RU2446251C1 - Method and device to test soils with static and dynamic load - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to test soils with static and dynamic load consists in the fact that soil testing is done in steps or continuously with the specified speed of screw stamp movement from the specified load stage with account of deformation due to bend of hollow rod segments. At the same time the device for realisation of the specified method comprises a screw stamp, a hollow pump rod made of segments, a loading accessory, measurement accessories, made in the form of a linear displacement sensor, and a loading mechanism. Besides, inside each segment of the hollow rod there is a sensor unit, comprising an inclination sensor with digital output and a transceiver. Sensor units are connected into a single sensor network and send information along radio frequency to each other and to a remote computer.

EFFECT: higher accuracy of measurements of screw stamp subsidence, expansion of functional capabilities and higher efficiency of soil testing in field conditions.

11 cl, 5 dwg

Description

Technical field

The invention relates to engineering surveys in construction and can be used to determine the deformation and strength characteristics of soils in the field.

Technical field

An analogue of this proposed invention is an installation for testing soil under static load (copyright certificate for the invention SU 367363 A1, application 1633584 dated 03/09/1971, IPC G01N 3/42, published 01/23/1973, bull. No. 8), including a load hydraulic system with measuring devices , a hollow anchor pile and a loading rod with a screw die, characterized in that in order to increase the accuracy of measurements when testing the soil, the loading rod is mounted in the cavity of the anchor pile with the possibility of movement along its axis.

A disadvantage of the known solution is that when creating a static load, the load rod bends inside the hollow anchor pile, which leads to an error in the measurement of the draft of the stamp.

The next analogue of the proposed technical solution is INSTALLATION FOR TESTING THE SOIL (copyright certificate for the invention SU 379875 A1, application 1639084 of 03/28/1971, IPC G01N 33/24, G01B 19/16, B30B 15/02, published on 04/20/1973, bull. No. 20), comprising a hydraulic loading system and a stamp interacting with the rod of the device for registering the draft of the stamp, characterized in that in order to reproduce the amount of draft of the stamp, the device for recording the draft of the stamp is made in the form of a displacement sensor mounted on the reference device, This is done with a pulse generator connected to a pulse counter and reversible stepping mechanisms, one of which is connected to the sensor contact, pivotally connected to the rod, and the other to the recording device.

A disadvantage of the known solution is that when creating a static load, the load rod bends, which leads to an error in the measurement of the draft of the stamp.

The closest analogue (prototype) of the claimed invention in terms of the method according to the technical essence and the total number of essential features is the method of testing soils with a screw stamp, implemented in the DEVICE FOR TESTING SOIL (copyright certificate for invention SU 1381245 A1, application 4076346 dated 06.06.1986, IPC E02D 1/00, published 03/15/1988, bull. No. 10), including a blade stamp, a hollow rod with a blade anchor, a load device in the form of a power hydraulic cylinder, a measuring device in the form of linear displacement sensors nye, and the loading mechanism, characterized in that in order to expand the range of the studied soils and increase the reliability of measurements, the blade anchor is installed with the possibility of free movement along the rod, the blade stamp is hollow, and the power hydraulic cylinder is placed in the cavity of the blade stamp and is in contact with the end face of the blade anchor, while linear displacement sensors are placed inside the cavity between the blade stamp and the rod.

The method consists in immersing hollow pipe columns equipped with a screw blade-stamp and a screw anchor at the lower end with the possibility of their limited axial movement both relative to each other and relatively pipe columns, and after immersion of the stamp to the depth of soil testing, the upper end of the pipe string is rigidly attached to the anchor device and soil tests are carried out by applying loads of specified steps to the stamp loading with measuring the draft of the stamp at each stage at predetermined time intervals until the conditional stabilization of the draft, and upon completion of one stage of loading go to the next stage of loading, and the loading device in the form of a power hydraulic cylinder is placed in the cavity of the pipe string in contact with the stamp and simultaneously with anchor, and the amount of draft of the stamp is determined by the difference between the movements of the stamp relative to the anchor and the anchor relative to the pipe string using linear displacement sensors, connect GOVERNMENTAL, as the load device, the feedback channel with the surface.

The disadvantage of the prototype is the low accuracy of measuring the draft of the stamp at a significant depth of testing due to the neglect of the longitudinal bending of the rod, which is inevitable with a significant depth of testing and significant load. Another disadvantage is the use of wired communication channels for transmitting signals from displacement sensors to the surface of the soil, which complicates and reduces the test performance, since it is necessary to pass the cable through a set of rods before starting the tests. In addition, this device is applicable only to determine the deformation characteristics of soils and is not applicable to determine the strength characteristics of soils, which limits its capabilities.

The essence of the technical solution

An object of the invention is to increase the accuracy of measurements of the precipitation of a screw stamp, as well as expanding the functionality and increasing the productivity of soil testing in the field.

The technical problem posed in part of the method is solved by the fact that according to the invention, the hollow rod is made up of separate segments, inside each sensor unit is introduced, including a tilt sensor with a digital output and a transceiver connected wirelessly to a computer located on the ground surface, the load device is made in the form two servos, one of which is fixed on the console of the drilling rig, and the second is located inside the shank of the screw stamp and is fixed on one side on the flange, and on the second the side has a detachable connection for connecting the probe or sampler, the probe is equipped with a friction force sensor, drag sensor, pore pressure sensor and connected to a sensor node having a three-coordinate accelerometer with digital output and a transceiver connected wirelessly to other sensor nodes inside the hollow rod, and through them to a remote computer on the soil surface, and soil testing is carried out in steps or continuously with a given speed of vertical movement, measuring sediment die of a predetermined pressure level or pressure at a predetermined rate of vertical movement of the screw die, wherein the die design value determined by precipitation with the bending of the hollow rod, using the following expression:

s = s _stamp -s _boom ,

where s is the estimated value of the draft stamp; s _stamp - the measured value of the precipitation of the stamp sensor linear displacements from the soil surface; s of the _rod - the error of measuring the draft of the stamp due to the longitudinal bending of the hollow rod, which is determined using the following procedure.

Figure 4 shows the drill rod of their three segments of hollow rods (K = 3). The first segment of the hollow rod is on top. Tilt sensors are designated as S ₁ , ..., S _k . The length of one segment of the hollow rod is L. The vertical axis is denoted by V. The horizontal planes are denoted by H ₁ , ... H _k . The inclination angles (Fig. 4) are measured with respect to the V axis in the planes VON (angle α) and VOE (angle β).

To calculate the vertical displacement (ΔLH) of each segment of the hollow rod when they deviate from the vertical axis relative to the horizontal plane (H), the following initial data are necessary (Figs. 4, 5):

- α ₁ , ..., α _k is the measured angle of inclination of the segment of the hollow rod in the plane VON;

- β ₁ , ..., β _k is the measured angle of inclination of the hollow rod segment in the VOE plane;

- L is the length of one segment of the hollow rod;

- k is the number of segments of the hollow rod.

L _vi - the projection length of the i-th segment of the hollow rod on the vertical axis V is calculated by the formula:

L _vi = Lcosα _i cosβ _i .

The vertical movement of each segment of the hollow rod when they deviate from the vertical is calculated by the formula:

ΔLH _i = L _i -L _vi .

The vertical movement of the entire hollow rod due to bending is calculated as the sum of the vertical movements of individual segments of the hollow rods according to the formula:

The next distinctive feature of the invention is the introduction of two interchangeable elements in the form of a probe and a thin-walled cylindrical sampler into the design of a screw stamp. This allows, at one point of the soil massif at any depth, to simultaneously conduct not only tests with a screw stamp, but also tests with a probe or select a soil monolith. Currently, for this purpose, a separate screw die and a static sensing device are used, which have their own loading and measuring systems, which is more time-consuming and significantly more expensive, since various technologies are used.

Tests with a screw stamp and a probe at one point in the soil array allow both strength (probe) and deformation (screw stamp) soil characteristics to be determined, which extends the functionality of the known invention and reduces the cost of testing.

Another advantage of the invention is that the device also allows you to select monoliths of soil. The selection of the soil monolith at the test point with a screw stamp allows laboratory tests, for example, tests under triaxial compression (GOST 12248-96). As a result, two values of the deformation modulus can be obtained from field and laboratory tests, which allows one to find correlation between different experimental values of the deformation modulus and more accurately assign the calculated value of the deformation modulus used in the design of foundations and foundations of buildings and structures.

The presence of a wireless system for transmitting data from sensors to a computer, as well as the use of wireless communications to control the process of power loading improves the technical characteristics of the known invention. There is no need to perform the operation of passing the cable through a set of hollow rods and then to the measuring system. This not only improves working conditions, but also reduces the time it takes to prepare the tests, which together increases the productivity of field soil tests.

The introduction of the accelerometer in the design of the screw die also extends the functionality of the invention. The proposed method allows to determine not only the deformation modulus used in the design of the foundations of buildings and structures, but also the elastic deformation modulus used in the design of structures taking into account seismic or dynamic effects.

List of figures, drawings and other materials

Figure 1 shows a drilling rig with a set of equipment for implementing the proposed method and device, General view.

Figure 2 shows the design of the lower part of the screw die with a probe.

Figure 3 shows the design of the lower part of the screw stamp with a sampler.

Figure 4 shows the design scheme for determining the precipitation of the screw stamp due to the longitudinal bending of the hollow rod.

Figure 5 shows a diagram of the vertical displacement of the i-th segment of the hollow rod relative to the horizontal plane.

An example of the implementation of a technical solution

Figure 1 shows the drilling rig 1, set on the triggers 2 and secured by screw anchors 3, equipped with a rotary mast 4 with a rotator 5 movable along the mast using the hydraulic cylinders of the machine with the output shaft 6, which abuts against the console 7, which is pushed into the socket 8, fixed on the chassis of the drilling rig. A servo drive 9 is vertically fixed to the bottom of the console and connected wirelessly via a data acquisition unit 20 via an interface 21 to a remote computer 22. A screw stamp 10 with a shank 11 is attached to the lower segment of the hollow rod 12. Inside each segment of the hollow rod, sensor assemblies are installed, including two-coordinate tilt sensors 13, which wirelessly transmit signals from the sensors in digital form to a transceiver 14 located inside the upper segment of the hollow rod and connected wirelessly and at a frequency of 2.5 GHz to the data acquisition unit 20. A support head 15 is mounted on the upper segment of the hollow rod, on which four consoles are fixed 16. The reference system consists of four racks 17 with movable brackets, on which digital linear displacement sensors 18 are fixed by holders A digital force sensor 19 is installed on the head 15. The force sensor 19 and four linear displacement sensors 18 are connected wirelessly to the data acquisition unit 20, which is connected to the computer 22 through the interface 21. For centering the hollow rod, tal apron 23, installed at the wellhead.

Figure 2 additionally shows a cross section of a screw stamp with a shank, a cylindrical probe is placed inside the shank, including a sensor 25 for measuring friction, a drag sensor 26 in the form of a cone at an apex of 60 °, a pore pressure sensor 27. The probe is connected to the actuator rod 24 28, and the servo drive itself is mounted on the flange 29. The output of the friction force sensor 25, the drag sensor 26, the pore pressure sensor 27, the stepper motor control channel are connected to the data acquisition and control unit 30, including three-axis accelerometer 31, a signal amplifier, an analog-to-digital and digital-to-analog converters, radio transmitter and receiver to the antenna 32. In the lower conical part of the screw die 10 has a conical flange 35 with packing gland 33, the gland inner diameter corresponds to the outer diameter of the probe.

The power source for the control unit and the stepper motor is lithium batteries 34.

Figure 3 additionally shows a cross section of a screw stamp with a shank, in the lower part of the screw stamp there is a thin-walled sampler 36 attached by a rod 24 to the servo drive 28.

The axial load on the screw stamp is created using the servo 9. The axial load on the probe or sampler is created using the second servo 28.

In figure 4 are indicated:

H1, H2, H3 - horizontal planes; L is the length of one segment of the hollow rod; S ₁ , S ₂ , S ₃ - tilt sensors.

Figure 5 marked:

S is the initial position of the tilt sensor; S '- the position of the tilt sensor after the offset; α is the measured angle of inclination of the segment of the hollow rod in the VON plane; β is the measured angle of inclination of the hollow rod segment in the VOE plane; L is the length of the segment of the hollow rod; L _v - the projection of the segment of the hollow rod on the V axis; R is the distance from the tilt sensor S 'to the V axis; R _VOE is the projection of the vector R onto the VOE plane; R _VON is the projection of the vector R onto the VON plane.

On the device shown in Fig.1-3, which implements the proposed method, work on the preparation and testing of soils, as follows.

1. Install the drilling rig 1 at a given test point using an inclinometer connected to a computer, and the triggers raise and level the rig position horizontally. At loads greater than the weight of the drilling rig in the direction of the triggers, screw anchors 3 are screwed vertically or obliquely into the ground.

2. Using the drilling machine 1 pass the well to a predetermined depth, depending on the type of soil with or without casing. The inner diameter of the casing or well is taken equal to the diameter of the screw die.

3. To the hollow rod 12 attach the shank 11 of the screw stamp 10 and, using the winch of the drilling rig, lower them into the drilled well until the bottom of the well.

4. At the wellhead, an apron 23 is installed and, using the readings of inclinometers, using a computer, the axis of the hollow rod is installed strictly vertically.

5. Using the mechanism of the drilling rig, lower the shaft 6, connect it to the hollow rod 12, turn on the actuator 5 and screw the screw stamp into the ground to a depth of 30-40 cm below the bottom of the well.

6. Release the shaft 6 from the hollow rod 12 and raise the shaft to its initial position. Then, the console 7 is inserted into the socket 8 and the shaft 6 is lowered into the console until it stops.

7. At the top of the hollow rod, a support head 15 with consoles 16 and a force sensor 19 are installed, which is connected wirelessly to the data acquisition unit 20.

8. To the bottom of the console fix the servo 9, which is connected wirelessly to the data acquisition unit 20.

9. Tests to determine soil strength parameters.

9.1. At the command of the computer, the servo drive 28 is turned on and the probe is pressed into the ground at a given speed (mm / min), while the readings are taken from the sensors of friction, drag and pore pressure. The readings of the sensors using the data acquisition and control unit 30 are transmitted over the licensed frequency 2.5 GHz to the transceiver 14, then to the data acquisition unit 20 and through the interface 21 are recorded in the computer's memory 22. The probe indentation speed and the magnitude of its movement are controlled by the number of pulses supplied on a stepper servo motor. After the probe is completely extended from the screw die, the servo drive is disconnected at the command of the computer.

9.2. Using the values of the friction forces, drag, and pore pressure, the soil strength parameters are determined by the internal friction angle φ and the specific adhesion force c, and using the corresponding nomograms, the type of soil is determined.

10. Tests to determine the deformation characteristics of soils.

10.1. At the command of the computer, the servo drive 9 is turned on and the axial load on the screw stamp is applied in 10 steps with exposure at each step until the draft is conditionally stabilized or continuously with a predetermined draft speed (mm / min). The values of the draft of the screw stamp s of the _stamp , measured using four linear displacement sensors on the soil surface, and the applied pressure p under the screw stamp are recorded in the database. At the same time, in the process of loading a screw stamp, the readings of inclinometers installed inside the segments of the hollow rod are recorded and, using the following procedure, the error of measuring the draft of the stamp due to the longitudinal bending of the hollow rods is determined.

Figure 4, 5 shows a hollow rod, consisting for example of three segments of hollow rods (K = 3). The first segment of the hollow rod is on top. Tilt sensors are designated as S ₁ , ..., S _k . The length of one segment of the hollow rod is L. The vertical axis is denoted by V. The horizontal planes are denoted by H ₁ , ... H _k . The inclination angles (Fig. 4) are measured with respect to the V axis in the planes VON (angle α) and VOE (angle β).

To calculate the vertical displacement (ΔLH) of each segment of the hollow rod when they deviate from the vertical axis relative to the horizontal plane (H), the following initial data are required (Fig. 5):

- α ₁ , ..., α _k is the measured angle of inclination of the segment of the hollow rod in the plane VON;

- β ₁ , ..., β _k is the measured angle of inclination of the hollow rod segment in the VOE plane;

- L is the length of one segment of the hollow rod;

- k is the number of segments of the hollow rod.

L _vi - the projection length of the i-th segment of the hollow rod on the vertical axis V is calculated by the formula:

L _vi = Lcosα _i cosβ _i .

The vertical movement of each segment of the hollow rod when they deviate from the vertical is calculated by the formula:

ΔLH _i = L _i -L _vi .

The vertical movement of the entire hollow rod due to bending is calculated as the sum of the vertical movements of individual segments of the hollow rods according to the formula:

.

.

10.2. The loading of a screw die is carried out to a load determined within the linear portion of the dependence of the draft of the screw die on pressure, the pressure being defined as the sum of the external load (s), the weight of the hollow rod and the screw die, divided by the area of the screw die.

10.3. Calculate the calculated value of the precipitation of the screw stamp, taking into account the bending of the hollow rod:

s = s _stamp -s _boom .

10.4. Using the calculated value of the draft s and the applied pressure p, according to the formula GOST 20276-99 "Methods for the field determination of deformability characteristics" find the stamped deformation module:

where E is the deformation modulus; v is the Poisson's ratio; k ₁ is a dimensionless coefficient; d is the diameter of the stamp; k ₂ is a dimensionless coefficient; Δp is the pressure increment; Δs is the calculated value of the increment of the upsetting stamp corresponding to the increment of pressure Δp and determined taking into account the bend of the drill rod.

11. Tests to determine the dynamic characteristics of soils.

11.1. A steel plate is inserted under one of the triggers.

11.2. Using a hammer with a mass of 5-8 kg with a force sensor, they strike a steel plate. The synchronization of the impact time and the start of recording soil vibrations by the accelerometer 31 is performed by transmitting the signal from the force sensor wirelessly through the sensor nodes to the data acquisition and control unit 30 and starts recording data from the accelerometer to the internal memory of the block.

11.3. The resulting elastic vibrations of the soil are recorded by the accelerometer 31, the accelerogram of the vibrations is recorded in the internal memory of the data acquisition and control unit 30 and transmitted sequentially through the sensor nodes to the memory of the computer located on the soil surface via a computer command via wireless communication.

11.4. Using the accelerogram, the shear wave velocity V _{s is found} .

11.5. Using the well-known expression, the shear wave velocity V _s and the elastic shear modulus G are determined:

,

,

where ρ is the density of the soil.

12. Sampling of soil for laboratory tests during testing with a screw stamp.

12.1. The probe is replaced by a thin-walled cylindrical sampler 36 (Fig. 3), which, after screwing a screw stamp into the soil, is immersed in the soil under the stamp using a servo drive 28, which leads to the selection of the soil monolith in the internal cavity of the sampler.

12.2. Tests are carried out with a screw stamp in paragraphs 10-11.

12.3. After testing with a screw stamp, the servo drive is turned on and the sampler is inserted inside the screw stamp, after which the screw stamp rises to the ground surface.

12.4. The servo is turned on and the sampler is pulled out of the screw die, then unscrewed and replaced with a new one or with a probe, depending on the purpose of the test.

Industrial applicability

This invention is industrially feasible, has new, broader functionality and high productivity testing of soil in the field, increased measurement accuracy.

Claims (11)

1. A method of testing soils with static and dynamic loads, using a screw stamp, a hollow rod, a load device in the form of a power hydraulic cylinder, measuring devices in the form of a linear displacement sensor and a loading mechanism, characterized in that the soil test is carried out in steps or continuously with a given screw speed stamp, measuring the draft of the stamp from a given load stage, taking into account deformation due to the bending of the segments of the hollow rod, while the calculated value of the draft of the stamp is determined derived from the expression:
s = s _stamp -s _boom ,
where s is the estimated value of the draft stamp; s _stamp - the measured value of the precipitation of the stamp sensor linear displacements from the soil surface; s of the _rod - the error of measuring the draft of the stamp due to the longitudinal bending of the hollow rod, which is determined by the measured values of the angles of rotation of the segments of the hollow rod by tilt sensors and the design scheme using the expression:

where ΔLH _i is the vertical movement of each segment of the hollow rod when they deviate from the vertical due to the bending of the hollow rod, the test to determine the dynamic characteristics of the soil is carried out using a steel plate and a hammer with a force sensor that perform a strike on a steel plate, synchronizing the impact time and start recording soil vibrations with an accelerometer by transmitting a signal from a force sensor wirelessly through sensor nodes to a data acquisition and control unit, start recording data from an accessory In the internal memory of the unit, the resulting elastic vibrations of the soil are recorded by the accelerometer, the accelerogram of the vibrations is recorded in the internal memory of the data acquisition and control unit and transmitted by wireless computer command through the sensor nodes to the memory of the computer located on the soil surface using the accelerogram to find the transverse speed waves V _s and elastic shear modulus G:

where ρ is the density of the soil. 2. The method according to claim 1, characterized in that at the same time at the same test depth, the strength and deformation characteristics of the soils are determined. 3. The method according to claim 1, characterized in that at the same time as soil testing with a screw stamp, monoliths of soil are selected, parallel tests of soil samples are carried out in triaxial compression devices, and the values of the calculated deformation modulus are taken from a comparative analysis of the results of testing with a screw stamp and under triaxial conditions compression. 4. The method according to claim 1, characterized in that during the testing of the soil with a screw stamp, the dynamic characteristics of the soils are additionally determined. 5. The method according to claim 1, characterized in that the loading of the screw stamp is performed in steps, as well as continuously with the control of the settling speed of the screw stamp and probe. 6. A device for testing soils with static and dynamic loads for implementing the method according to claims 1-5, including a screw die, a hollow rod, a loading device in the form of a power hydraulic cylinder, measuring devices in the form of a linear displacement sensor, and a loading mechanism, characterized in that the load device is made in the form of a hollow rod assembled from separate segments, a sensor unit is introduced inside each segment, including a tilt sensor with a digital output and a transceiver, while evil connected into a single wireless sensor network and transmitting information on the radio frequency to each other and to a remote computer located on the ground surface. 7. The device according to claim 6, characterized in that the loading device has two servos, one of which is located on the surface of the soil, and the second inside the screw die, while the operation of the servos is automatically controlled by the program using a remote computer using sensor nodes and wireless connection. 8. The device according to claim 6, characterized in that a probe is inserted inside the screw die, including a friction force sensor, a drag sensor, a pore pressure sensor, while the probe is connected by a detachable connection to the servo drive, and the sensors are connected to the sensor assembly. 9. The device according to claim 6, characterized in that in the shank of the screw stamp there is a data acquisition and control unit including a three-axis accelerometer, a signal amplifier, analog-to-digital and digital-to-analog converters and internal memory. 10. The device according to claim 6, characterized in that it further comprises a hammer that has a force sensor, and the synchronization of the impact time and the start of recording soil vibrations by the accelerometer is performed by transmitting a signal from the force sensor wirelessly through the sensor nodes to the data acquisition unit and management. 11. The device according to claim 7, characterized in that a thin-walled cylindrical sampler is connected to the servo drive inside the screw stamp through a detachable connection.

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