SU1305255A1 - Method of constructing pile foundation - Google Patents

Abstract

The invention relates to the field of construction, and in particular to methods for erecting pile foundations in subsidence loess type II soils (if possible, a drawdown from its own weight). The aim of the invention is to reduce the labor intensity of the work and accelerate the construction of the foundation. The method is carried out as follows. A pit is dug in the ground, and along its contour a slot 9 is formed with a depth of 0.8-1.0 of the depth of the subsidence of the soil, which is filled with a low-filtration material. Then, borehole 6 is drilled to a depth starting from which the relative subsidence is less than 0.015-0.03. The wells are filled with drainage material 7 to a level exceeding the level at which the relative subsidence is 0.01 by the value of h Ztg / 3, where E is the distance between wells; - angle of water spreading to the side of the well. Piles are erected after termination of soaking the soil and lowering its moisture content to a value of at least 1.2Wp, where WP is the soil moisture content on sec (L: W Шх: - Fig. 2

Description

1305255 border rolling. At the same time, the sheet is up to density in a dry state.

the maximum distance between the heels is prescribed taking into account the soil compaction. The invention relates to construction, and specifically to methods of erecting pile foundations in subsiding loess soils of type II (if it is possible to draw down the soil from its own weight).

The purpose of the invention is to reduce the labor intensity of production-work and accelerate the construction of the foundation.

Figure 1 shows graphs of changes in the relative subsidence of 56 ° depth Nd of the subsidence, changes in depth Hg of the density of the PJ-subsidence arm in the bony state, respectively, in natural occurrence, with the total elimination of subsidence from its own weight after compaction by pre-soaking and after driving the pile in FIG. 2, the location of the drainage wells filled with drainage material in the lower part of the driftline, the spreading edge of the water, as well as the wetted area from

wells, cut.

The method is carried out as follows.

At the beginning of the graph of the change in depth Hgg of the relative subsidence Sggj obtained on the basis of engineering geological surveys, the depth at which, 015- -0.03, is determined within the limits of the subsidence sequence Hgg. This depth determines the depth of drainage wells h. The values of 0.015-0.03 are determined from the experience of compaction of subsidence soils by soaking taking into account the different water permeability of soils: fgg values 0.03; 0.02; 0,015. Attributed to sandy loam, loam and clay, i.e. the higher the permeability, the greater the gg and the smaller the depth of the wells h. If the drainage wells do not reach the depth h, at which, 015-0.03, it is not ensured fast enough.

equal to 1.5-1.65 t / m. 1 hp f-ly, 2 ill.

five

five

 ,, g

uniform soil moistening and elimination of their drawdown properties. With a well depth greater than hj., Water consumption and the cost of base preparation work increase.

Then, according to schedule 1, the depth hv., At which 0.0, i.e. the depth from which the ground begins to draw down due to its own weight (at this depth, the pressure due to the own weight of the soil is equal to the initial subsidence pressure). Graphs 2 and 3 (Fig. 1) are constructed, characterizing the change in depth Hgg of the density PJ of the dry soil in natural occurrence and the minimum allowable density p at which there is no subsidence of the soil due to its own weight.

At the next stages, the foundation pit is dug and the drainage wells 6 are drilled with a depth of h :, which, as the pre-soaking experience has shown, it is most expedient to pass through a diameter of 20-40 cm, having them 3-8 m in plan.

Drainage wells are poured into drains, - with a growing material 7 (medium, coarse, gravelly sand, gravel, sand-gravel, fine gravel, etc.) to a level h-h higher than the level at which relative subsidence & the value, where i is the distance between the wells, p is the angle of water spreading to the side of the well, which is assumed to be equal to sandy deposits / 3 35, and loams and clays are 5 55. When filling the drainage wells to a height exceeding the level where ic, e 0.01, by the amount, the side contours of the humid zones (during the soaking of the drawdown mass) are closed off from the neighboring wells at the depth from which the subsidence begins.

313

After the passages, the excavation pit and the drainage wells are arranged along the contour. A narrow slot 8 is drilled with a depth equal to 0.8-1.0 of the depth of the reservoir, and is filled with a little filtering material (for example, mud). The slot is arranged in order to reduce the flow rate of the water, the zones 9 of its spreading to the sides by drilling of well-located wells, immersing the cutting knife (not shown), washing out the high-pressure jet.

Example. Carry out the method

Then soil is soaked.

„- erection of pile foundation with

water supply through wells in those

construction of a 16-story brick

20

0.5-1.5 months until a subsidence of soil in a subsidence is shown with a relative subsidence, 0. After the soaking is stopped, the soil within the humid zone is held 5–10 days to level and reduce its moisture content to 1.2Wp, where Wp is the moisture at the rolling edge to ensure effective soil consolidation during subsequent pile installation (not shown).

During this period, the change in the depth Hgg of the soil density Oj is determined in a dry state after pre-soaking (Figure 4).

Next, proceed to the construction of driven or packed piles in punched wells. In this case, the maximum distance between the wells takes no more than 1, calculated by the formula

of a dwelling house on a subsiding column of m, underlain at a depth of 22 m by dense sands of medium size.

Using a precast composite pile with a cross section of 0.35-0.35 m, 24 m long, with a grillage device in the form of a solid reinforced concrete slab in plan size of 1648 m, firstly the pit is dug under the building with broadening in each direction by 1 m, i.e. size in terms of 18-50m. Then proceed to the device of drainage wells, assigning their depth and level of backfill drainage material based on engineering and geological surveys. According to the latter, the subsiding stratum is composed mainly of sandy loam, with the relative subsidence of 2E 0.03 at a depth of 15 m and gross — 0.01 at a depth of 6 m. From this, the depth of the drainage wells h /

35

, 95dPd,

Pdcom pdw

(one)

PJ

com

de d - the diameter of the driving pile or

stuffed pile, - the minimum allowable value of the density of dry compacted soil, at which there is completely no drawdown from its own weight, usually taken in the upper part of the subsidence to a depth of 8-10 m equal to 1.5 tons / m, in the lower part, starting from a depth of 20 -25 m - 1.65 t / m, and in the middle part - by linear interpolation between these values;

the density of dry soil after compaction by pre-soaking, varying usually at a depth of 5-8 m from 1.45-1.5 t / m to 1.6 t / m per

depth of 20-25 m.

After placing the piles within the built-up area, based on the actual distance between them, using the formula (1), the achievable density values after the installation of the piles are determined (Figure 5).

Example. Carry out the method

„,

0

P

of a dwelling house on a subsiding column of m, underlain at a depth of 22 m by dense sands of medium size.

Using a precast composite pile with a cross section of 0.35-0.35 m, 24 m long, with a grillage device in the form of a solid reinforced concrete slab in plan size of 1648 m, firstly the pit is dug under the building with broadening in each direction by 1 m, i.e. size in terms of 18-50m. Then proceed to the device of drainage wells, assigning their depth and level of backfill drainage material based on engineering and geological surveys. According to the latter, the subsiding stratum is composed mainly of sandy loam, with the relative subsidence of 2E 0.03 at a depth of 15 m and gross — 0.01 at a depth of 6 m. From this, the depth of the drainage wells h /

five

they are equal to 15 m, and the depth from which the ground begins to sink because of its own weight, m. The density of dry soil in natural occurrence (graph 2) near the daytime height of PJ 1.4 t / m, at the lower boundary of the subsidence of 1.6 t / m, and at a depth of 10 m it decreases to 1.3 t / m, where the maximum relative subsidence of gg is 0.08 (figure 1). The maximum allowable density varies from 1.4 t / m near the surface to 1.6 t / m at a depth of 20 m.

Drainage wells with a depth of h of 15 m and a diameter of 40 cm are placed on a grid of 5–5 m. Based on these data, a value of 5 m is determined. The drilled wells, starting from a depth of (h –h) 2.5 m, are covered with coarse sand.

Soaking is done by pouring water into each well to the level of the top of the sand and keeping the water constant at that level. Since the subsidence of the soil is represented by sandy loams, they are soaked during the month. Alignment and reduction of soil moisture to 1,2Wp after stopping their soaking occurs within 5 days. Determination by the method of deep radioactive logging showed that the density is 0.01, by an amount where the soil in a dry state is the distance between wells, jb, its subsidence at a depth of 12 m increased to 1.45 t / m (Schedule 4).

After 2 m in depth, the maximum allowable distance between the edges is determined with the aim of additional consolidation of the subsidence soil, the minimum value of which is at a depth of 12 m according to the formula (1) 1.147 cm.

WITH

Based on this, the piles within the pile floor are slaughtered in a staggered order of 1.5 m.

angle of water spreading to the side of the well, and the piles are erected after the termination of the soil and its moisture content to a value not less than

20 1,2Wp, where WP is the soil moisture at the border of rolling, at the same time maximum spacings between them are prescribed with provision of additional soil compaction to a density in a dry state equal to 1.5-1.65 t / m.

2. Method POP.1, differing from that with the passage of the formula of the invention 1. Method of erecting the pile

On its contour in the soil they form a slit with a depth equal to 0.8 foundation on type II soils by pro-1.0 depth of the subsiding stratum of sediment, which includes a fragment of a cat- and fill it with low-filtration material, drilling, filling with rial.

their lower part is draining material, soaking the soil by supplying water to the wells and erecting a pile, which is characterized by the fact that

in order to reduce the labor intensity of the work and accelerate the construction of the foundation, the well is drilled to a depth starting from which the relative subsidence is the value

lower 0,015-0,03, the filling of wells with draining material is made to a level exceeding the level, and which relative subsidence

angle of water spreading to the side of the well, and the piles are erected after the termination of the soil and its moisture content to a value not less than

1.2Wp, where WP is the soil moisture at the border of rolling, at the same time the maximum spacing between them is prescribed to ensure the soil consolidation to the density in the dry state equal to 1.5-1.65 t / m.

2. Method POP.1, distinguishing US and with the fact that with a passage a cat. ..... h . .., f

V.; H jj} co ::: ;; V

I.Gorn

Thebes 1

id Compiled by V.Gonik

Tehred N.Glushchenko Proofreader M.Pojo

Order 1390/25 Circulation 607 Subscription of the USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Rauishka nab. d. 4/5

. Production and printing company, Uzhgorod, Projecto st., 4

Claims (2)

Claim 1. A method of erecting a pile foundation on type II soils by subsidence, including excavating a pit, drilling wells, backfilling the bottom with drainage material, soaking the soil by supplying water to the wells and erecting piles, characterized in that, 5, in order to reduce the complexity of the work and accelerate the construction of the foundation, the wells are drilled to a depth starting from which the relative subsidence is 10 less than 0.015-0.03, the wells are filled with drainage material to a level exceeding the level, and wherein the relative subsidence equal to 0.01, by the value h = ltgp, wherein 15 ί is the distance between the wells, · fi is the angle of water spreading to the sides of the well, and the piles are erected after the soil ceases and its moisture content decreases to a value not less than 20 1.2 Wp, where Wp is the soil moisture at the rolling border, while the maximum distances between piles, they are prescribed to ensure compaction of the soil to a density in the dry state equal to 1.5-1.65 t / m ^e . 2. The method according to claim 1, characterized in that when the pit is torn along its contour in the soil, a slot is formed with a depth equal to 0.830 1.0 of the depth of the subsidence thickness of the soil, and it is filled with low-filtering material. Tehred N. Glushchenko Corrector M. Pozho