CN103061320B - Method for determining soil permeability coefficient on basis of piezocone sounding - Google Patents

Abstract

The invention provides a method for determining soil permeability coefficient based on pore pressure static sounding, the steps are: first step, determine the depth and cone head radius of the pore pressure static sounding hole through the pore pressure static sounding report and the height of groundwater level at the site, and use the Robertson soil layer classification map to determine the division of soil layers; the second step is to obtain soil samples from different soil layers and conduct density tests to determine the weight of the soil layer; the third step is to determine the weight of the soil layer according to the first step and the second The parameters obtained in the first step determine the standard parameters of pore pressure static penetration testing, that is, the pore water pressure ratio and the standard cone resistance; the fourth step, determine the permeability coefficient index according to the standard parameters of pore pressure static penetration testing obtained in the third step; The fifth step is to determine the soil layer coefficient in the radial distribution of initial excess pore pressure according to the division of soil layers; the sixth step is to determine the soil permeability coefficient according to the results of the first to fifth steps above. The invention can accurately determine the permeability coefficient of the soil, and brings great convenience to the investigation and design of the permeability of the soil.

Description

Method for Determining Soil Permeability Coefficient Based on Pore Pressure Static Sounding

technical field

The invention relates to a method in the technical field of construction engineering, in particular to a method for determining soil permeability coefficient based on pore pressure static penetration testing.

Background technique

Soil permeability coefficient is an important parameter in geotechnical engineering design such as foundation pit dewatering design, foundation settlement estimation, and slope stability analysis. Accurately obtaining soil permeability coefficient has important engineering practical significance. The methods for determining soil permeability coefficient in engineering mainly include laboratory test and field test. There are many disadvantages in the indoor test: 1) The disturbance of the soil sample is large; 2) The field conditions cannot be accurately simulated; 3) The workload is heavy, the test time is long, and the cost is high. There is a large difference between the permeability coefficient measured in the laboratory test and the real value of the field soil, especially when there are many thin sand layers or weak interlayers in the foundation, the error is even greater. The current on-site test is complicated, the work area and workload are large, the time is long, and the cost is relatively high.

With the continuous development of in-situ testing technology, as a new type of in-situ testing technology, pore pressure static penetration testing technology has been widely used in engineering surveys, such as dividing soil layers, distinguishing soil types, and determining soil layer parameters. wait. Pore pressure static penetration testing, that is, pore water pressure static penetration testing, is to install water permeators and sensing elements for measuring pore water pressure on the probe of standard static penetration testing, and continuously measure the cone tip at the cone head The in-situ test has the advantages of low cost, good reliability, short exploration period, light equipment, and simple operation. At present, the method of determining the soil permeability coefficient by pore pressure static sounding is mainly empirical method and dissipation test. The former has strong regional characteristics, high uncertainty factors, and large deviations; the latter needs to be tested for different soil layers, which requires a lot of work, time-consuming, and high costs. Therefore, there is an urgent need for a method that can directly and accurately test the soil permeability coefficient by pore pressure static penetration test without dissipation test, which will bring great convenience to engineering investigation.

After searching the existing technical literature, it was found that "Permeability determination from on-the-fly piezocone sounding" was published in "Journal of Geotechnical and Geoenvironmental Engineering" (2005, Vol.131, No.5pp.643-653) by Elsworth et al. (Rapid determination of permeability based on pore pressure static penetration testing)" gives a semi-theoretical and semi-empirical determination method, but this method is only suitable for partially drained soil and sandy soil with good water permeability. Based on Elsworth's research, Chai et al. published "Estimating hydraulic conductivity from piezocone sounding" (calculation of permeability coefficient based on pore pressure static sounding) published in "Géotechnique" (2011, Vol.61, No.00pp.1-10) in 2011. " also gave a method to determine the permeability coefficient, but this method relies on experience and assumes that the initial excess pore pressure distribution function is applicable to a specific viscous formation, and the test results obtained are very different from those in my country, making it difficult to apply directly.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for determining the coefficient of soil permeability, determine the field soil layer division and related parameters through the pore pressure static penetration test report, and obtain the weight of the field soil according to the density test at the same time. , so as to determine the standard parameters and permeability coefficient index of pore pressure static penetration, determine the distribution coefficient of soil layer according to the division of soil layer, and finally determine the permeability coefficient of soil, thus bringing convenience to geotechnical investigation and design.

The present invention is achieved through the following technical solutions, comprising the following steps:

The first step is to determine the depth H of the piezostatic penetration hole, the radius a of the cone head and the relative groundwater level H _w through the piezostatic penetration test report, and use the Robertson soil layer classification diagram to determine the soil layer division.

The pore pressure static penetrator refers to: a standard pore pressure static penetration penetrator with a cone head angle of 60°, a bottom area of 1000 mm ² , and a side wall friction cylinder surface area of 15000 mm ² is used at 0.02 m/s The penetration speed is pressed into the soil, so as to test the cone tip resistance q _c , the side wall friction resistance f _s and the pore water pressure u _a .

The depth of the piezostatic sounding hole refers to the distance from the hole piezostatic sounding hole to the bottom of the hole.

The relative groundwater level refers to: the distance from the pore pressure static sounding hole to the groundwater level, when the groundwater level is below the pore pressure static sounding hole, the relative groundwater level is a negative value; When the static penetration is above the hole, the relative groundwater level is positive.

The Robertson soil layer classification diagram refers to: the soil layer classification diagram drawn with the friction ratio R _f (%) as the abscissa and the cone tip resistance _qc as the vertical coordinate. According to the test data, the foundation soil can be divided into different soil layers.

The friction ratio R _f refers to the ratio of the side wall friction f _s to the cone tip resistance q _c , expressed as a percentage.

The division of soil layers means that the foundation soil is layered, and different soil layers have different properties. The total number n of soil layers and the depth of each soil layer within the depth range of the piezostatic penetration hole are determined by soil layer division.

The second step is to obtain soil samples from different soil layers, conduct a density test, and determine the weight of the soil layer.

The acquisition of soil samples refers to: use a thin-walled soil extractor to obtain soil within the depth of the field test for indoor density testing. It is appropriate.

The density test refers to: the wet density of each soil layer is measured by the ring knife method and other density test methods, and the corresponding weight is calculated.

The weight of the soil satisfies the formula:

γ=ρg

Among them, γ is the weight of the soil, ρ is the wet density, and g is the acceleration of gravity, which is approximately 10m/s ² .

The third step is to determine the standard parameters of the piezostatic penetration test according to the depth, cone radius and relative groundwater level obtained in the first step and the soil layer weight parameter obtained in the second step, that is, the pore Water pressure ratio and standard cone resistance.

The pore water pressure ratio satisfies the formula:

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}$

Among them, B _q is the pore water pressure ratio, u _a is the pore water pressure, u _s is the initial static pore water pressure, q _c is the resistance of the cone tip, β is the corrected area ratio, 0.84, σ _v0 is the initial vertical total stress .

The initial static pore water pressure satisfies the formula:

u _s =γ _w h

Wherein, γ _w is the weight of water, approximately 10kN/m ³ . h is the depth of the soil below the water table.

The depth of the soil below the groundwater table satisfies the formula:

h=H+H _w

Among them, H is the depth of piezostatic penetration hole, which is obtained from the first step, and _Hw is the relative groundwater level, which is obtained from the first step.

The initial total vertical stress satisfies the formula:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

Among them, n is the total number of soil layers within the depth range of the piezostatic penetration hole, obtained from the first step, γ _i is the weight of the i-th layer of soil, obtained from the second step, h _i is the weight of the i-th layer of soil Depth, obtained from the first step.

The standard cone tip resistance satisfies the formula:

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

Among them, Q _t is the standard cone tip resistance, σ′ _v0 is the initial vertical effective stress.

The initial vertical effective stress refers to the vertical intergranular stress transmitted by the soil particles in the soil, which satisfies the formula:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}\mathrm{<span\; class="notranslate">\; h</span>}$

The fourth step is to determine the permeability coefficient index according to the standard parameters of pore piezostatic penetration testing obtained in the third step.

The permeability coefficient index satisfies the formula:

When B _q Q _t <0.45, $K_{\mathrm{D.}}=\frac{1}{B_q{Q}_t};$

When B _q Q _t ≥0.45, $K_{\mathrm{D.}}=\frac{0.044}{{\left(B_q{Q}_t\right)}^{4.91}}$

Among them, K _D is the permeability coefficient index, dimensionless, B _q is the pore water pressure ratio, Q _t is the standard cone tip resistance, B _q and Q _t are obtained from the third step.

The fifth step is to determine the soil layer coefficient α in the radial distribution of the initial excess pore pressure according to the soil layer division.

The radial distribution of the initial excess pore pressure refers to the radial distribution of the pore water pressure near the cone head before the excess pore water pressure dissipates when the cone head penetrates into the soil, satisfying the formula:

$\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}$

Among them, u is the pore water pressure at any point on the excess pore pressure distribution curve, u _s is the initial static pore water pressure, u _a is the pore water pressure, r is the distance from any point on the excess pore pressure distribution curve to the cone head, a is the cone radius.

The α refers to the soil layer coefficient, which is determined according to the division of soil layers. Specifically, it can be: 0.5 for clay; 0.3 for silty clay; 0.1 for silt; 0.05 for sandy silt; 0.01 for sandy soil.

The sixth step is to determine the soil permeability coefficient according to the results of the first step to the fifth step above.

The permeability coefficient of the soil refers to: a proportional coefficient reflecting the water permeability of the soil, which satisfies the formula:

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}\mathrm{<span\; class="notranslate">\; u</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}$

Among them, k is the permeability coefficient of the soil, U is the penetration velocity, and U is obtained from the first step.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention relies on dislocation theory, continuity theory and Darcy's law, comprehensively considers the impact of initial excess pore water pressure distribution characteristics on the calculation of hydraulic gradient on the surface of the cone head during static penetration of pore pressure, and avoids the predecessors relying on pure The empirical determination of the distribution characteristics of the initial excess pore water pressure results in the unreliability of the determination of the soil permeability coefficient. In practical application, the present invention has the advantages of simple method, short time consumption, low cost, less disturbance to the soil, and the ability to obtain the permeability coefficient continuously changing with the formation depth over the traditional method in practical application. Especially when there are many thin sand layers or weak interlayers in the ground, it is difficult to make indoor soil samples in the traditional method due to the limitation of on-site soil sampling. The present invention can continuously test the permeability coefficient of thin layers or weak interlayers. The invention is applicable to the problem of determining soil permeability coefficient by pore pressure static penetration testing.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the classification map of embodiment soil layer.

Fig. 2 is the soil layer division and test results in the hole pressure static penetration test report of the embodiment.

Fig. 3 is a comparison diagram of the soil permeability coefficient determined by the method of the embodiment, the test value and the standard value.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example:

In this embodiment, the method of determining the soil permeability coefficient of the pore pressure static sounding test is illustrated by the results of the pore pressure static sounding test. There are no operations specifically described in this embodiment, and the method given in the summary of the invention is used. I won't go into details here.

This embodiment is specifically as follows:

A pore pressure static sounding test site is located in Shanghai. According to the pore pressure static sounding test report, the pore pressure static sounding hole is located at the bottom of the Huangpu River, the groundwater level is 5.85m higher than the hole opening, and the hole depth is 35.7m. The radius of the cone head used in the pore pressure static penetration sounder is 0.02185m, and the penetration speed is 0.02m/s.

The first step is to determine the relevant parameters through the pore pressure static penetration test report, and use the Robertson soil layer classification diagram to determine the soil layer division.

First, according to the piezostatic penetration test report, the depth of the piezostatic penetration hole is 35.7m, the cone radius is 0.02185m, the penetration velocity is 0.02m/s, and the relative groundwater level is 5.85m.

Secondly, according to the pore pressure static penetration test report, the curve of the cone resistance _qc and the friction ratio R _f (%) can be obtained as a function of depth, as shown in Fig. 2, and the friction ratio R _f (% at any depth ) is the abscissa and the cone tip resistance q _c is the ordinate plotted in the Robertson soil layer classification map, see Figure 1, according to the different soil areas where the points are located in the Robertson soil layer classification map, the field soil can be The body is divided into five layers from top to bottom according to the depth: the first layer (0.0-5.51m) is a muddy clay layer; the second layer (5.51-15.03m) is a muddy silty clay layer; the third layer (15.03- 29.54m) is a gray silty clay layer; the fourth layer (29.54-32.32m) is a dark green silty clay layer; the fifth layer (32.32-35.71m) is a sandy silt layer, see Figure 2.

The second step is to obtain soil samples from different soil layers, conduct a density test, and determine the weight of the soil layer.

Use a thin-walled soil fetcher to take soil within the depth range of each soil layer on site. According to the ring knife method density test method, the density of the first layer of soil is 1.73g/cm ³ , then the weight of this layer is

γ=ρg=1.73×10=17.3kN/m ³

By analogy, the density of the second layer of soil is 1.78g/cm ³ , and its weight is 17.8kN/m ³ ; the density of the third layer of soil is 1.78g/cm ³ , and its weight is 17.8kN/m ³ ; the fourth layer of soil The density of the soil is 2.02g/cm ³ and the weight is 20.2kN/m ³ ; the density of the fifth layer soil is 1.96g/cm ³ and the weight is 19.6kN/m ³ .

The third step is to determine the standard parameters of piezostatic penetration testing.

Take the depth of 10m as an example to illustrate the calculation process at any depth:

From the first step and the second step, there are two soil layers within the depth range of 10m: 0.0~5.51m is the muddy clay layer with a weight of 17.3KN/m ³ ; 5.51~10m is the muddy silty clay layer with a weight of 17.8kN/m ³ , pore water pressure u _a at 10m is 0.37831MPa, cone tip resistance q _c is 0.60177MPa, soil depth h below groundwater level is 15.85m, then at 10m depth

The initial static pore water pressure u _s is

u _s =γ _w h=10×15.85=0.1585MPa

The total initial vertical stress σ _v0 is

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 5.85</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 17.3</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 5.51</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 17.8</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 5.51</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.23375</span>}\mathrm{<span\; class="notranslate">\; MPa</span>}$

The initial vertical effective stress σ′ _v0 is

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.23375</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.1585</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.07525</span>}\mathrm{<span\; class="notranslate">\; MPa</span>}$

The pore water pressure ratio B _q is

${\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.37831</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.1585</span>}}{\mathrm{<span\; class="notranslate">\; 0.60177</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.37831</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.84</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.23375</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.512916</span>}$

The standard cone tip resistance Q _t is

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.60177</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.37831</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.84</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.23375</span>}}{\mathrm{<span\; class="notranslate">\; 0.07525</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 5.695011</span>}$

The fourth step is to determine the permeability coefficient index.

from the third step

B _q Q _t =0.512916×5.695011=2.921062>0.45

Then the permeability index K _D is

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.044</span>}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4.91</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.044</span>}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2.921062</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4.91</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.28</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}}$

The fifth step is to determine the soil layer coefficient α in the radial distribution of the initial excess pore pressure according to the soil layer division.

Take the depth of 10m as an example to illustrate the calculation process at any depth:

From the first step, the 10m place is muddy silty clay, so the soil layer coefficient α in the radial distribution of the initial excess pore pressure at 10m is taken as 0.3.

The sixth step is to determine the permeability coefficient of the soil.

Take the depth of 10m as an example to illustrate the determination process of the permeability coefficient at any depth:

From the first step, the radius of the cone head is 0.02185m, and the penetration velocity is 0.02m/s, so the permeability coefficient of the soil at a depth of 10m is

$\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}{\mathrm{<span\; class="notranslate">\; UK</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.02185</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.02</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 2.28</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.3</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.07525</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.2068</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 8</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}$

As shown in Figure 3, the comparison chart of the soil permeability coefficient determined by the embodiment of the present invention and the test value and the standard value, it can be seen that the present embodiment can determine the permeability coefficient of the soil more accurately, compared with the previous method, It is more accurate and brings great convenience to the investigation and design of soil permeability.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (8)

1., based on a method for hole pressure touching methods determination soil body osmotic coefficient, it is characterized in that comprising the following steps:

The first step, determine depth H, the conehead radius a and relative groundwater table H in hole pressure touching methods hole by hole pressure touching methods report _w, and with Robertson soil layer classification chart determination compartmentalize soil;

Second step, from different soil obtain soil sample, carry out density test, determine soil layer severe;

The canonical parameter of the soil layer severe parameter determination hole pressure touching methods that the 3rd step, the degree of depth in hole pressure touching methods hole obtained according to the first step, conehead radius obtain with relative groundwater table and second step, namely pore water pressure compares B _qwith standard static point resistance Q _t;

4th step, the canonical parameter determination transmission coefficient index of hole pressure touching methods obtained according to the 3rd step;

Described transmission coefficient index meets formula:

Work as B _qq _tduring <0.45,

Work as B _qq _twhen>=0.45,

Wherein, K _dtransmission coefficient index, dimensionless, B _qpore water pressure ratio, Q _tstandard static point resistance, B _qand Q _tobtained by the 3rd step;

5th step, determine initially to surpass soil layer factor alpha in the pressure radial distribution of hole according to compartmentalize soil;

Described initial super hole pressure radial distribution refers to: during the conehead injection soil body, the radial distribution of pore water pressure near the conehead before excess pore water pressure not yet dissipates, meets formula:

Wherein, u is the pore water pressure of any point on this super hole pressure distribution curve, u _srest pore water pressure, u _abe pore water pressure, r is that on this super hole pressure distribution curve, any point is apart from the distance of conehead, and a is conehead radius; Described α refers to soil layer coefficient, determines according to compartmentalize soil:

6th step, according to the result of the above-mentioned first step to the 5th step, determine soil transmission coefficient;

The transmission coefficient of described soil refers to: the factor of proportionality of the water permeability of reflection soil, meets formula:

Wherein, k is the transmission coefficient of soil, and a is conehead radius, γ _wbe the severe of water, U is the penetrating speed of hole pressure touching methods penetrometer in first step hole pressure touching methods, K _dbe transmission coefficient index, α is soil layer coefficient, σ ' _v0it is initial vertical effective stress.

2. the method based on hole pressure touching methods determination soil body osmotic coefficient according to claim 1, is characterized in that, in the first step, described hole pressure touching methods refers to: be 60 ° by conehead angle, floor space is 1000mm ², sidewall friction cylinder surface area is 15000mm ²the hole pressure touching methods penetrometer of standard with in the penetrating speed of the 0.02m/s press-in soil body, thus test static point resistance q _c, side friction power f _swith pore water pressure u _a.

3. the method based on hole pressure touching methods determination soil body osmotic coefficient according to claim 1, is characterized in that, in the first step, described Robertson soil layer classification chart refers to: with frictional ratio R _f(%) be abscissa, static point resistance q _cfor the soil layer classification chart that vertical seat plots, according to test data, foundation soil is divided into different soil layers by this figure.

4. the method based on hole pressure touching methods determination soil body osmotic coefficient according to claim 1, it is characterized in that, in second step, described acquisition soil sample refers to: with thin-wall sampler, fetch earth within the scope of MTD at the scene, for doing indoor density test, the amount of fetching earth is determined according to test specimen amount, and every layer of soil is no less than three test specimens.

5. the method based on hole pressure touching methods determination soil body osmotic coefficient according to any one of claim 1-4, is characterized in that, in the 3rd step, described pore water pressure ratio meets formula:

Wherein, B _qpore water pressure ratio, u _apore water pressure, u _srest pore water pressure, q _cbe static point resistance, β is correction area ratio, gets 0.84, σ _v0it is initial vertical total stress;

Described rest pore water pressure meets formula:

u _s=γ _wh

Wherein, γ _wbe the severe of water, h is the degree of depth of the following soil body of groundwater table;

Described initial vertical total stress meets formula:

Wherein, n is the soil layer sum within the scope of depth of penetration, is obtained by the first step; γ _ibe i-th layer of native severe, obtained by second step; h _ibe i-th layer of native degree of depth, obtained by the first step.

6. the method based on hole pressure touching methods determination soil body osmotic coefficient according to claim 5, is characterized in that, described standard static point resistance meets formula:

Wherein, Q _tstandard static point resistance, σ ' _v0it is initial vertical effective stress.

7. the method based on hole pressure touching methods determination soil body osmotic coefficient according to claim 6, is characterized in that, described initial vertical effective stress refers to: the vertical intergranular stress that in the soil body, soil particle transmits, meets formula:

8. the method based on hole pressure touching methods determination soil body osmotic coefficient according to any one of claim 1-4, is characterized in that, in the 5th step, described α refers to soil layer coefficient, is specially: clay gets 0.5, and silty clay gets 0.3, silt gets 0.1, and sandy silt gets 0.05, and sand gets 0.01.