CN201635064U - Resistivity static penetration probe - Google Patents

Abstract

The utility model discloses a resistivity static penetrating probe. Two annular electrodes (2) are wrapped around the upper half of the probe, and insulating layers (1) are formed on both sides of the annular electrodes (2); The lower half of the probe is provided with a three-component geophone (3), and an inclinometer (4) is arranged at the bottom of the three-component geophone (3), and the friction cylinder (5) is located below the inclinometer (4). A pore water pressure sensor (6) is provided in the middle of the friction cylinder (5), a probe (7) is connected below the friction cylinder (5), and a pore pressure filter ring (8) is located between the friction cylinder (5) and the probe (7). ) at the junction. The use of this probe has the characteristics of in-situ, rapidity, accuracy, and economy, and provides a powerful detection tool for the practice of civil engineering foundation treatment.

Description

Resistivity static penetration probe

technical field

The utility model relates to a resistivity static sounding probe, which belongs to a static sounding device capable of continuously analyzing and testing the in-situ resistivity of soil layers in the field of geotechnical engineering.

Background technique

Static CPT technology refers to using a pressure device to press a penetrating rod with a probe into the test soil layer, and through the measurement system to test the cone tip resistance and side wall friction resistance of the soil, some basic physical properties of the soil can be determined. Mechanical properties, such as the deformation modulus of the soil, the allowable bearing capacity of the soil, etc. The static penetration technology has a history of more than 80 years. Static CPT is widely used in the world, partially or completely replacing drilling and sampling in engineering investigation. In 1965, our country first successfully developed the electric measuring type static penetration and applied it to the survey. In recent years, with the rapid development of sensor technology, many new CPT technologies have emerged, which can quickly and accurately obtain pore water pressure, seismic waves, pollutant properties, temperature, and even images of soil layers. It has been widely used in the field of environmental geotechnical engineering in foreign countries. The research on the new static CPT sensor started relatively late in my country. The static CPT of single and double bridges widely used in China can only test the penetration resistance or specific penetration resistance, side wall friction resistance, and the basic soil layer that can be determined. Physicomechanical properties are very limited.

Contents of the invention

Technical problem: The technical problem to be solved by this utility model is to propose a resistivity static penetration probe for foundation treatment effect detection in view of the defects existing in domestic single-double bridge static detection technology.

Technical solution: The outer circumference of the upper half of the resistivity static penetration probe of the utility model is covered with two ring electrodes, and the upper and lower sides of the ring electrodes are insulating layers; the lower half of the probe is provided with a three-component geophone, An inclinometer is installed at the lower part of the three-component geophone, the friction cylinder is located below the inclinometer, a pore water pressure sensor is installed in the middle of the friction cylinder, a probe is connected to the bottom of the friction cylinder, and the pore pressure filter ring is located at the friction The connection between the barrel and the probe.

The cone angle of the probe is 60°, the cross-sectional area of the cone bottom is 10cm ² , and the surface area of the friction cylinder is 150cm ² .

The pore pressure filter ring has a thickness of 5 mm and is located at the cone shoulder. The effective area ratio of the probe is 0.8.

The resistivity static penetration probe of the utility model has a resistivity testing part mainly composed of two copper ring electrodes and an internal circuit system. The copper electrodes are separated by insulating plastic to form an O-ring sealing system. Through its internal circuit system and two electrodes synchronously, continuously measure the voltage change between the two internal electrodes, and calculate the resistivity of the soil around the electrodes.

Beneficial effects: Because the in-situ resistivity of the soil measured by the resistivity static penetration probe is one of the basic parameters of the soil, it is closely related to the structure, void ratio, water content and composition of the soil, and its change can effectively reflect the basic parameters of the soil. Changes in characteristic parameters. Therefore, the foundation treatment effect can be evaluated by comparing the resistivity before and after foundation reinforcement. This technology has the characteristics of continuity, reliability and repeatability.

Assuming that the soil property parameter a and the cementation coefficient m remain unchanged before and after foundation treatment, the porosity ratio n′/n before and after foundation treatment is defined according to the Archie model (in the formula, ′ represents the value after foundation treatment):

n′/n=((ρ′/ρ)·(ρ _w /ρ _w ′)) ^-1/m

In the formula, n' is the porosity of soil after foundation treatment; n is the porosity of soil before foundation treatment.

Used in the field test of resistivity static penetrating sounding, the groundwater resistivity test and the assumed m value can be used to evaluate the porosity ratio of the soil before and after foundation treatment. For example, after foundation treatment, the porosity of sandy soil decreases, and the foundation becomes denser. In the area where the disturbance is greatly affected during the probe penetration process, the size and distribution of the volumetric strain change with the density and stress level, and the actual measurement proves that both of them have been improved after the foundation treatment. The change in resistivity before and after reinforcement of another vibration-displaced site has been confirmed.

Description of drawings

Fig. 1 is the measurement schematic diagram of the utility model;

Among them are: insulating plastic 1, ring electrode 2, three-component geophone 3, inclinometer 4, friction cylinder 5, pore water pressure sensor 6, probe 7, pore pressure filter ring 8.

Detailed ways

The outer circumference of the upper half of the resistivity static penetration probe of the utility model is covered with two ring electrodes 2, and the two sides of the ring electrodes 2 are insulating layers 1; a three-component geophone 3 is provided at the lower half of the probe, An inclinometer 4 is arranged at the bottom of the three-component geophone 3, and a friction cylinder 5 is located below the inclinometer 4. A pore water pressure sensor 6 is arranged in the middle of the friction cylinder 5, and a probe is connected below the friction cylinder 5. 7. The pore pressure filter ring 8 is located at the connection between the friction cylinder 5 and the probe 7 . The cone angle of the probe 7 is 60°, and the cross-sectional area of the cone bottom is 10cm ² .

The probe integrates the functions of conventional static penetration testing (measurable end resistance, friction resistance, inclination and pore pressure) and soil resistivity testing functions. The resistivity of soil is the basic parameter to characterize the conductivity of soil, and it is one of the inherent physical parameters of soil, which depends on the porosity, pore shape, pore fluid resistivity, saturation, solid particle composition, shape, orientation, bonding state, etc. The change law of soil resistivity and its related indexes reflects the change law of physical and mechanical property indexes of soil. Therefore, static CPT technology based on resistivity can be used to evaluate the effect of foundation treatment. The core part of the resistivity static penetration probe equipment is the resistivity sensor, and the probe adopts a four-electrode arrangement to eliminate possible errors caused by gas generation and electroplating. The probe has a special electric servo system, which uses automatic correction technology to ensure the test accuracy in the range of 0-10000ms/s. The probe specifications conform to international standards: the cone angle is 60°, the cross-sectional area of the cone bottom is 10cm ² , and the area of the side wall friction cylinder is 150cm ² .

Three-component geophone 3: model m317259, natural frequency 100HZ/60HZ, sensitivity 104mV/kine, impedance 215Ω.

Gyro inclinometer 4: Vertex angle measurement range: 0°～15°; Accuracy: ±0.1°; Vertex angle resolution: 0.01°;

As shown in Figure 1 is the schematic diagram of the measurement. Due to the complexity of the electric field in the soil around the probe rod and the difficulty in controlling the boundary conditions, the soil electrical characteristics measured by the probe are very complicated. The theoretical equation of the penetrating test is obtained through Ohm's law. The soil resistivity is obtained by measuring the voltage drop ΔV between the two electrodes under constant current and calculating the resistance R of the soil according to Ohm's law. The vertical resistivity ρ of the sample can be expressed as:

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; RS</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;\; VS</span>}}{\mathrm{<span\; class="notranslate">\; IL</span>}}$

In the formula, S is the electrode area (m ² ), L is the electrode spacing (m), and I is the current intensity (A).

Due to the complexity of the boundary conditions, the electrical characteristics of the soil obtained by the probe are very complicated. The theoretical equation of the penetrating test is obtained by Ohm's law:

ρ=π ² ΔV/(CI)

In the formula, C=1/(d+r _M )-1/(d+rr _M )-1/(d+r _N )+1/(d+rr _N ), ρ is the resistivity of soil, and ΔV is The voltage difference, I is the current.

Claims (3)

1. A resistivity static penetration probe is characterized in that two ring electrodes (2) are wrapped in the periphery of the upper half of the probe, and the upper and lower sides of the ring electrode (2) are insulating layers (1); A three-component geophone (3) is provided at the lower part of the probe, an inclinometer (4) is provided at the lower part of the three-component geophone (3), and the friction cylinder (5) is located below the inclinometer (4) , a pore water pressure sensor (6) is provided in the middle of the friction cylinder (5), a probe (7) is connected below the friction cylinder (5), and a pore pressure filter ring (8) is located between the friction cylinder (5) and the probe ( 7) The connection. 2. The resistivity static penetration probe according to claim 1, characterized in that the cone angle of the probe (7) is 60°, the cross-sectional area of the cone bottom is 10cm ² , and the surface area of the friction cylinder is 150cm ² . 3. The resistivity static penetration probe according to claim 1, characterized in that the pore pressure filter ring (8) has a thickness of 5mm, is located at the cone shoulder position, and has an effective area ratio of the probe of 0.8.

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