Build Daily


August 12, 2017 18:06

The coefficient of loosening the soil : an example calculation for construction

Construction work begins with the markup site and excavation for the foundation.Excavations also occupied first place in the construction cost estimates, and a considerable amount of money is necessary to pay for technology that produces the recess and removal of soil from the site.For budgeting and evaluation of the cost of work not enough to know the dimensions of the pit, you must also take into account the peculiarities of the soil.One such characteristic is the rate of soil loosening, allowing to determine the increase in volume during the recess him out of the pit

The coefficient of soil loosening

factor loosening soil

all soils from the point of view of the construction can be divided into two groups:

  • cemented, or rock -stone rocks, the development of which is possible only with the explosion of technology or crushing;
  • unconsolidated, which is carried out sample by hand or with the help of excavators, bulldozers and other heavy machinery.These include sand, clay, mixed types of soils.

on design complexity and cost o

f digging the soil affect the following properties:

  • humidity - the ratio of the mass of water contained in the soil, to the mass of particulate matter;
  • Clutch - shear resistance;
  • density, ie, the mass of one cubic meter of soil in its natural state;
  • Razryhlyaemost - the ability to expand and develop during recess.

soil moisture - it is a measure of water saturation, expressed as a percentage.Normal humidity is in the range of 5-25%, and the primers having humidity greater than 30% are considered as wet.When humidity up to 5% soils are called dry.

wet soil sample

Sample wet soil

Strength affects the soil shear strength, at the sand and sandy loam, the figure is in the range of 3-50 kPa, in clay and loam - in the range 5-200 kPa.

density depends on the qualitative and quantitative composition of the soil, as well as its moisture.The most dense, and therefore heavy soils are rocky, the lightest category of soil - sands and sandy loams.Characteristics of soil are given in the table:

Table - different soil categories

Table - the different categories of soil

As the table shows, the ratio of the initial loosening of the soil is directly proportional to density of the soil, in other words, the denser and heavier the soil under natural conditions, the more volume it takes inselected state.This setting affects the volume of soil removal after development.

There is also an indicator such as residual soil loosening, it shows how susceptible the soil sediment in the process of caking, in contact with water, compaction machinery.For residential buildings, the figure is set at a gravel order to perform a pillow under the foundation and other work related to the calculation of imported soil.Also, it is important for the storage and disposal of soils.

Table - name of the soil and its residual loosening %

Table - soil name and its residual loosening%

Example of calculating the coefficient of loosening soil

Application factors of initial and residual soil loosening in practice can be considered an example of calculation.Suppose that there is a need to fulfill the development of the soil under recessed pit strip foundation with subsequent dumping gravel cushion.The soil in the area - the wet sand.The width of the pit - 1 meter, the total length of 40 meters of the foundation tape, excavation depth - 1.5 meters, the thickness of the gravel cushion tamped - 0.3 meters.

  • find the volume of excavation and therefore the ground in its natural state:
VR = 1 · 40 · 1.5 = 60 m3.
  • Applying the ratio of the initial loosening of the soil is determined by its volume after development:
V1 = kp · VR = 1.2 × 60 = 72 m3;

where kp = 1,2 - coefficient of the initial loosening of soil wet sand, adopted by the average value (Table 1).

Consequently, the export volume of the soil will be 72m3.

  • find the final volume of the gravel cushion after tamping:
vn = 1 · 40 · 0.3 = 12 m3.
  • Reading of the table 2 and the maximum value of the initial residual loosening factor for gravel and pebble soil and express them as fractions.

initial loosening factor kp = 20% or 1.2;residual loosening factor kor = 8% or 1.08.

  • calculate the amount of gravel to carry gravel cushion a final volume of 12 m3.
V2 = Vp · kp / kor · 1.2 = 12 / 1.08 = 13.33 m3.

Therefore, the amount required to be dumping gravel 13,3m3.

Of course, this calculation is very rough, but it will give you an idea of ​​what the coefficient of soil loosening, and what it is used.In the design of a cottage or an apartment house used a more complex method, but for preliminary calculation of materials and labor for the construction of a garage or a country house, you can use it.