SU1631360A1 - Method for measuring the moisture content and density of soll samples in a sampler - Google Patents

Abstract

This invention relates to radioisotope methods for determining soil sediment properties. The purpose of the invention is to increase accuracy. The method includes placing a source and a gamma radiation detector at a fixed distance measuring the detector signal when gamma radiation passes through the air, through the walls of the reference sampler with known internal diameter and double wall thickness values, through the reference sampler filled with water, through the reference sample sampler filled with dry soil c. known porosity and mineral density, through the walls of the sampler with a known external diameter, through the sampler with the test soil and the determination of humidity and density from the measurement results. 6 Il.

Description

The invention relates to methods for analyzing materials by determining their density and is intended for use in determining the moisture content and density of soil-bottom sediment samples collected by column samplers during geotechnical surveys.

The purpose of the invention is to improve accuracy.

Fig. 1 shows a circuit for measuring the detector signal by passing gamma radiation through the air; in fig. 2 is a diagram of measuring the signal of the detector rii with the passage of gamma radiation through the air and the walls of the reference sampler with nominal values of internal diameter do and double wall thickness ho; in fig. 3 is a diagram for obtaining a PV detector signal for a reference sampler filled with water; in fig. 4 shows a scheme for obtaining a signal from a PCS detector when gamma radiation passes through a reference sampler filled with dry soil with a known porosity N and mineral density / Emin; in fig. 5 is a diagram of obtaining the signal of detector P2 when gamma radiation passes through the walls of the sampler with an outer diameter di; in fig. 6 is a diagram of the detection of the detector signal p when gamma radiation passes through a sampler filled with a sample of the soil under study.

ABOUT

05

s

When a sampling probe is examined by a gamma-ray beam at a test point of a completely water-saturated soil sample, for which the outer diameter of the sampler is measured di and the double wall thickness of the sampler hi and the inner diameter of the sampler are unknown, the expression

- skrskOvn-vrv vn - / "strstM P Pov

0)

where is the detector counting rate when gamma radiation passes from the source to the detector through the air;

, Dsc is the mass absorption coefficient of the soil skeleton;

rivers - the density of the soil skeleton;

IAQ is the mass absorption coefficient of water;

Ditch water density

W is the soil moisture content;

St is the mass absorption coefficient of steel;

PCT - steel density.

With the control determination of the count rate P2 with an empty column sampler at the point of the study of soil properties, the following expressions are valid

- / meet 1

P2 gt0e; (2)

2

By

- / "prsti

(3)

 1p (Po / P2) pstr

Substituting (3) into (1) gives the expression

 (/ MSKR + fi BP b w) dBH

P2e. (five)

Therefore, the definition of the reference reading P2 for a hollow sampler excludes from the expression (1) the variable value hi, i.e. thus, the effect of changing the double thickness of the steel wall from the nominal value can be taken into account.

When the reference, hollow steel cylinder is scanned with nominal values of double thickness of steel wall ho, internal diameter do and determination of counting rate hp, the following expressions are valid:

ni p0e; (6)

 In (Pr / Sch) / Years PCT

The unknown double wall thickness of the sampler hi can be found with y (er (4) and (7) from the expression hi

hi h0ho

: ri0ln (n0 / ri2) / ln (By / um). (eight)

The unknown internal diameter of the sampler dBH in expression (5) can be determined by the known values of do, di, ho, no, ni and pa by expressions

d.H d ,,.: m

dBH

 d0

do

. . di - h0ln (no / pa) / ln (n0 / ni) - do2-

do

(YU)

Taking into account (5) and (10) receive the following expression

do

di - П01п По / П2) Лп (По / П1) - (// skrsk + / UBPB W) do

In

P2

(eleven)

In the control readings of PB and PSC on a standard steel cylinder filled respectively with water with density p in or dry soil with known porosity N and mineral density rmin, taking into account (6) the expressions

, MBpBdo ln (ni / nB); (12)

and p L - ln ()

D SKRMIN Oo -, (K |

(13)

35

For a fully saturated soil, the expression

(1 -W). (14)

Solving equations (11), (12), (13), (14) with respect to W, yields

do n i In (p1 / psk)

1 -N

40 sh

01

 h 1n (n0 / n2) ° ln (n0 / ni)

I n 1 In- + P2

45 45 5Q,

In (m / ncic j, ni 1-Nln i

(15)

The density p of the fully saturated soil under investigation is determined by the following expression

.ABOUT

where y is a coefficient of 0.08 or 0.11 for a wide or narrow beam of gamma radiation, respectively.

Expression (16), taking into account (11) and (13), can be

RMIN (1 -N), u1P -

.l - ° (n2 / po) n.

d1

-ywpB.

In (ni / psk)

In (Fri / Pr)

(17)

The method eliminates the error due to the presence of a steel wall, variations in wall thickness and column diameter of the soil sample in the sampler. Thus, when performing one-time easy-to-use additional reference readings, the accuracy of determining the moisture content and density of the soil sample in the column sampler is high during the process of multiple soil sampling during geotechnical tests.

FIG. 1-6 show an embodiment of a specific implementation of the method using a column device that includes a housing 1 with a guide roller 2, a protective lead container 3 for mounting a Co or 137Cs radiation source 4 and a gamma radiation detector 5 located in the housing 1 opposite the source 4 at a constant distance from it, allowing for the placement of a core sampler 6 with a sample 7 of the soil under study between the source 4 and the detector 5.

Before measuring the properties of soil samples in the column sampler, the following control measurements are made: determination of the count rate for the passage of gamma radiation in the air; determining the count rate m when passing gamma radiation through a hollow cylinder with nominal values of do and ho; determination of the pv count rate during the passage of gamma radiation through a steel cylinder with nominal values of do and ho filled with water; determination of the Peck's counting rate during the passage of gamma radiation through a steel cylinder with nominal values of ho and dryly salted with a well-known porosity N and a mineral density of / min. measurements of the external diameter of the core sampler along its length with dn no dim and at the same points the test counts from P21 to P2t along the empty sampler. ,

After the control measurements are made in the process of sampling, the counting speed n is determined along the length of the core sampler with a soil break at the points of determination of dn - dim and gsh - pat.

The values of humidity and density of the soil sample are determined for each sample n at the points of determination of di and P2 along the length

von sampler for the ratio-. m (15) and (17) respectively.

Claims (1)

The invention The method for determining the moisture content and density of a soil sample in a hollow cylinder-shaped sampler, including placing the source and detector of gamma radiation at a fixed distance, measuring the magnitude of the detector signal as the gamma radiation passes through the air into the gap between the source and the detector, measuring the magnitude of the detector signal p when gamma radiation passes through a sampler filled with soil breakdown and the determination of humidity W and density p, characterized in that, in order to increase Accuracy, before measuring the magnitude of the detector signal p, the magnitude of the detector signal ni when gamma radiation passes through the walls of the reference sampler with nominal values of internal diameter do and double wall thickness ho is additionally determined, the magnitude of the PV signal of the detector when passing gamma radiation through the reference a sampler filled with water having a known density p v determines the magnitude of the Peck signal of the detector when gamma radiation passes through a reference sampler filled with A soil sampler with a known porosity N and mineral density of PMIN is placed in the gap between the source and the detector, the sampler is fixed, its position is measured, the external diameter di of the sampler is measured along the axis connecting the center of the source and detector, and the gamma signal radiation through the walls of the sampler, where the measurement of the magnitude of the detector signal n is carried out in a fixed position of the sampler, and the determination of humidity and density is made by the ratio do, n j 1n (p1 / psk) W di-ho4no /; 2) In (no / Hi Inc2 +1 -N In (Fri / Psk). ni Inp - Pmin (1 In (P1 / PSC) 01 -yWpQ, 1 -No to N) dpln (n2 / n} n0ln (r.2 / ng) In (ni / n0) where y is a coefficient taking values of 0.08 or 0.11 for a wide and narrow beam of gamma radiation, respectively. J 1 ig.2 FIG. five