CN101575846A - Technique and method for geotechnical engineering investigation and sampling based on soil variability - Google Patents

Abstract

The invention provides a technique and a method for geotechnical engineering investigation and sampling based on soil variability, which is characterized in that the technique and the method are implemented by establishing quantized soil variability databases and calculating vertical correlation distance, horizontal correlation distance and variability coefficients of soil; main implementation steps are as follows: (1) establishing a quantifiable soil variability database based on investigation and sampling data of neighboring regions, including the species, thickness and standard penetration test SPT-N values of soil layers; (2) utilizing the SPT-N value of each soil layer to plot a trend line changing along depth and dividing different soil layers in broken positions; (3) calculating the vertical correlation distance and the horizontal correlation distance of each soil mass and estimating the optimum vertical interval and horizontal exploration drilling interval of engineering investigation and sampling; and (4) calculating the variability coefficient of each soil mass in order to determine the minimum amount of test samples and exploration drilling. The technique and the method have the advantages of providing a quantification method taking soil variability into consideration, systematically and reliably designing geotechnical engineering investigation and sampling and using obtained data to design economical and safe foundations.

Description

A kind of geotechnical investigation and Sampling techniques and method based on soil variability

Technical field

The invention belongs to the geotechnical engineering technical field, a kind of geotechnical investigation and Sampling techniques based on soil variability are provided, mainly utilize probabilistic method to quantize the intrinsic variability of the soil body, thereby geotechnical investigation and level interval vertical after the decision with the optimization of sampling, total prospecting and number of samples and total testing bore holes amount.

Technical background

Geotechnical investigation is the step that all construction works must will be done with sampling, its resulting data, sample and test result all are used for the foundation of design building engineering, but at present so the geotechnical investigation and the Sampling techniques that have still lack unification, effectively, the method of reliable and standard, so can not know for certain whether the scope of required prospecting and sampling and quantity is representative, resulting data are unnecessary sometimes, also be not enough sometimes, its main cause is that existing method is not consider the variability of the soil body, therefore with the existing prospecting and the method for sampling, except meeting waste ample resources, whether safety is safe can't to affirm designed foundation.The present invention has made full use of prospecting and sampled data resource in the past, set up a kind of new method based on probability theory and quantize the intrinsic variability of the soil body, the technology that can optimize geotechnical investigation and sampling is provided, the data that obtain can be representative, the cost of engineering investigation and sampling be can reduce greatly, safety and reliable design just can be obtained later foundation.Because China is in period busy at putting up installations, large-scale construction project constantly increases, and building construction types becomes increasingly complex, safe and economic foundation designing requirement is more and more higher, a real left side is necessary to adopt new prospecting and Sampling techniques to fall the end cost while also to reach more rigorous designing requirement, so the present invention has huge market potential;

Summary of the invention

The object of the present invention is to provide a kind of geotechnical investigation and Sampling techniques, to remedy the deficiency that existing geotechnical investigation and Sampling techniques lack unified, effective, reliable and standard method based on soil variability.

In order to realize the foregoing invention purpose, the technical scheme of employing is as follows:

The objective of the invention is at having the problem that geotechnical investigation and Sampling techniques still lack unified, effective, reliable and standard method now, geotechnical investigation and Sampling techniques based on soil variability are provided, so that can provide system and rational plan to geotechnical investigation and sampling, thereby obtain representative and prospecting and sampled data reliability, provide safety safe design later construction work ground foundation.

In order to realize the foregoing invention purpose, the technical scheme of employing is as follows:

A kind of geotechnical investigation and Sampling techniques based on soil variability, realize as follows:

Prospecting and sampled data based on the neighbouring area, set up one and can be used to quantize the soil variability database, draw the trend line chart that changes along soil depth by the SPT-N value of utilizing each soil layer, in each Trendline broken positions, the corresponding line of demarcation that marks off different soil.Based on the line of demarcation of different soil, quantize soil variability, find out the vertical correlation distance of representing each soil layer; Based on all SPT testing bore holes in the vertical interval database of prospecting and sampling, calculate the average of the vertical correlation distance in each soil layer; Engineering investigation is worth greater than this with the optimization vertical interval of sampling in similar soil layer after the order; And find out the horizontal correlation distance of representing each soil layer based on database, and engineering investigation calculates the coefficient of variation of wanting to answer soil layer with the level of optimization spacing of sampling in similar soil layer greater than horizontal correlation distance and based on the SPT-N value of different soil after the order, by minimum prospecting and the drilling hole amount of sampling of needing of the coefficient of variation computational engineering that utilizes different soil, realize optimizing geotechnical investigation and Sampling techniques.

Advantage of the present invention provides a quantization method of considering soil variability, and system and Design in Reliability are provided in later geotechnical investigation and sampling, and resultant representational data can be used for designing foundation economic and that safety is safe.

Description of drawings

Accompanying drawing 1 is the division of different statistical nature soil layers.

Accompanying drawing 2 converts steady data to for after certain soil layer cancellation Trendline.

Accompanying drawing 3 is the level of optimization spacing of later engineering investigation and sampling.

Accompanying drawing 4 is for need estimating prospecting hits scale.

The specific embodiment

The present invention is described further below in conjunction with accompanying drawing.

The present invention includes following steps:

(1), sets up one and can be used to quantize the soil variability database, comprising the standard penetration test SPT-N value of different soil kind, each the thickness of the layer and each soil layer based on the prospecting and the sampled data of neighbouring area.

(2) draw the trend line chart that changes along soil depth by the SPT-N value of utilizing each soil layer, in each Trendline broken positions, the corresponding line of demarcation that marks off different soil, as shown in Figure 1.

(3) based on the line of demarcation of described database of step (1) and the described different soil of step (2), quantize soil variability, find out the vertical correlation distance of representing each soil layer, by formula ${\mathrm{\δ}}_Z=\frac{1}{A}\underset{a=1}{\overset{A}{\mathrm{\Σ}}}\left({{\mathrm{\Γ}}_a}^2\mathrm{a\ΔZ}\right)$ Determine vertical correlation distance δ z, as shown in Figure 2, Γ wherein _a ²Be the variance reduction coefficient, based on the spatial mean value variance of SPT-N value along depth direction

With the some variance of SPT-N value at whole soil layer

By formula ${{\mathrm{\&Gamma;}}_a}^2=\frac{{{\tilde{N}}_a}^2}{{{\tilde{N}}_{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="A20091003809300111.png,A20091003809300141.png"\; state="\{\{state\}\}">V</figure-callout>}}}^2}$ Determine that A is the total quantity of SPT-N value in a certain boring, Δ Z is a spacing between points, and a represents a pair of SPT-N value.

(4), calculate the average δ of the vertical correlation distance in each soil layer based on vertical interval and interior all the SPT testing bore holes of the described database of step (1) of described prospecting of step (3) and sampling _v, make later engineering investigation and sample in the optimization vertical interval D 〉=δ of similar soil layer _v, as shown in Figure 3.

(5) find out the horizontal correlation distance of representing each soil layer based on the described database of step (1), by formula ${\mathrm{\&delta;}}_H=\frac{1}{B}\underset{b=2}{\overset{B}{\mathrm{\&Sigma;}}}\left({{\mathrm{\&Gamma;}}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="A20091003809300111.png,A20091003809300141.png"\; state="\{\{state\}\}">b</figure-callout>}}}^2\mathrm{b\&Delta;h}\right)$ Determine horizontal correlation distance δ _H, Γ wherein _b ²Be the variance reduction coefficient, based on the spatial mean value variance of SPT-N value along continuous straight runs

With the some variance of SPT-N value at along continuous straight runs

By formula ${{\mathrm{\&Gamma;}}_{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="A20091003809300111.png,A20091003809300141.png"\; state="\{\{state\}\}">b</figure-callout>}}}^2=\frac{{{\tilde{N}}_b}^2}{{{\tilde{N}}_{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="A20091003809300111.png,A20091003809300141.png"\; state="\{\{state\}\}">H</figure-callout>}}}^2}$ Determine that B is the total quantity of a certain group of SPT-N value along continuous straight runs, Δ h is a spacing between points, and b represents the SPT-N value of a pair of along continuous straight runs.

(6) in each exploratory bore-hole to some the thickness of the layer Ti, calculate the average δ vi of the vertical correlation distance of this soil layer, should be divided into the k layer every δ vi by soil layer mutually, k=Ti ÷ δ vi wherein, SPT-N value on each layer horizontal plane is formed many group straight line ordered series of numbers, S1, S2 ... .Si, each ordered series of numbers is all calculated corresponding horizontal correlation distance δ _Hi, get its average δ at last _h, and make later engineering investigation and sample in the level of optimization spacing 〉=δ of similar soil layer _Hi, as shown in Figure 3.

(7) by formula $V=\frac{\tilde{N}}{\stackrel{\&OverBar;}{N}}$ Definitive variation coefficient V, a logical given worst error value Δ of accepting _rWith probable value α, by formula $\mathrm{\&tau;}=\frac{t_{\mathrm{\&alpha;}}}{\sqrt{n}}<\frac{{\mathrm{\&Delta;}}_r}{V}$ With the minimum prospecting number of samples n that needs of definite whole engineering shown in the accompanying drawing 4, wherein

With N be respectively the standard deviation of the total SPT-N value of a certain soil layer and average, t _αIt is the functional value that student ' s t distributes in the statistics.

(8), follow according to minimum minimum prospecting and the sampling hole quantity Q of needing of prospecting number of samples n Q=n ÷ (Ti ÷ δ z) calculating by formula that need of the determined whole engineering of step (7) to a certain soil layer corresponding thickness Ti.

(9), calculate a plurality of average level correlation distance δ for its respective thickness of other soil layer Ti _Hi, get δ _HiMaximum value be that horizontal exploratory bore-hole is apart from U, as shown in Figure 3.

Case study on implementation:

Present embodiment is applied in COTAI location, Macao construction airport installation, large-scale hotel, sports center and road event with a kind of geotechnical investigation and Sampling techniques based on soil variability.Application process is as follows:

1, according to engineering unit, consultant firm, the passing geotechnical investigation data in the Macao district that university and portion of government provide, the soil layer of this area is respectively 24 meters thick argillic horizons and 22 meters thick sandy soil layers, sets up the geotechnical investigation database;

2, calculate optimization prospecting and sampling skill spacing, concrete steps are as follows:

Calculate the vertical and horizontal correlation distance of argillic horizon and sandy soil layer:

Clay: vertical correlation distance=1.07 meter, horizontal correlation distance=130

Sandy soil: vertical correlation distance=0.99 meter, horizontal correlation distance=125

And specify vertical and level prospecting and sampling interval difference 〉=vertical correlation distance and horizontal correlation distance; So the prospecting of clay and sampling interval can be decided to be=and 1.5 meters; The prospecting of sandy soil and sampling interval can be decided to be=and 1 meter

Designated horizontal direction prospecting and sampling interval=130 meter.

3, determine minimum number of samples, concrete steps are as follows:

Argillic horizon: the data computation of accessory rights requirement 1 goes out the coefficient of variation V=0.46 of argillic horizon, and appointment can be accepted worst error and count Δ _r=10%, probable value α=95%; $\frac{{\mathrm{\&Delta;}}_r}{V}=0.286,$ From table 1, with τ ₉₅=0.286, draw minimum number of samples n=35;

The sandy soil layer: from 1, data computation go out the coefficient of variation V=0.57 of argillic horizon, appointment can be accepted worst error and count Δ _r=10%, probable value α=95%; $\frac{{\mathrm{\&Delta;}}_r}{V}=0.175,$ From table 1, with τ ₉₅=0.175, draw minimum number of samples n=55;

4, decision is minimum need reconnoitre and sampling hole:

(1) clay:

Each boring maximum can be reconnoitred with hits and is:

Vertical prospecting of the thickness ÷ of argillic horizon and sampling interval: TL1 ÷ DL1=20 ÷ 1.5=13

So needed boring is:

Always each boring maximum of prospecting that needs and hits ÷ can be reconnoitred and hits=35 ÷ 13=3

(2) sandy soil:

Each boring maximum can be reconnoitred with hits and is:

Vertical prospecting of husky the thickness of the layer ÷ and sampling interval: TL2 ÷ DL2=22 ÷ 1.0=22

So needed boring is:

Always each boring maximum of prospecting that needs and hits ÷ can be reconnoitred and hits=90 ÷ 22=5.

Claims (14)

1, a kind of geotechnical investigation and Sampling techniques and method based on soil variability, it is characterized in that: by setting up a database that is used for quantizing soil variability, calculate the vertical correlation distance of the soil body, calculate the horizontal correlation distance of the soil body and the coefficient of variability of the soil body and realize.

2, a database that is used for quantizing soil variability according to claim 1 is characterized in that: based on the foundation of the prospecting data of neighbouring area, comprised the distribution and the thickness of soil layer, the kind of the soil body, the SPT-N value of standard penetration test.

3, vertical correlation distance according to claim 1 is characterized in that: utilize vertical correlation distance to decide prospecting and the vertical interval of sampling.

4, horizontal correlation distance according to claim 1 is characterized in that: utilize horizontal correlation distance to decide prospecting and the level interval of sampling.

5, the coefficient of variation according to claim 1 is characterized in that: with deciding prospecting minimal number and the exploratory bore-hole required minimal number required with sampling.

6, SPT-N value according to claim 2 is characterized in that: draw the trend line chart that changes along soil depth by the SPT-N value of utilizing each soil layer, and in each Trendline broken positions, the corresponding line of demarcation that marks off different soil.

7, the vertical interval of prospecting according to claim 3 and sampling is characterized in that: by formula ${\mathrm{\&delta;}}_Z=\frac{1}{A}\underset{a=1}{\overset{A}{\mathrm{\&Sigma;}}}\left({{\mathrm{\&Gamma;}}_a}^2\mathrm{a\&Delta;Z}\right)$ Determine vertical correlation distance δ z, wherein Γ _a ²Be the variance reduction coefficient, based on the spatial mean value variance of SPT-N value along depth direction

With the some variance of SPT-N value at whole soil layer

By formula ${{\mathrm{\&Gamma;}}_a}^2=\frac{{{\tilde{N}}_a}^2}{{{\tilde{N}}_V}^2}$ Determine that A is the total quantity of SPT-N value in a certain boring, Δ Z is a spacing between points, and a represents a pair of SPT-N value.

8, the level interval of prospecting according to claim 4 and sampling is characterized in that: by formula ${\mathrm{\&delta;}}_H=\frac{1}{B}\underset{b=2}{\overset{B}{\mathrm{\&Sigma;}}}\left({{\mathrm{\&Gamma;}}_b}^2\mathrm{b\&Delta;h}\right)$ Determine horizontal correlation distance δ _H, Γ wherein _b ²Be the variance reduction coefficient, based on the spatial mean value variance of SPT-N value along continuous straight runs

With the some variance of SPT-N value at along continuous straight runs

By formula ${{\mathrm{\&Gamma;}}_b}^2=\frac{{{\tilde{N}}_b}^2}{{{\tilde{N}}_H}^2}$ Determine that B is the total quantity of a certain group of SPT-N value along continuous straight runs, Δ h is a spacing between points, and b represents the SPT-N value of a pair of along continuous straight runs.

9, prospecting according to claim 5 minimal number and the exploratory bore-hole required minimal number required with sampling is characterized in that: by formula $V=\frac{\tilde{N}}{\stackrel{\&OverBar;}{N}}$ Definitive variation coefficient V, a logical given worst error value Δ of accepting _rWith probable value α, by formula $\mathrm{\&tau;}=\frac{t_{\mathrm{\&alpha;}}}{\sqrt{n}}<\frac{{\mathrm{\&Delta;}}_r}{V}$ Determine the minimum prospecting number of samples n that needs of whole engineering, wherein With N be respectively the standard deviation of the total SPT-N value of a certain soil layer and average, t _αIt is the functional value that student ' st distributes in the statistics.

10, the vertical interval of prospecting according to claim 7 and sampling is characterized in that:

Based on all SPT testing bore holes in the database, calculate the average δ of the vertical correlation distance in each soil layer _v, make the back engineering investigation and sample in the optimization vertical interval D 〉=δ of similar soil layer _v

11, the average δ of the vertical correlation distance in the described a certain soil layer of the horizontal correlation distance of prospecting according to claim 8 and sampling and claim 10 _Vi, it is characterized in that:

In each exploratory bore-hole to some the thickness of the layer T _i, calculate the average δ vi of the vertical correlation distance of this soil layer, should be divided into k layer, wherein k=T every δ vi by soil layer mutually _i÷ δ vi forms many group straight line ordered series of numbers, S to the SPT-N value on each layer horizontal plane ₁, S ₂... .S _i, each ordered series of numbers is all calculated corresponding horizontal correlation distance δ _Hi, get its average δ at last _h, and make the back engineering investigation and sample in the level of optimization spacing 〉=δ of similar soil layer _Hi

12, the minimum prospecting number of samples n that needs of definite whole engineering according to claim 9 is characterized in that: to a certain soil layer corresponding thickness T _i, Q=n ÷ (T by formula _i÷ δ z) calculates minimum prospecting and the sampling hole quantity Q of needing.

13, the horizontal correlation distance average δ of a certain soil layer according to claim 11 _h, it is characterized in that: for its respective thickness of other soil layer T _i, all calculate a plurality of average level correlation distance δ _Hi, get δ _HiMaximum value be that horizontal exploratory bore-hole is apart from U.

14, according to claim 1～13 described a kind of geotechnical investigation and Sampling techniques and method, it is characterized in that: the q that can be applicable to cone penetration test CPT with quadrat method based on soil variability _cValue.

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