Foundation with projections by foot portion

FIELD: construction.

SUBSTANCE: invention relates to the field of construction, namely for the structure of free-standing foundations, erected on natural basis during construction of buildings and constructions for various purpose. Foundation under the column includes the column footing, slab part. In order to increase the carrying capacity and reduce the draft at the foot portion of foundation, protrusions are made at an angle of 120°, at that, the area of protrusions Aprotr is of (0.60-0.90) from the total area of the foot portion A. In the central portion of the foot portion of foundation there is a recess filled with rigid material with height h, not exceeding the value of the maximum permissible draft Su for this type of construction.

EFFECT: technical result consists in the increase of load-bearing capacity to the action of vertical and horizontal loads, reduction of foundation draft.

10 dwg

 

The invention relates to the field of construction, namely for the device detached foundations, erected on a natural basis in the construction of buildings and structures for various purposes.

Known design detached Foundation, which is arranged under the columns and pillars of frame buildings (B.A. Yagupov "of the Building structure. Bases and foundations". - M.: stroiizdat, S).

Closest to the invention analog is the base design for the column, including Podolinec, which is joined with the column, and plate part that transmits the load to the ground (V. Veselov, "Design bases and foundations". - M.: stroiizdat, 1990, p.134).

The disadvantages of these structures foundations is low bearing capacity and high intensity.

The technical result consists in increasing the load bearing on the action of vertical and horizontal loads and reduce settling of the Foundation.

The technical result is achieved by the fact that in the sole Foundation made the tabs at an angle of 120°, and the area of the protrusions Andinvoiceis (0,60-0,90) of the total area of the sole And, in the Central part of the sole is placed holes filled with hard material, the height h of not exceeding the maximum allowable precipitation Sufor dinogetia structures.

The invention is illustrated by drawings:

figure 1 shows the base with the tabs on the sole in the plan;

figure 2 shows a section of the basement 1-1;

figure 3 shows a fragment of experimental research Foundation with the protrusions;

nafig shows the results of die testing of foundations in the field;

figure 5 - calculated scheme of the finite element method of a base with protrusions;

figure 6 shows graphs of precipitation from the load S=f(p) for the Foundation of a square shape and a base with protrusions;

7 shows a graph of Foundation settlement with the tabs from the ratio of the area of the projections to the square foot basement Andinvoice/A;

on Fig shows contours of vertical displacement Uysoil at a depth of 1.0 m from the base of the square Foundation and basement with ledges;

figure 9 shows the vertical displacement Uyat the base of a square Foundation and basement with tabs (vertical incision);

figure 10 shows the distribution areas of the plastic deformation at the base of the square of the Foundation and Foundation with the tabs.

Detached Foundation 1 on the natural basis for the column contains the tabs 2, performed at an angle of 120°. In the Central part of the sole 3 is posted recess 4 is filled with a rigid material. After the boiler is Ana and leveling base 5 is arranged a recess 4 with hard material as part of the Foundation. Then top set the design of the base 1 with the ribs 6 on the outer elements of the protrusions 2 Foundation structure.

In the area of the cut between the adjacent faces of the projections 2 of the Foundation created the arch effect 7 in the soil, which leads to an increase in bearing capacity due to the involvement of a larger volume of soil at the base.

Values of bending moments along the sole of the Foundation can be reduced by transforming the plot of the contact pressure. The nature of the plot of the contact stresses can be changed by placing the recess in the Central part of the soles filled with a rigid material.

At the initial moment load acting on the Foundation with the tabs, transmitted to the ground via holes filled with a hard material, in the area of lesser width of the sole. As load increases on the Foundation pressure on the base is evenly distributed across the entire width of the sole Foundation. Thus, the presence of cavities filled with a rigid material, transforms a plot of the contact pressure on the sole, leads to their concentration in the Central part of the sole of the Foundation.

The height of the recess in the center of the sole of the Foundation should be h≤Suwhere Su- the maximum permissible draught for this type of structures regulated by the norms and component with the responsible S u=(10÷15) see When uploading Foundation with projections based on a joint work with the basis of settlement of Foundation S should not exceed the values of Sui.e. must satisfy the condition S≤Su.

Experimental study of bearing capacity, settlement of Foundation with the tabs were conducted in field conditions (figure 3). Field studies were carried out with the bases the same area of the sole (A=5000 cm2in accordance with GOST 20276-99 Soils methods of determining strength and deformability". Level of stress was reported by a hydraulic Jack DG-50, check the size of the load was carried out using the exemplary gauge 40 MPa intercept Tampa. Observation of the movements of the foundations was carried out on three indicators ICH-50 to conditional stabilization, not exceeding 0.1 mm precipitation in the last hour of observation.

The Foundation is overlain by Quaternary alluvial-deluvial sediments are represented by sand medium size, medium density with e=0,59; γ=18,5 kN/m3; φ=32°; C=kPa; F=29,2 MPa. The experimental results shown in figure 4. When the load P=CN (σ=kA) sludge Foundation with the tabs 1.67 times less rainfall square Foundation, equal the square foot (A=5000 m2).

The study of stress-strain state on the establishment of the Foundation with the protrusions on the sole is produced by the method of finite elements in elastic-plastic formulation (figure 5). The task was solved using complex geotechnical PLAXIS in the spatial setting. The prediction residue and the bearing capacity of the Foundation is made with regard to the formation of zones of limiting equilibrium in the active area of the base by tabs. In the calculations, graphs of the dependence of precipitation on load S=f(p) (6) for a square Foundation and basement with protrusions on the sole (cohesive soil). The calculations showed that the dependence of S=f(P) are nonlinear. Carrying ability of the base with the tabs in 1,136 times more load bearing capacity of square footings.

The influence of the ratio of the area of the protrusions Andinvoice/A in the base with the tabs in the bottom sediments and the bearing capacity of the Foundation (7). The biggest reduction of Foundation settlement with the tabs is achieved when (ainvoice/A=(0,60-0,90).

Built contours of vertical and horizontal movements, vertical, horizontal and tangential stresses, zones of plastic deformation at the base of the square of the Foundation and Foundation with the tabs.

Analysis of the distribution of vertical displacement of the soil at the base at a depth of 1.0 m from the sole Foundation shows that the width of the deformation zone in the active zone of the base with the tabs in 1.2 times greater than for a square Foundation (Fig.

It is established that the contours of vertical displacements at the base of the square of the Foundation and Foundation with the protrusions are elongated along the vertical axis (Fig.9). The highest values of vertical displacements are located in the area adjacent to the sole Foundation. With depth faster fade layer-by-layer movement for the Foundation with the tabs, the width of the deformation zone 20-30% more than the square of the Foundation. Thus, in the base with the tabs, the work included a larger volume of soil, this leads to an increase bearing capacity and reduce sediment in comparison with a square base.

Changing the shape of the sole of the foundations affects the formation and development of plastic deformations zones in the active zone (figure 10). Zone of plastic deformations arise in the area adjacent to the sole at P=0.05 MPa with increase of the load on the Foundation developed in the sides and bottom.

The use of the invention allows to increase the load bearing capacity of vertical and horizontal load, to reduce settling of the Foundation, to reduce the consumption of Foundation construction.

The Foundation for the column, including Podkolodny, plate, portion, characterized in that to increase bearing capacity and reduce sediment in the bottom of the Foundation made the tabs at an angle of 120°, and the area of the protrusions is invoiceis (0,60-0,90) of the total area of the sole And, in the Central part of the sole Foundation hosted a recess filled with a rigid material, the height h of not exceeding the maximum allowable precipitation Sufor this type of structures.



 

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