SU1680876A1 - Foundation for building on swelling ground - Google Patents

Abstract

The invention relates to the erection of building foundations on swelling soils and provides an increase in the reliability of the foundation. The foundation contains foundation block 1 and slab 2 placed on cushion 3 of loose non-dull material with structural strength that meets the condition: b gr. where Pbw is the swelling pressure of the natural soil; .tr - structural strength of the soil cushion; - design compressive stress in the pad. The pillow can be made of sand, reinforced with cement in the amount of 2-6 wt.%, 1 hp f-crystals, 4 sludge. ////// A (L SZ - “g Ooo oo oo vj ze

Description

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The invention relates to the construction, in particular to the construction of building foundations on swelling soils,

The purpose of the invention is to improve the reliability of the foundation,

Fig. 1 shows a foundation, a cross-section) in Fig. 2 — the diagrams of the vertical compressive stresses in the Pillow and the structural strength of the soil of the pillow in FIG. 3 are the foundation for swelling of the soil under the pillow; Cross-section in FIG. - Pressure diagrams from compressive stresses and swelling and structural strength.

The foundation consists of a foundation 1 and a slab 2 mounted on a Compensation cushion 3, which is poured on the swelling soil of base k. The cushion is made of loose, loose, unstuffed, unprinted Nrunth, which has structural strength. In the cushion there are stresses transmitted by the foundation and stresses from swelling. The structural strength of the soil is polush, tp due to the layering of the pads, the pillow varies with stepwise depth. Stresses decrease with depth. Similarly, C structural strength, tp. Loose sand reinforced with cement in the amount of 2-6% by weight can be used as a pillow material.

The foundation works as follows.

Under the influence of operational loads, the voltage is bp, tp over the entire thickness of the cushion. vrmm ground singing practically does not occur. When the base is wetted, a rise in the soil surface occurs due to its swelling. The rise is most often uneven due to the heterogeneity of the soil and the unevenness of its moisture. In the places of the swelling of the base In the cushion, the compressive stresses age Pc, w. In the lower part of the cushion, where the structural strength of the soil is less, the ground is 5 in which the ap + r links are destroyed, the ground begins to be compacted, compensating for the lifting of the base from the nichi and preventing deformation of the building. P during the swelling of the zone upl Hi Hi i nn p flare upwards up to r, it is about, and scoops

764

energy swell. After that, deformations of the cushion cease.

The values of structural strength are set by the variables: in the upper part of the gps (1,2 - 1, in the lower part - 5yrR (1.1 - 1.3) bgr.

The height of the pillow hr is determined from the condition:

hn QH / Ј

where Ln is the maximum possible rise of the surface of the swelling soil,

g-g- - relative deformation of the cushion under pressure under the base of the foundation (1.1-1.2). Experiments conducted on fine sand with a porosity coefficient of. 0.9-0.95, showed that the introduction of 2-8g of cement by weight provides bstr 120-390 kPa (see table).

Example. Separate foundations with the size of 2–2 m are designed for the building. Pressure under the sole is P 180 kPa. From operating experience of similar structures, it is known that the rise of the base folded by swellable clay soil can reach 9 cm. The compensating pad is made of fine sand with a porosity ratio of 0.90 - 0.95, the structural strength of which is reinforced with cement is shown in the table. At a pressure of 198-216 kPa (10–20% more than 2p), the deformation of the pillow is Ј h 0.060. Find t pillow height:

, 65 15 ° cm

Take a pillow of three layers

0.5 m

The average pressure in the upper layer, taking into account the dead weight of the cushion soil, is b 179 kPa. The required value of structural strength

 (1.2-1.4) 215-251 kPa.

The ho table finds that it is necessary to introduce cement in the amount of%. In the bottom layer: & $ 126 kPa, (1.1-1.3) -126 139-16 kPa. Interpoling the experimental data, it is found that 2.5% of cement is required to be entered. In the middle layer of b% of cement

Claims (2)

1. The foundation of the building on the swelling soils, including the foundation block and the slab, is installedDosign- (GettrWal deformation under pressure j j cement || b gr (0,8-0,9) b sgr | fTZp (1, 1-1, 2) So; mass nl cushion of loose non-teddy ground, characterized in that, in order to increase the reliability of the foundation, the cushion is made of material whose structural strength meets the condition  Јzp, where Pc is the pressure of swelling of the natural soil  structural strength of the pillow material  - calculated compressive stress in the cushion. 2. The foundation of claim 1, about tl and h-th id and so that the pillow is made of sand, reinforced with cement in an amount of 2-6 wt.%. & 2p p ( / Sharp page FIG. 2 Rlg Fig.Z Psw + 6 zp v ° cmp a: -c Fiyo.1 +