Page 33 of 34
DESIGN RESISTANCE OF SOIL FOUNDATIONS
1. Calculated resistance of foundation soils R 0 given in table. 1-5, are intended for preliminary determination of the dimensions of foundations. Scope of values R 0 and R/ 0 for the final determination of the dimensions of the foundations is indicated in clause 2.42 for table. 4, in clause 8.4 for table. 5 and in paragraph 11.5 for table. 6.
2. For soils with intermediate values e And I L(Table 1-3), p d And S r(Table 4), S r(Table 5), as well as for foundations with intermediate values g(Table 6) values R 0 and R/ 0 are determined by interpolation.
3. Values R 0 (Table 1-5) refer to foundations with a width b 0 = 1 m and depth d 0 = 2 m.
When using values R 0 for the final assignment of foundation dimensions (clauses 2.42, 3.10 and 8.4) calculated resistance of the foundation soil R, kPa (kgf/cm2), determined by the formulas:
at d£ 2 m (200 cm)
R= R 0 x ( d+d 0)/2d 0 ; (1)
at d> 2 m (200 cm)
R= R 0 + k 2 g / II ( d-d 0), (2)
Where b And d- respectively the width and depth of the designed foundation, m (cm);
g / II - the calculated value of the specific gravity of the soil located above the base of the foundation, kN/m 3 (kgf/cm 3);
k 1 - coefficient accepted for foundations composed of coarse and sandy soils, except for silty sands, k 1 = 0.125, silty sands, sandy loams, loams and clays k 1 = 0,05;
k 2 - coefficient accepted for foundations composed of coarse and sandy soils, k 2 = 0.25, sandy loam and loam k 2 = 0.2 and clays k 2 = 0,15.
Note. For buildings with a basement width IN= 20 m and depth d b³ 2 m, the depth of external and internal foundations taken into account in the calculation is taken equal to: d = d 1 + 2 m [here d 1 - reduced depth of foundation, determined by formula (8) of these standards]. At IN> 20 m accepted d=d 1 .
Table 1
Calculated resistances R 0 coarse soils
| Coarse soils | Meaning R O, kPa (kgf/cm2) |
| Pebble (crushed stone) with filler: | |
| Sandy | |
| I L£0.5 | |
| 0,5 < I L£0.75 | |
| Gravel (wood) with filler: | |
| sandy | |
| silty-clayey with a fluidity index: | |
| I L£0.5 | |
| 0,5 < I L£0.75 |
table 2
Calculated resistances R 0 sandy soils
| Values R O, kPa (kgf/cm2), depending on the sand density |
||
| medium density |
||
| Medium size | ||
| Low moisture | ||
| wet and saturated with water | ||
| Dusty: | ||
| Low moisture | ||
| saturated with water | ||
Table 3
Calculated resistances R 0 silt-clay (non-subsidence) soils
| Silty-clayey | Coefficient Porosity e | Values R O, kPa (kgf/cm2), at soil fluidity index |
|
| Loams | |||
Table 4
Calculated resistances R 0 subsidence soils
| R O, kPa (kgf/cm2), soils |
||||
| Natural build with dry density p d, t/m 3 | compacted to dry density p d, t/m 3 |
|||
| 300 (3) | 350 (3,5) | |||
| Loams | 350 (3,5) | 400 (4) | ||
Note: The numerator shows values R O, relating to unsoaked subsidence soils with a degree of moisture S r£0.5; in the denominator - values R O related to the same soils with S r³ 0.8, as well as to soaked soils.
Table 5
Calculated resistances R 0 bulk soils
| R O, kPa (kgf/cm2) |
||||
| Characteristics | Large, medium-sized and fine sands, slags, etc. at humidity level S r | Silty sands, sandy loams, loams, clays, ash, etc. at humidity level S r |
||
| S r£0.5 | S r³ 0.8 | S r£0.5 | S r³ 0.8 |
|
| Embankments systematically constructed with compaction | ||||
| Dumps of soil and industrial waste: | ||||
| with seal | ||||
| without seal | ||||
| Landfills for soil and industrial waste: | ||||
| with seal | ||||
| without seal | ||||
Note: 1. Values R O in this table refer to bulk soils containing organic matter I om£0.1.
2. For unpacked dumps and landfills of soil and industrial waste, the values R O are accepted with a coefficient of 0.8.
Table 6
Calculated resistance of backfill soils R 0
for pull-out support foundations
overhead power lines
| Values, kPa (kgf/cm2) |
||||
| Relative depth of the foundation l = d/b | Silty-clayey soils with fluidity index I L£ 0.5 and backfill soil density, t/m 3 | Sands of medium coarseness and fine, low-moisture and wet sands with backfill soil density, t/m 3 |
||
Notes: 1. Values R O for clays and loams with a flow rate of 0.5 £ I L£0.75 and sandy loam at 0.5< I L£ 1.0 is accepted in the column “silt-clay soils” with the introduction of reduction factors of 0.85 and 0.7, respectively.
2. Values R O for silty sands are taken as for medium-sized and fine sands with a coefficient of 0.85.
| Content |
|---|
This is one of the most important parameters when building a foundation, as it allows you to determine the maximum possible values of the mass of the overlying structure that the underlying surface can support.
If the permissible values of the soil bearing capacity are exceeded, areas of limit equilibrium are formed under the base of the foundation. In other words, the soil located below cannot withstand the load and tends towards the direction of least resistance, that is, to the surface. The consequences are expressed in the form of mounds and shafts located near the boundaries of the foundation.
The most important danger in this case is the violation of the homogeneity of the underlying soil. The load from the structure begins to be distributed unevenly, the foundation loses its stability, deformation processes are activated and cracks soon begin to appear.
Calculation of soil bearing capacity
Determining the bearing capacity of the soil is a rather labor-intensive process that can be done using available means (manually/online) or using the services of geological and geodetic agencies!
We invite you to use our convenient online calculator for calculating the compressive/shear resistance of soil. At the end of the calculation, you will receive the value of the calculated resistance in four different units of measurement (kPa, kH/m 2, tf/m 2, kgf/cm 2). In order to get the calculation result, you need to fill in several fields:
- Calculation type. Based on laboratory tests or unknown soil characteristics.
- Soil characteristics. Type, porosity coefficient and fluidity index, as well as the average calculated value of the specific gravity of soils.
- Foundation parameters. Base width and depth.
The last two soil characteristics are determined only for clay soils.
Foundation soil resistance calculator
First, we need to select the calculation type. The first option implies that you will receive a soil sample and send it to a specialized laboratory for testing. This method takes a lot of time and money. Therefore, if you do not have a complex area and you are sure that you can do everything on your own, we suggest using the second option and performing the calculation based on tabular data.
Soil classification
The next stage of work is related to determining the type of soil. According to SNiP 11-15-74, all types of soils are divided into two main groups:
- rocky;
- non-rocky.
| The first are represented by rocks of metamorphic or granitic origin. They are found in mountainous areas and in places where the base of a tectonic platform reaches the surface (shields). In our country, this is the territory of Karelia and the Murmansk region. Mountain systems of the Urals, Caucasus, Altai, Kamchatka, plateaus of Siberia and the Far East. The resistance of rocky soils is so high that you may not need to make any preliminary calculations. |
| Non-rocky soils are found everywhere on the plains. They are divided into several types, and those in turn into factions:
|
How to determine the type of soil yourself?
There is a simple old-fashioned way to determine the type of soil that your parents and your parents’ parents used - it involves identifying the physical and mechanical properties of the rock.
To do this, it is necessary to take soil samples at the extreme points and in the middle of the site. Dig holes to the depth of the expected foundation level and take soil samples from each control point.
Prepare a work surface to conduct a science experiment.
- Wet the soil until it can be formed into a ball.
- Try to roll the ball into an oblong body (cord).
- If you were unable to do this, then in front of you sandy soil.
- If it sets a little, but still collapses - this is sandy loam.
- If the cord can be rolled into a ring, but breaks/cracks are observed - this is loam.
- If the ring is closed, but the body remains unharmed - this is clay.
For clarity, you can see the illustration below:
If you were unable to make anything from the soil sample, then the calculation of the bearing capacity of sandy soil is over for you. Select the appropriate item in the calculator and click " Calculate".
Soil bearing capacity - SNiP table
To determine the bearing capacity of clay soils, we need to obtain two more coefficients - soil fluidity index (I L) And porosity coefficient (e). The first indicator can be determined quite easily by eye; if the soil is frankly damp and viscous - choose I L = 1, if dry and rough - I L = 0. The second coefficient can only be obtained in tables from SNiP. Since all data is in the public domain, for your convenience we have copied tables of calculated soil resistance from SP 22.13330.2011.
Bearing capacity of clay soils
Clay soils | Porosity coefficient e | Values of R0, kPa, at soil fluidity index |
||
Sandy loam | ||||
Loams | ||||
Clays | ||||
Insert value porosity coefficient e into the calculator, enter the foundation parameters and complete the determination of the calculated soil resistance.
Bearing capacity of sandy soil
Sandy soils | R0 values, kPa, depending on the sand density |
||
dense | medium density |
||
Large | |||
Small | Low moisture | ||
Wet and saturated with water | |||
Dusty | Low moisture | ||
Saturated with water | |||
These table values of R 0 are valid for foundations with width b = 1 m and depth d = 2 m.
For other values of b and d, formulas must be used. At d<= 2 м используется первое выражение, при d >2 m - second.
Calculated soil resistance (formula) #1: R = R 0 × × (d + d 0) / 2d 0
Calculated soil resistance (formula) #2: R = R 0 × + k 2 × γ" II × (d - d 0)
In order to save you from complex cumbersome calculations, we have added a fourth item to our calculated soil resistance calculator, in which you can indicate the estimated dimensions of the foundation. Use our service and save your time!
The calculated electrical resistivity of the soil (Ohm*m) is a parameter that determines the level of “electrical conductivity” of the earth as a conductor, that is, how well the electric current from the ground electrode will flow in such an environment.
This is a measurable quantity that depends on the composition of the soil, size and density
the proximity of its particles to each other, humidity and temperature, the concentration of soluble chemicals in it (salts, acidic and alkaline residues).
Values of the calculated electrical resistivity of the soil (table)
| Priming | Resistivity, average value (Ohm*m) | ZZ-000-015, Ohm | Ground resistance for kit ZZ-000-030, Ohm | Ground resistance for kit ZZ-100-102, Ohm |
| Asphalt | 200 - 3 200 | 17 - 277 | 9,4 - 151 | 8,3 - 132 |
| Basalt | 2 000 | |||
| Bentonite (a type of clay) | 2 - 10 | 0,17 - 0,87 | 0,09 - 0,47 | 0,08 - 0,41 |
| Concrete | 40 - 1 000 | 3,5 - 87 | 2 - 47 | 1,5 - 41 |
| Water | ||||
| Sea water | 0,2 | 0 | 0 | 0 |
| Pond water | 40 | 3,5 | 2 | 1,7 |
| Lowland river water | 50 | 4 | 2,5 | 2 |
| Ground water | 20 - 60 | 1,7 - 5 | 1 - 3 | 1 - 2,5 |
| Permafrost soil (permafrost soil) | ||||
| Permafrost soil - thawed layer (near the surface in summer) | 500 - 1000 | - | - | 20 - 41 |
| Permafrost soil (loam) | 20 000 | Special measures are required (soil replacement) | ||
| Permafrost soil (sand) | 50 000 | Special measures are required (soil replacement) | ||
| Clay | ||||
| Clay wet | 20 | 1,7 | 1 | 0,8 |
| Semi-solid clay | 60 | 5 | 3 | 2,5 |
| Gneiss decomposed | 275 | 24 | 12 | 11,5 |
| Gravel | ||||
| Clay gravel, heterogeneous | 300 | 26 | 14 | 12,5 |
| Homogeneous gravel | 800 | 69 | 38 | 33 |
| Granite | 1 100 - 22 000 | Special measures are required (soil replacement) | ||
| Granite gravel | 14 500 | Special measures are required (soil replacement) | ||
| Gra f vitreous chips | 0,1 - 2 | 0 | 0 | 0 |
| Grass (fine crushed stone/coarse sand) | 5 500 | 477 | 260 | 228 |
| Ash, ashes | 40 | 3,5 | 2 | 1,7 |
| Limestone (surface) | 100 - 10 000 | 8,7 - 868 | 4,7 - 472 | 4,1 - 414 |
| Limestone (inside) | 5 - 4 000 | 0,43 - 347 | 0,24 - 189 | 0,21 - 166 |
| IL | 30 | 2,6 | 1,5 | 1 |
| Coal | 150 | 13 | 7 | 6 |
| Quartz | 15 000 | Special measures are required (soil replacement) | ||
| Coke | 2,5 | 0,2 | 0,1 | 0,1 |
| Loess (yellow soil) | 250 | 22 | 12 | 10 |
| Chalk | 60 | 5 | 3 | 2,5 |
| Marl | ||||
| Common marl | 150 | 14 | 7 | 6 |
| Clay marl (50 - 75% clay particles) | 50 | 4 | 2 | 2 |
| Sand | ||||
| Sand heavily moistened by groundwater | 10 - 60 | 0,9 - 5 | 0,5 - 3 | 0,4 - 2,5 |
| Sand, moderately moistened | 60 - 130 | 5 - 11 | 3 - 6 | 2,5 - 5,5 |
| Wet sand | 130 - 400 | 10 - 35 | 6 - 19 | 5 - 17 |
| The sand is slightly damp | 400 - 1 500 | 35 - 130 | 19 - 71 | 17 - 62 |
| Sand dry | 1 500 - 4 200 | 130 - 364 | 71 - 198 | 62 - 174 |
| Sandy loam (sandy loam) | 150 | 13 | 7 | 6 |
| Sandstone | 1 000 | 87 | 47 | 41 |
| garden soil | 40 | 3,5 | 2 | 1,7 |
| Saline | 20 | 1,7 | 1 | 0,8 |
| Loam | ||||
| Loam, highly moistened by groundwater | 10 - 60 | 0,9 - 5 | 0,5 - 3 | 0,4 - 2,5 |
| Semi-solid loam, forest-like | 100 | 9 | 5 | 4 |
| Loam at a temperature of minus 5 C° | 150 | - | - | 6 |
| Sandy loam (sandy loam) | 150 | 13 | 7 | 6 |
| Slate | 10 - 100 | |||
| Slate gras f ite | 55 | 5 | 2,5 | 2,3 |
| Sandy loam (sandy loam) | 150 | 13 | 7 | 6 |
| Peat | ||||
| Peat at a temperature of 10° | 25 | 2 | 1 | 1 |
| Peat at 0 C° | 50 | 4 | 2,5 | 2 |
| Chernozem | 60 | 5 | 3 | 2,5 |
| Crushed stone | ||||
| Wet crushed stone | 3 000 | 260 | 142 | 124 |
| Dry crushed stone | 5 000 | 434 | 236 | 207 |
Ground resistance for sets ZZ-000-015 and ZZ-000-030, indicated in the table can be used
with different grounding configurations - both point and multi-electrode.
Together with a table of approximate values for the calculated soil resistivity, we offer you
use a geographic map of previously installed grounding electrodes based on ready-made ZANDZ grounding kits
with the results of grounding resistance measurements.
Soil types in the Republic of Kazakhstan
and their electrical resistivities (map)
|
|
The design resistance of a foundation made of non-rocky soils to axial compression is determined by the formula
Where 
- conditional soil resistance, kPa;
,
- coefficients accepted according to Table 11;
- width (smaller side or diameter) of the foundation base, m;
- foundation depth, m;
- calculated value of the specific gravity of the soil averaged over layers,
located above the base of the foundation, calculated without taking into account
suspended action of water;
allowed to accept 
=19.62 kN/m3.
When determining the design resistance, the foundation depth should be taken for intermediate bridge supports - from the soil surface at the support at the cutting level within the foundation contour, and in river beds - from the bottom of the watercourse at the support after lowering its level to the depth of the general and half the local erosion of the soil during estimated expense. Design resistances calculated using formula (24) for clays and loams in the foundations of bridges located within permanent watercourses should be increased by an amount equal to 14.7 
, kPa, 
- water depth from the lowest low-water level to the bottom of the watercourse
Values of conditional soil resistances 
are determined according to SNiP 2.05.03-84 (Tables 9, 10) depending on the type, type and variety for sandy soils and the type, value of the porosity coefficient e and turnover rate
for silty-clayey soils. For intermediate values e And
quantities 
determined by interpolation. At plasticity number values
within 5-10 and 15-20 average values should be taken 
, given respectively for sandy loam, loam and clay. For dense sands 
should be increased by 60% if their density is determined based on the results of laboratory soil tests. For loose sandy soils and silty clay soils in a fluid state ( 
> 1) or with porosity coefficient e
> e max (where e max – maximum tabulated value of the porosity coefficient for a given soil type) conditional resistance 
not standardized. These soils are considered weak soils, which cannot be used as a natural foundation without special measures.
Table 1.3.1. – Extract from table 1 appendix 24 SNiP 2.05.03-84
|
Coefficient porosity e |
Conditional resistance
R 0, silt-clay (non-subsidence) foundation soils, kPa depending on the fluidity index |
|||||||
|
Arrogance at
| ||||||||
|
Loams at 10 ≤
| ||||||||
|
Clays at
| ||||||||
≤5
≤
15
≥20Table 1.3.2. – Extract from table 2 appendix 24 SNiP 2.05.03-84
|
Sandy soils and their moisture content |
Conditional resistance R 0 sandy soils of medium density at the base, kPa |
|
Gravelly and large regardless of their moisture content | |
|
Medium size: low moisture wet and saturated with water | |
|
Small: low moisture wet and saturated with water | |
|
Dusty: low-moisture saturated with water | |
Table 1.3.3. – Extract from table 4 appendix 24 SNiP 2.05.03-84
|
Odds |
||
|
|
|
|
|
1. Gravel, pebbles, gravelly sand, coarse and medium-sized | ||
|
2. Fine sand | ||
|
3. Silty sand, sandy loam | ||
|
4. Loam and clay: hard and semi-hard | ||
|
5. Loam and clay: hard-plastic and soft-plastic | ||
, m -1
, m -1Example 1.3.1. Determine the design resistance to axial compression of a foundation made of low-moisture sand of medium coarseness under the base of a shallow foundation for an intermediate support of a road bridge, if given: foundation width 
its depth 
the calculated value of the specific gravity of the soil located above the base of the foundation, averaged over layers, 
=19.6 kN/m3.
Solution. For low-moisture sand of medium size according to table. 1.3.2 we find R 0 =294 kPa, and according to Table 1.3.3 - coefficient values 
=0.10 m -1 and 
=3.0 m -1 .
The calculated resistance of the soil foundation is determined by the formula
Example 1.3.2. Determine the design resistance to axial compression of a base made of refractory loam under the base of the foundation from the sinkhole of the intermediate support of a road bridge located in a permanent watercourse, if given: width of the foundation 
its depth 
loam fluidity index 
plasticity number 
=0.12, porosity coefficient 
=0.55, calculated value of the specific gravity of the soil located above the base of the foundation, averaged over layers, 
= 19.6 kN/m 3, water depth from the lowest low-water level 
=5 m.
Solution. From the table 1.3.2 by interpolation we find the conditional resistance 
refractory loam with 
And 
=0,55.
From Table 1.3.3 – coefficient values 
=0.02 m -1 and 
=1.5 m -1.
Taking into account the loading of the loam layer with water, the calculated resistance of the soil foundation will be determined by the formula
11. Medium (within the compressible thickness N s or layer thickness N) the values of the deformation modulus and Poisson's ratio of foundation soils ( and ) are determined by the formulas:
; (11)
Where Ai- area of the diagram of vertical stresses from a unit pressure under the base of the foundation within i th layer of soil; for a half-space diagram it is allowed to take Ai = s zp,ih i(see point 1), for the layer diagram – Ai= k i- k i- 1 (see clause 7);
E i,v i,h i, - deformation modulus, Poisson's ratio and thickness, respectively i th layer of soil;
N - calculated layer thickness, determined according to clause 8;
n- number of layers with different values E And v within the compressible thickness H with or layer thickness H.
DETERMINATION OF subsidence of foundation soils
12. Soil subsidence s sl bases with an increase in their humidity due to soaking large areas from above (see paragraphs 3.2 and 3.5), as well as soaking from below when the groundwater level rises, is determined by the formula
(13)
Where e sl,i– relative subsidence i th layer of soil, determined in accordance with the instructions in paragraph 13;
h i– thickness i th layer;
k sl,i– coefficient determined in accordance with the instructions in clause 14;
n– number of layers into which the subsidence zone is divided h sl, accepted in accordance with the instructions of clause 16.
13. Relative soil subsidence e sl determined based on tests of soil samples for compression without the possibility of lateral expansion according to the formula
, (14)
Where h n,p And h sat,p-- height of the sample according to natural humidity and after its complete saturation with water ( w=w sat) at pressure p, equal to the vertical stress at the considered depth from the external load and the soil’s own weight p = s zp + s zg– when determining soil subsidence in the upper subsidence zone; when determining soil subsidence in the lower subsidence zone, the additional load from negative friction forces is also taken into account (see paragraphs 3.4 and 3.8);
h n,g- height of the same sample of natural humidity at p = s zg.
Relative subsidence of soil when it is incompletely saturated with water ( w sl=w<w sat) - e / sl determined by the formula
, (15)
Where w– soil moisture;
w sat– humidity corresponding to complete water saturation of the soil;
w sl– initial subsidence moisture (clause 3.3);
e sl– relative subsidence of the soil when it is completely water-saturated, determined by formula (14).
14*. Coefficient k sl,i, included in formula (13):
at b= 12 m – taken equal to 1 for all soil layers within the subsidence zone;
at b= 3 m – calculated by the formula
Where R – average pressure under the base of the foundation, kPa (kgf/cm2);
p sl,i– initial subsidence soil pressure i th layer, kPa (kgf/cm2), determined in accordance with the instructions in paragraph 15;
R 0 – pressure equal to 100 kPa (1 kgf/cm2);
at 3 m< b < 12 м – определяется по интерполяции между значениями k sl,i, obtained with b= 3 m and b= 12 m.
When determining soil subsidence due to its own weight, one should take k sl= 1 at H sl£15m and k sl= 1.25 at H sl³ 20 m, with intermediate values Nsl coefficient k sl determined by interpolation.
15. For the initial subsidence pressure p sl the pressure corresponding to:
during laboratory tests of soils in compression devices - the pressure at which the relative subsidence e sl equal to 0.01;
during field testing with stamps of pre-soaked soils - a pressure equal to the limit of proportionality on the load-settlement graph;
when soaking soils in experimental pits - vertical stress from the soil’s own weight at the depth from which subsidence of the soil from its own weight occurs.
Rice. 4. Schemes for calculating foundation subsidence
A a– there is no subsidence from its own weight (does not exceed 5 cm), only subsidence from external load is possible s sl,р in the upper drawdown zone h sl,p(I type of soil conditions); b,V, G, - possible subsidence due to its own weight s sl,g in the lower drawdown zone h sl,g, starting from depth z g(II type of soil conditions); b– the upper and lower drawdown zones do not merge, there is a neutral zone h n; V– the upper and lower subsidence zones merge; G– there is no subsidence from external load; 1 - vertical stresses from the soil’s own weight s zg ; 2 – total vertical stresses from external load and soil’s own weight s z = s zp+ s zg; 3 – change with depth of initial subsidence pressure p sl; Nsl d – foundation depth.
16. Thickness of the subsidence zone h sl is assumed to be equal (Fig. 4)
h sl = h sl,R– thickness of the upper subsidence zone when determining soil subsidence from external load s sl,p(clause 3.4), while the lower boundary of the specified zone corresponds to the depth where s z = s zp+ s zg= p sl(Fig. 4 A,b) or depth, where the value atz minimal if s z,min> p sl(Fig. 4, V);
h sl = h sl,g – thickness of the lower subsidence zone when determining soil subsidence from its own weight s sl ,g(clauses 3.4, 3.5), i.e. starting from depth z g, Where s z = p sl or meaning s z minimal if s z,min> p sl, and to the lower boundary of the subsidence strata.
17. Possible subsidence of soil from its own weight s/st,g when soaking small areas from above (width of the soaked area B w less than the size of the subsidence thickness N sl) is determined by the formula
Where s sl,g- the maximum value of soil subsidence due to its own weight, determined in accordance with clause 12.
DETERMINATION OF DEFORMATIONS OF FOUNDATIONS,
COMPLETED BY SWIMMING SOILS
18. Raising the base when the soil swells h sw determined by the formula
, (18)
Where e sw,i- relative soil swelling i th layer, determined in accordance with the instructions in paragraph 19;
h i- thickness i- th layer of soil;
k sw,i- coefficient determined in accordance with the instructions in clause 20;
n- the number of layers into which the soil swelling zone is divided.
19. Relative soil swelling e sw determined by the formulas:
with moisture infiltration
, (19)
Where h n– height of a sample of natural humidity and density, compressed without the possibility of lateral expansion by pressure R, equal to the total vertical stress atz,tot at the considered depth (value atz,tot determined in accordance with the instructions in paragraph 21);
hsat– the height of the same sample after soaking until complete water saturation, compressed under the same conditions;
when shielding the surface and changing the water-thermal regime
, (20)
Where k- coefficient determined experimentally (in the absence of experimental data, it is accepted k = 2);
w eq- final (steady) soil moisture;
w 0 and e 0 - respectively, the initial values of soil moisture and porosity coefficient.
20. Coefficient k sw, included in formula (18), depending on the total vertical stress s z,tot at the depth under consideration, is taken equal to 0.8 at s z,tot= 50 kPa (0.5 kgf/cm 2) and 0.6 at s z,tot= 300 kPa (3 kgf/cm 2), and at intermediate values s z,tot- by interpolation.
21. Total vertical stress s z,tot at a depth z from the base of the foundation (Fig. 5) is determined by the formula
, (21)
Where s zр,s zg - vertical stresses, respectively, from the load of the foundation and from the own weight of the soil;
atz,ad- additional vertical pressure caused by the influence of the weight of the unwetted part of the soil mass outside the soaking area, determined by the formula
, (22)
Where k g- coefficient accepted according to the table. 6.
Table 6
Coefficient k g
|
(d+ z) / Bw |
Coefficient k g for the ratio of length to width of the soaked area L w / B w, equal |
|||||
22. Lower boundary of the swelling zone H sw(Fig. 5):
a) during moisture infiltration is taken at a depth where the total vertical stress s z,tot(item 21) is equal to the swelling pressure p sw;
b) when shielding the surface and changing the water-thermal regime - determined experimentally (in the absence of experimental data, it is accepted H sw= 5 m).
Rice. 5. Scheme for calculating the rise of the base during soil swelling
23.Settlement of the base as a result of drying of the swollen soil s sh determined by the formula
, (23)
Where e sh,i– relative linear shrinkage of soil i th layer, determined in accordance with the instructions in paragraph 24;
h i– thickness i th layer of soil;
ksh– coefficient taken equal to 1.3;
n– the number of layers into which the soil shrinkage zone is divided, taken in accordance with the instructions in clause 25.
24. The relative linear shrinkage of soil when it dries is determined by the formula
, (24)
Where h n- the height of the soil sample with the highest possible moisture content when compressed by the total vertical stress without the possibility of lateral expansion;
h d- height of the sample under the same conditions after decreasing humidity as a result of drying.
25. Lower limit of the shrinkage zone Hsh is determined experimentally, and in the absence of experimental data is taken equal to 5 m.
When the soil dries out as a result of the thermal effect of technological installations, the lower boundary of the shrinkage zone Hsh determined empirically or by appropriate calculation.
DETERMINATION OF SUFFOSION SEDIMENT
26. Suffusion sediment s sf foundation composed of saline soils is determined by the formula
Where e sf,i- relative suffusion compression of soil i th layer at pressure R, equal to the total vertical stress at the considered depth from the external load s zp and the soil's own weight s zg, determined according to the instructions of clause 27;
h i- thickness i- th layer of saline soil;
n- the number of layers into which the zone of suffusion sedimentation of saline soils is divided.
27. Relative suffosion compression e sf defined:
a) during field tests with a static load with long-term soaking according to the formula
Where s sf,p– suffusion stamp settling under pressure;
p= s zp + s zg;
d p– zone of suffusion sedimentation of the base under the stamp;
b) during compression and filtration tests according to the formula
, (27)
Where h sat,p- height of the sample after soaking (full water saturation) at pressure p= s zp + s zg;
h sf,p- height of the same soil sample after long-term filtration of water and leaching of salts under pressure p.
h ng- height of the same sample of natural humidity at pressure p i=y zg.
DESIGN RESISTANCE OF SOIL FOUNDATIONS
1. Calculated resistance of foundation soils R 0 given in table. 1-5, are intended for preliminary determination of the dimensions of foundations. Scope of values R 0 and R/ 0 for the final determination of the dimensions of the foundations is indicated in clause 2.42 for table. 4, in clause 8.4 for table. 5 and in paragraph 11.5 for table. 6.
2. For soils with intermediate values e And I L(Table 1-3), p d And S r(Table 4), S r(Table 5), as well as for foundations with intermediate values g (Table 6) values R 0 and R/ 0 are determined by interpolation.
3. Values R 0 (Table 1-5) refer to foundations with a width b 0 = 1 m and depth d 0 = 2 m.
When using values R 0 for the final assignment of foundation dimensions (clauses 2.42, 3.10 and 8.4) calculated resistance of the foundation soil R, kPa (kgf/cm2), determined by the formulas:
at d £ 2 m (200 cm)
R= R 0 x ( d+d 0)/2d 0 ; (1)
at d> 2 m (200 cm)
R= R 0 + k 2 g / II ( d-d 0), (2)
Where b And d– respectively the width and depth of the designed foundation, m (cm);
g / II – calculated value of the specific gravity of the soil located above the base of the foundation, kN/m 3 (kgf/cm 3);
k 1 – coefficient accepted for foundations composed of coarse and sandy soils, except for silty sands, k 1 = 0.125, silty sands, sandy loams, loams and clays k 1 = 0,05;
k 2 – coefficient accepted for foundations composed of coarse and sandy soils, k 2 = 0.25, sandy loam and loam k 2 = 0.2 and clays k 2 = 0,15.
Note. For buildings with a basement width IN= 20 m and depth d b ³ 2 m, the depth of external and internal foundations taken into account in the calculation is taken equal to: d = d 1 + 2 m [here d 1 – reduced depth of foundation, determined by formula (8) of these standards]. At IN> 20 m accepted d=d 1 .
Table 1
Calculated resistances R 0 coarse soils
|
Coarse soils |
R O value, kPa (kgf/cm2) |
|
Pebble (crushed stone) with filler: |
|
|
Sandy |
|
|
I L £0.5 |
|
|
0,5 < I L£0.75 |
|
|
Gravel (wood) with filler: |
|
|
sandy |
|
|
silty-clayey with a fluidity index: |
|
|
I L £0.5 |
|
|
0,5 < I L£0.75 |
table 2
Calculated resistances R 0 sandy soils
|
R O values, kPa (kgf/cm2), depending on the sand density |
||
|
medium density |
||
|
Medium size |
||
|
Low moisture |
||
|
wet and saturated with water |
||
|
Dusty: |
||
|
Low moisture |
||
|
saturated with water |
||
Table 3
Calculated resistances R 0 silt-clay (non-subsidence) soils
|
Silty-clayey |
Coefficient Porosity e |
Values of R O, kPa (kgf/cm2), at soil fluidity index |
|
|
Loams |
|||
Table 4
Calculated resistances R 0 subsidence soils
|
R O, kPa (kgf/cm 2), soils |
||||
|
Natural build with dry density p d, t/m 3 |
compacted to dry density p d, t/m 3 |
|||
|
Loams |
||||
Note: The numerator shows values R O, relating to unsoaked subsidence soils with a degree of moisture S r£0.5; in the denominator - values R O related to the same soils with S r ³ 0.8, as well as to soaked soils.
Table 5
Calculated resistances R 0 bulk soils
|
R O, kPa (kgf/cm2) |
||||
|
Characteristics |
Large, medium-sized and fine sands, slags, etc. at humidity level S r |
Silty sands, sandy loams, loams, clays, ash, etc. at humidity degree S r |
||
|
S r £0.5 |
S r ³ 0.8 |
S r £0.5 |
S r ³ 0.8 |
|
|
Embankments systematically constructed with compaction |
||||
|
Dumps of soil and industrial waste: |
||||
|
with seal |
||||
|
without seal |
||||
|
Landfills for soil and industrial waste: |
||||
|
with seal |
||||
|
without seal |
||||
Note: 1. Values R O in this table refer to bulk soils containing organic matter I om £0.1.
2. For unpacked dumps and landfills of soil and industrial waste, the values R O are accepted with a coefficient of 0.8.
Table 6
Calculated resistance of backfill soils R 0
for pull-out support foundations
overhead power lines
|
Values, kPa (kgf/cm2) |
||||
|
Relative depth of foundation l = d/b |
Silty-clayey soils with fluidity index I L £ 0.5 and backfill soil density, t/m 3 |
Sands of medium coarseness and fine, low-moisture and wet sands with backfill soil density, t/m 3 |
||
Notes: 1. Values R O for clays and loams with a flow index of 0.5 £ I L£0.75 and sandy loam at 0.5 < I L£ 1.0 is accepted in the column “silt-clay soils” with the introduction of reduction factors of 0.85 and 0.7, respectively.
2. Values R O for silty sands are taken as for medium-sized and fine sands with a coefficient of 0.85.
MAXIMUM BASE DEFORMATIONS
|
Limit deformations of the base |
|||
|
Facilities |
relative difference in precipitation (D s/L)u |
Bank i u |
(maximum s max,u in parentheses) draft, cm |
|
1. Industrial and civil single-story and multi-story buildings with a full frame: reinforced concrete steel |
|||
|
2. Buildings and structures in the structures of which forces do not arise from uneven settlements |
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|
3. Multi-storey frameless buildings with load-bearing walls made of: large panels large blocks or brickwork without reinforcement the same, with reinforcement, including the installation of reinforced concrete belts |
|||
|
4. Construction of elevators with reinforced concrete structures: work building and silo building of monolithic structure on one foundation slab the same, prefabricated structure free-standing silo housing of monolithic design the same, prefabricated structure detached work building |
|||
|
5. Chimney height N, m: N £100 100 < N £200 200 < N £300 N > 300 |
|||
|
6. Rigid structures up to 100 m high, except those indicated in pos. 4 and 5 |
|||
|
7. Antenna communication structures: grounded mast trunks the same, electrically insulated radio towers shortwave radio towers towers (separate blocks) |
|||
|
8. Supports of overhead power lines: intermediate straight lines anchor and anchor-corner, intermediate corner, end, portals of open distribution devices special transitional |
|||
Notes: 1. Limit values of the relative deflection (camber) of buildings specified in pos. 3 of this appendix are taken equal to 0.5 ( D s/L)u .
2. When determining the relative difference in sediment ( D s/L) in pos. 8 of this application for L the distance between the axes of the foundation blocks in the direction of horizontal loads is taken, and in supports with guy wires - the distance between the axes of the compressed foundation and the anchor.
3. If the base is composed of horizontal (with a slope of no more than 0.1) soil layers maintained in thickness, the maximum and average settlement limits may be increased by 20%.
4. Limit values for the rise of a foundation composed of swelling soils are allowed to be accepted: maximum and average rise of 25% and relative uneven settlement (relative deflection) of the building in the amount of 50% of the corresponding limit values of deformations given in this annex.
5. For structures listed in pos. 1-3 of this appendix, with foundations in the form of solid slabs, the maximum values of average settlement can be increased by 1.5 times.
6. Based on generalization of experience in the design, construction and operation of certain types of structures, it is allowed to accept limit values for foundation deformations that differ from those specified in this annex.
BASIC LETTER DESIGNATIONS
RELIABILITY RATIO
g f– by load;
g m– according to the material;
g g– on the ground;
g n– according to the purpose of the structure;
g With– coefficient of working conditions.
SOIL CHARACTERISTICS
– average value of the characteristic;
X n– normative value;
X– calculated value;
a – confidence probability (security) of calculated values;
R– density;
p d– dry density;
p bf– backfill density;
e– density coefficient;
w– natural humidity;
w p– humidity at the boundary of plasticity (rolling);
w L– humidity at the yield boundary;
w eq– final (steady) humidity;
w sat– humidity corresponding to complete water saturation;
w sl– initial subsidence moisture content;
w sw– swelling moisture;
w sh– humidity at the shrinkage limit;
S r– degree of humidity;
I L– turnover rate;
g – specific gravity;
g sb– specific gravity taking into account the weighing effect of water;
p sl– initial subsidence pressure;
p sw – swelling pressure;
e sl– relative subsidence;
e sw– relative swelling;
e sh– relative linear shrinkage;
e sf– relative suffusion compression;
I from– relative content of organic matter;
Dpd– degree of decomposition of organic matter;
With– specific adhesion;
j – angle of internal friction;
E– deformation modulus;
v- Poisson's ratio;
Rc– ultimate uniaxial compressive strength of rocky soils;
with v– consolidation coefficient.
LOADS, VOLTAGES, RESISTANCE
F– force, calculated value of force;
f– force per unit length;
F v , F h– vertical and horizontal components of force;
F s,a ,F s,r– forces acting along the sliding plane, respectively shearing and holding (active and reactive);
N– force normal to the base of the foundation;
n– the same, per unit length;
G– own weight of the foundation;
q– evenly distributed vertical load;
R– average pressure under the base of the foundation;
s – normal voltage;
t – shear stress;
And– excess pressure in pore water;
s z– vertical normal stress is complete;
s zg
s zp– the same, additional from external load (foundation pressure);
R– design resistance of the foundation soil (limit of the linear “load-settlement” relationship);
R 0 – calculated soil resistance (for preliminary determination of the dimensions of foundations), taken in accordance with the recommended Appendix 3;
F and– the force of ultimate resistance of the foundation, corresponding to the exhaustion of its bearing capacity.
DEFORMATION OF FOUNDATIONS AND STRUCTURES
s– foundation settlement;
– average foundation settlement;
s sl– drawdown;
h sw– rise of the base when the soil swells;
s sh– settlement of the base as a result of drying out of the swollen soil;
s sf– suffusion sediment;
D s– difference in settlement (subsidence);
i– tilt of the foundation (structure);
J – relative twist angle;
And– horizontal movement;
s and– limiting value of base deformation;
s and,s– the same, according to technological requirements;
s and,f– the same, according to the conditions of strength, stability and crack resistance of structures.
GEOMETRICAL CHARACTERISTICS
b– width of the foundation base;
IN– width of the basement;
B w– width of the soaking source (soaked area);
l– length of the base of the foundation;
h = l/b– aspect ratio of the base of the foundation;
A– area of the foundation base;
L– length of the building;
d,d n,d 1 – the depth of the foundation, respectively, from the planning level, from the surface of the natural relief and given from the basement floor;
d b– depth of the basement from the planning level;
d f, dfn– depth of seasonal soil freezing, calculated and standard, respectively;
d w– depth of groundwater level;
l = d/b– relative depth of the foundation;
h– thickness of the soil layer;
N s– depth of compressible thickness;
N– thickness of the linearly deformable layer;
H sl– thickness of the subsidence soil layer (subsidence thickness);
h sl– thickness of the subsidence zone;
h sl,p– the same, from external load;
h sl,g– the same, from the soil’s own weight;
H sw– thickness of the swelling zone;
Hsh– the same, shrinkage;
z– depth (distance) from the base of the foundation;
z = 2z/b– relative depth;
D.L.– planning mark;
NL– marking the surface of the natural relief;
FL– mark of the base of the foundation;
B, C – lower boundary of the compressible thickness;
B,SL– the same, subsidence strata;
B, S.W.– lower boundary of the swelling zone;
B, SH– the same, shrinkage zones;
W.L.– groundwater level.
1. General Provisions
2. Design of foundations
General instructions
Loads and impacts taken into account in foundation calculations
Standard and calculated values of soil characteristics
The groundwater
Foundation depth
Calculation of foundations based on deformations
Calculation of foundations based on bearing capacity
Measures to reduce foundation deformations and their impact on structures
3. Features of designing the foundations of structures erected on subsidence soils
4. Features of designing the foundations of structures erected on swelling soils
5. Features of designing the foundations of structures erected on water-saturated biogenic soils and silts
6. Features of designing the foundations of structures erected on eluvial soils
7. Features of designing the foundations of structures erected on saline soils
8. Features of designing the foundations of structures erected on bulk soils
9. Features of designing the foundations of structures erected in mined areas
10. Features of designing the foundations of structures erected in seismic areas
11. Features of designing the foundations of overhead power transmission line supports
12. Features of designing foundations for bridge supports and pipes under embankments
13*. Features of designing the foundations of structures erected in karst areas
14*. Features of designing the foundations of structures erected on heaving soils
15*. Features of designing the foundations of structures erected on alluvial soils
16*. Design of soil stabilization
17*. Design of artificial soil freezing
18*. Dewatering design
Appendix 1. Standard values of strength and deformation characteristics of soils
Appendix 2. Calculation of foundation deformations
Appendix 3. Calculated resistance of foundation soils
Appendix 4. Limit deformations of the base
Appendix 5. Basic letter designations