a foundation base during reconstruction of buildings and structures involves placing reinforcing elements parallel to each other in the base with formation of their end sections outside the outline of the foundation. First, leading wells are made at an angle to foundation, reinforcing elements are made by punching of semi-dry compacting sand-cement mix by means of pneumatic puncheon at its multiple driving to the leader well. Then, formation of reinforcement elements is installed under the sole of the cement-sand mixture base into the wells and cement-sand mortar is poured into the wells. Then reinforcement grid is laid in points of armoelements output, they are welded together and poured with concrete.

EFFECT: technical result consists in simplification of technology, increase of bearing capacity of foundation in flooded ground conditions, prevention of deformations of base and foundation, as there are no precipitations and effects of forces of frost heaving soil with simultaneous reduction of labor intensity and metal consumption.

3 cl, 2 dwg

Description

The invention relates to construction and can be used to strengthen the foundations of strip foundations and glass-type foundations during the reconstruction of buildings and structures that underwent uneven precipitation and stresses during operation due to their local soaking and freezing.

There is a method of fixing the foundation foundation (see USSR author's certificate No. 1671778, class E02D 27/08, 1988), according to which trenches are dug along the structure to be strengthened, then wells are laid in the base with a pneumatic punch, bent like design lines of equal horizontal stresses that fill cement mortar and connect at the ends with jumpers. The distance from the bottom point of the foundation to the top point of the axis of the curved pile should be no more than three diameters of the pile, and the distance between the axes of two parallel piles should be at least six diameters. The junction of piles with jumpers is made with reinforcing elements.

The disadvantage of this method is the limited application. For example, it cannot be used in soils where the walls of paved wells are being washed or shed.

Closest to the present invention in its essence and the achieved effect is a method of reinforcing the foundation foundation during the reconstruction of buildings and structures, including the development of a trench on the outside of the foundation and placement of horizontal reinforcing elements parallel to each other from the trench with the formation of their end sections outside the foundation outline , the placement of the elements is carried out using a pneumatic punch close to the bottom of the foundation with a step equal to 3 heights of the section of the element, and the height of the cross section of the arm is within 0.125-0.075 of the width of the foundation, and the end sections form within 0.5-1.5 of the width of the foundation (see RF patent No. 2032024, class E02D 27/08; E02D 37/00, publ. 27.03 .1995).

The disadvantage of this method, adopted as a prototype, is the large labor and material costs, as it requires excavation of the soil at the base, as well as the use of metal pipes. In addition, this method does not have sufficient reliability in weak water-saturated soils. In such soil conditions, reinforcing elements having a sufficiently large weight will be deposited in the flooded soil base, which will inevitably lead to a decrease in the bearing capacity of the foundations. In heaving ground conditions, an increase in the area of bearing on the ground will increase the impact on the foundation of frost heaving forces and, as a result, an increase in deformations in the building.

The technical task is to increase the efficiency of strengthening the base of the foundation.

The specified technical problem is achieved by the fact that in the method of reinforcing the foundation foundation during the reconstruction of buildings and structures, including placing reinforcing elements parallel to each other in the base with the formation of their end sections outside the foundation contour, leader wells are initially performed at an angle to the foundation, reinforcing elements are performed by injection of a tamping semi-dry cement-sand mixture with a pneumatic punch during its repeated penetration into the leader well, then after the image Bani a foundation base broadening of the cement-sand mixture into the wells and set armoelementy poured cement-sand mortar, and in the output stack locations armoelementov reinforcing mesh, combined them by welding and poured concrete. As a reinforcing element, reinforcement with a diameter of 12 ÷ 18 mm is used. As a tamping mixture, a semi-dry cement-sand mortar mixture with a composition of 1: 2 ÷ 1: 3 by volume at a water-cement ratio W / C = 0.26 ÷ 0.32 is used.

In FIG. 1 shows a diagram (cross section) of the arrangement of reinforcing the foundation foundation; in FIG. 2 is a view along AA in FIG. 1.

The method is as follows.

In the soil mass under the foundation 1 with column 2, a pneumatic punch is drilled to the design elevation to the inclined leader well 3 at an angle of not more than 45 ° to the day surface. After reversing and exiting the pneumatic punch to the surface, reinforcing elements are performed by filling the well 3 with a semi-dry cement-sand mixture and restarting the pneumatic punch into the well. During the sinking period, the cement-sand mixture is rammed into the bottom of the borehole 3 and partially into its walls due to the impact, forming a broadening 4 from the ramming semi-dry cement-sand mixture and compacted soil shell 5. Depending on the soil moisture and its deformation modulus, additional penetrations are carried out 3 to 5 times. At the end of the broadening 4 formation, an reinforcing element 6 is installed in each well 3 and the cast cement-sand mortar 7 is poured, which is a semi-dry cement-sand mortar with a composition of 1: 2 ÷ 1: 3 by volume at a water-cement ratio W / C = 0.26 ÷ 0.32. Upon completion of the manufacture of all piles, a small excavation is made in the places where the reinforcing elements 6 exit, the reinforcing mesh 8 is laid, combined by welding with the reinforcing elements 6, and poured with concrete 9.

The reinforced soil layer works as follows.

The load from the foundation 1 is transferred to the reinforcing elements, which together with the sealing zone 5 act on the base, as a result of which the pressure from the structure is distributed over a large area, which leads to a decrease in the foundation sediment.

The proposed method of reinforcing the foundation foundation is most appropriate for hardening the foundation soils and strengthening the glass type foundations and strip foundations of shallow laying in the conditions of their irrigation.

The necessity of reinforcing the foundation foundation is determined both by visual inspection and control of the formation and opening of cracks and deformations in the building, and based on the calculation of the bearing capacity of the foundation foundation soils after engineering and geological surveys.

Determination of the design resistance of the soil of the foundation of the strip foundation with the possibility of soaking them.

For a building whose length is L = 36 m, height H = 6 m, the width of the foundation of the outer walls b = 0.8 m, the depth of the foundation from the level of planning d = 3.0 m; basement depth d _b = 2.6 m, soil resistance was determined by the formula SNiP 2.02.01-83 Foundations of buildings and structures:

where R is the desired calculated soil resistance of the base in the flooded state;

γ _c1 = 1.1 is the coefficient of working conditions, taken as for water-saturated soils (J _α >0.5);

γ _c2 = 1.0 - also taken as for the same soils with the ratio of the length of the building to its height L / H = 6);

k is a coefficient taken equal to 1 if the strength characteristics of the soil (C and ϕ) are determined by direct tests;

M _γ = 0.32; M _g = 2.3; M _s = 4.84 - coefficients taken depending on the value of the angle of internal friction ϕ _II = 15 ^° ;

k _z = 1,0 - coefficient taken with the width of the foundation b <1,0 m;

b = 0.8 m - the width of the foundation of the outer walls;

γ _I = 10 kN / m ³ - the value of the specific gravity of the soil lying below the bottom of the foundation, taking into account the weighing effect of water at full watering;

γ _II ^' = 17 kN / m ³ - the same soil lying above the bottom of the foundation;

d _{1 - the} depth of the foundation from the basement floor;

h _s is the thickness of the soil layer above the base of the foundation from the basement side, m;

h _cf = 0.1 m - the thickness of the basement floor structure, m;

γ _cf = 2.3 kN / m ³ is the calculated value of the specific gravity of the basement floor structure, kN / m (tf / m);

h _s = dd _b -γ _cf = 3.0 m - 2.6 m - 0.1 m = 0.3 m.

C _II = 6 kPa - the calculated value of the specific adhesion of the soil, lying directly under the base of the foundation.

Substituting these values in the calculation formula, we obtain:

R = 1.1 * 1.0: 1.0 * (0.32 * 1.0 * 0.8 * 10 + 2.3 * 17 * 0.435 + (2.3-1.0) * 2.0 * 17 + 4.86 * 6] = 102.1 kPa.

Comparing the obtained value with the calculated soil value adopted in the project (2.5 kgf / cm ² , i.e. 250 kPa), we establish that the calculated soil resistance of the base of the strip foundation when soaking becomes almost 2.5 times lower than the required value, which indicates that the design of the building was carried out without taking into account the possible soaking of the soil of the base, and for the safe operation of the building requires strengthening of the proposed method.

The introduction of cement-sand mixture into flooded soils significantly increases the value of the deformation modulus in the most stressed (upper) part of the core core under the base of the foundation.

When the wells are drilled with a pneumatic punch, the soil is not removed from the well, but is rammed in the radial direction from the axis into the walls of the well 3. In this case, the soil is compacted around the well 3, a compacted soil shell is formed 5. The application of compaction zones during each subsequent well penetration allows creating a concrete screen, preventing moisture migration to the freezing front. This circumstance ensures the elimination of the forces of frost heaving and increases the stability of the foundations of the building.

Using the proposed method of reinforcing the foundations foundation allows you to restore the physico-mechanical characteristics of the foundations soils, as the tamping semi-dry cement-sand mixture absorbs moisture during its hardening. At the same time, the bearing capacity of the foundation increases, since the load is transferred from the existing foundation to the bearing soil-concrete pile wall, anchored on top at the level of the day surface in concrete 9. This ensures the development of the supporting area of the foundations and, thus, the reduction of the foundation pressure on the soil.

The technical result of the proposed method for strengthening the basement of the foundation compared to the prototype consists in simplifying the technology, increasing the bearing capacity of the foundation in flooded soil conditions, preventing deformation of the base and foundation, since precipitation and the effects of frost heaving are eliminated while reducing labor intensity and metal consumption.

Claims (3)

1. A method of reinforcing the foundation foundation during the reconstruction of buildings and structures, including placing reinforcing elements parallel to each other at the base with the formation of their end sections outside the foundation contour, characterized in that the leader wells are initially made at an angle to the foundation, reinforcing elements are performed by pumping the tamping semi-dry cement-sand mixture with a pneumatic punch during repeated penetration into the leader well, then after the foundation is formed under the sole broadening of the cement-sand mixture into the wells and set armoelementy poured cement-sand mortar, then armoelementov output locations are placed a mesh, combined them by welding and poured concrete. 2. The method of reinforcing the foundation foundation during the reconstruction of buildings and structures according to claim 1, characterized in that reinforcement with a diameter of 18-20 mm is used as reinforcing elements. 3. The method of reinforcing the foundation foundation during the reconstruction of buildings and structures according to claim 1, characterized in that a semi-dry cement-sand mortar mixture of 1: 2 ÷ 1: 3 in volume with a water-cement ratio of 0.26 ÷ 0 is used as a tamping mixture , 32.

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