Is the consolidation coefficient of soil;

K is the permeability coefficient;

γw is the gravity of water, and the general approximate value is equal to10.0kn/m3;

E is the natural porosity ratio;

A is the compression coefficient;

Under the action of external load, the soil is compacted and deformed due to the decrease of void ratio, and the strength is improved. For saturated soil, deformation will only occur after pore water is squeezed out. At the beginning, all the stresses in the soil are borne by the pore water.

With the extrusion of pore water, pore water pressure is gradually transformed into effective stress on soil skeleton. It is called soil consolidation theory to study the mutual growth and decline of these two stresses and the process of soil deformation reaching the final value.

In one-dimensional consolidation theory (see soil consolidation theory for details), pore water mainly flows in the vertical direction. K Karl Terzaghi (translated by Taishaki) established the one-dimensional consolidation differential equation of pore water pressure U, depth Z and time T according to the condition that the flow change of differential unit in saturated soil is equal to the change rate of void ratio.

formula

Is the coefficient of consolidation.

; K is the vertical permeability coefficient; E is porosity; A is the compression coefficient;

Is the bulk density of water. Among them, the dissipation rate u of pore water pressure is related to the permeability coefficient k of soil and the compressive modulus of soil.

=( 1+e)/a is proportional. With the gradual consolidation of clay layer, K value decreases.

The value increases, but the product of the two, that is,

But it remains roughly the same. According to the initial and boundary conditions of the problem, the solution u of the consolidation equation can be expressed by Fourier series.

The consolidation ratio and the time required for complete consolidation can be roughly calculated by the consolidation coefficient.

Extended data:

Determination method:

Indirect calculation method

Indirect calculation methods are represented by Wang Xiuyan method, neural network calculation method, residual settlement logarithm method, least square method, proportional series derivation algorithm, genetic algorithm, semi-logarithmic method of consolidation rate and trial and error method.

In essence, neural network calculation method, least square method and genetic algorithm can not be classified as methods to determine the consolidation coefficient, but only the mathematical processing methods of neural network calculation method, least square method and genetic algorithm are used in the process of determining the consolidation coefficient. Karl Terzaghi's one-dimensional consolidation equation is the most basic equation in the above indirect derivation algorithm.

The biggest advantage of indirect derivation algorithm is that it can effectively eliminate the influence of human factors in the calculation of consolidation coefficient and improve the speed of data processing and the calculation accuracy of data.

Inversion analysis method

The calculation methods of inversion analysis are represented by modified Asaoka method, measured settlement calculation algorithm and measured pore pressure calculation algorithm. According to the measured pore pressure or settlement in the construction site, the consolidation coefficient is calculated by inversion.

The calculation formula in the inversion analysis method still comes from Karl Terzaghi's one-dimensional consolidation theory formula. Because the inversion method can use the existing observation data of settlement or pore pressure to analyze and calculate the consolidation coefficient and other parameters of soft soil, it can better predict the later settlement development.

Therefore, the inversion analysis method has high engineering practical value. In the process of soft foundation treatment, the consolidation coefficient of soft soil is often inverted according to the actual monitoring data, so as to master the consolidation characteristics of soft soil more accurately, correct the design error and correctly judge the engineering effect.

Baidu encyclopedia-consolidation coefficient