RU2743547C1 - Method for monitoring the condition of permafrost soils serving as base for buildings and structures, and device for implementing it - Google Patents

Abstract

FIELD: geotechnical monitoring.

SUBSTANCE: invention relates to geotechnical monitoring of permafrost soils and is intended for predicting the critical settlement of foundations of buildings and structures on permafrost soils. Method for monitoring the conditions permafrost soils serving as the basis for the foundations of buildings and structures includes excitation of vibrations, determination of the speed and arrival time of a longitudinal wave passing through the soil mass. At the stage of geotechnical surveys, the static modulus of deformation of permafrost soils is determined, taking into account the load out of the future structure; after the installation of the pile foundation at the pile, observation wells are drilled diametrically; the depth and distance between them are determined according to the results of computer modeling of the soil foundation stress-strain state. To prevent the collapse of the borehole walls, concrete lining is installed in them, and concrete anchor slabs are installed on the surface. Then, low-frequency emitting and receiving ultrasonic transducers with dry point contact are placed in the wells; each transducer has its own serial number, which corresponds to the pile number. Then the ground is sequentially scanned and the time of the longitudinal wave propagation is determined at each position of the emitting and receiving transducers. The obtained data are transmitted to the PC and the velocity of propagation of the longitudinal ultrasonic wave and the dynamic deformation modulus of permafrost soils are calculated, after which the correlation dependence between the dynamic deformation modulus and the static deformation modulus of soils is determined. At the stage of the structure operation periodic measurements of the longitudinal ultrasonic wave propagation time are performed, the dynamic modulus of soil deformation is calculated, after which the static modulus of deformation is recalculated using the previously obtained correlation dependence, the estimated settlement of the structure foundation is performed, and a conclusion is drawn about the state of the permafrost mass.

EFFECT: technical result consists in providing the possibility of continuous monitoring of the permafrost soils deformation properties.

3 cl, 1 tbl, 5 dwg

Description

The invention relates to geotechnical monitoring of permafrost and is intended to predict the critical settlement of foundations of buildings and structures on permafrost.

There is a known method for monitoring the position of pipelines for aboveground laying in permafrost conditions (patent RU No. 2582428, publ. 04/27/2016), which includes the following steps: installation on piles of pipe supports of deformation marks, installation of soil depth benchmarks, installation along the pipeline of reference stations, then determine their coordinates in the state network and translate them into local coordinates, after which a zero cycle of measurements of the coordinates of deformation marks relative to soil depth benchmarks is carried out in the local coordinate system, the zero horizontal-height position of the pipeline is determined and, based on the results of all measurements, a design digital model is built pipeline, then, during the operation of the pipeline, using mobile GPS / GLONASS receivers, control measurements of the coordinates of deformation marks characterizing the current planned-high-altitude position of the pipeline are carried out, the measurement data is transmitted to the server and the current digital model of the pipelines is built rovoda.

The disadvantage of this method is that the system records the changes in the position (precipitation) of the pipeline that have already occurred and does not allow predicting further changes in the position of the pipeline due to changes in soil properties.

There is a known method for monitoring soil parameters (patent RU No. 2613907, publ. 03/21/2017), which includes the following steps: drilling wells, placing soil temperature sensors in wells at different depths, backfilling of wells, registered information about measured temperature is transmitted from sensors to a database on remote servers.

The disadvantage of this method is that when assessing the state of the array of permafrost soils, only the soil temperature is an informative parameter. Despite the fact that the physical and mechanical properties of permafrost soils directly depend on temperature, it is impossible to predict the loss of bearing capacity based only on temperature indicators. This is due to the fact that the transition of soils from a solid-frozen state to a plastic-frozen state is possible with the slightest change in temperature by 0.1 ° C.

There is a known method for monitoring temperature anomalies in permafrost soil of the line of a linear object (patent RU No. 2669602, publ. 12.10.2018), which consists in the following: according to signals from temperature sensors, a layer with a thawing boundary is determined, then weight coefficients are determined for the upper layers of permafrost soil and find a layer-weighted temperature model, then determine the weight coefficients for the thermometric wells of the site and find the weighted temperature model of the site, then find the temperature deviations and, in accordance with the a priori data, find out the maximum permissible deviation of the site temperature and compare it with the obtained deviations.

The disadvantage of this method is that the thawing temperature of the same type of soil can differ significantly and depends on the chemical, mineral composition of groundwater and many other factors, therefore, detecting a site where the temperature is elevated does not mean that at the moment the base may lose its bearing ability on this site.

A known method for predicting the onset of destruction of the foundations of buildings and structures and a device for its implementation (patent RU No. 2100806, publ. 27.12.1997), which includes measuring the parameters of acoustic emission at the temperature of the transition of soil from a solid-frozen state to a plastic-frozen state, the moment of destruction of bases is determined by a sharp decrease in the amplitude-frequency parameters of acoustic emission.

The disadvantage of this method is that the use of a passive acoustic control method allows you to give only a short-term forecast.

There is a known method for measuring the settlement of foundations and a device for its implementation "(patent RU No. 2413055, publ. 02/27/2011), which consists in periodically measuring the position of the mark located on the foundation relative to the practically stationary benchmark, the position of the mark in height is measured by a linear sensor displacement with a converter of displacement values into an electrical signal.

The disadvantage of this method is that the method does not allow to determine the changes in the deformation properties of the frozen base, which entailed settlement of the structure and to predict the critical settlement of the base.

There is a known method for controlling the thickness of the ice wall during the construction of mine shafts (patent RU No. 2706910, publ. 11/21/2019), taken as a prototype of the method, which consists in registering reflected seismoacoustic signals with a piezoelectric seismic receiver. A system consisting of an electric spark source of seismic vibrations and a garland of piezoelectric geophones is installed in the control wells. The installed system is displaced along the wellbore and seismoacoustic signals are recorded. Next, the arrival times and propagation velocity of longitudinal waves are determined, on the basis of which the thickness of the ice-rock mass is judged.

This method is not considered as a method for continuous monitoring of subsoil. The disadvantage of this method is that the measurements do not determine the deformation properties of soils and their change.

A device for geotechnical diagnostics and monitoring of main pipelines in the permafrost zone is known (patent RU No. 139945, publ. 04/27/2014), which includes a soil temperature sensor, a pipeline temperature sensor, a pipeline deformation sensor, and a data collection unit. The data collection unit contains a control unit and a data processing unit. The pipeline strain gauge consists of three fiber-optic sensor cables attached along the entire monitored object under a heat-insulating layer. The pipeline temperature sensor consists of a fiber optic sensor cable, which is also located along the entire length of the monitored section. The ground temperature sensor is a fiber optic sensor cable located in the ground, away from the thermal insulation of the pipeline. All sensors are connected to the data acquisition input.

The disadvantage of the device is that the deformation sensor is installed directly on the pipeline and records the deformations of the pipeline that have already occurred as a result of thawing of permafrost soils, that is, this device does not allow predicting the deformations of the pipeline and soil foundations.

There is a known device for automated geotechnical monitoring for underground pipelines (patent RU No. 2672243, publ. 12.11.2018), which is fixed on the pipeline with the help of flexible fixation elements of a curved base, on which a supporting post is installed, two additional posts are fixed on the side of the post ... A temperature sensor is installed inside the first additional rack, which is connected to a logger installed in the second additional rack. Two thermal converters are installed inside the carrier. A reflector, deformation mark, junction and switch boxes are installed on the support.

The disadvantage of the device is that the established deformation mark, for measuring the horizontal-height position, is an indicator of changes that have already occurred and does not allow predicting them, in order to prevent, and the installed temperature sensors do not allow to reliably assess the change in the thermophysical and deformation properties of the soil, since thawing permafrost is a complex and multifactorial process that depends not only on changes in soil temperature.

There is a known method for predicting the onset of destruction of the foundations of buildings and structures and a device for its implementation (patent RU No. 2100806, publ. 27.12.1997). The device consists of a ground temperature sensor, two signal preamplifiers, a waveguide with a piezoelectric sensor for acoustic emission, a bandpass filter with a built-in amplifier, an analog-digital processing unit, and a memory device.

The disadvantage of the device is that the use of acoustic emission sensors for predicting the onset of the destruction of foundations is complicated by the fact that acoustic emission pulses are difficult to separate from noise.

Known hardware complex of pulsed acoustic transmission and sounding APZ-1 (developed by OOO Geodiognostika, Russia, 2006 Geodiagnostics: [https://geodiagnostics.ru/APZ.htm]), taken as a prototype device, which consists of a pulse generator current, electric spark emitter, receiver of elastic waves, geophysical and radio frequency cable, voltage amplifier, personal computer with installed software.

The disadvantage of the device is the electro-hydraulic method of exciting elastic waves. The emitter and receiver are located in water-filled wells, which causes difficulties when working in a permafrost zone. Also, this hardware complex is not considered as an autonomous system for continuous monitoring of the state of permafrost foundations.

The technical result of the method is the ability to continuously monitor the deformation properties of permafrost soils.

The technical result is achieved by the fact that at the stage of engineering and geological surveys, the static modulus of deformation of permafrost soils is determined, taking into account the load from the future structure, after the installation of the pile foundation, at the pile, diametrically, observation wells are drilled, the depth and distance between them are determined by the results of computer modeling intensely - the deformable state of the subgrade, while, to prevent the collapse of the walls of the wells, a concrete lining is installed in them, and concrete anchor plates are installed on the surface, then low-frequency emitting and receiving ultrasonic transducers with dry point contact are placed in the wells, for each transducer its own ordinal number, which corresponds to the number of the pile, then sequentially carry out the sounding of the soil and determine the propagation time of the longitudinal wave at each position of the emitting and receiving transducers, the obtained data is transmitted to the PC and producing t calculation of the propagation velocity of a longitudinal ultrasonic wave and the dynamic modulus of deformation of permafrost soils, after which the correlation dependence between the dynamic modulus of deformation and the static modulus of soil deformation is determined, at the stage of operation of the structure, periodic measurements of the propagation time of a longitudinal ultrasonic wave are performed, the dynamic modulus of soil deformation is calculated, after which , according to the correlation dependence obtained earlier, the static modulus of deformation is recalculated, the calculation of the estimated settlement of the foundation of the structure is carried out and a conclusion is made about the state of the array of permafrost soils.

The technical result is the creation of a device for the use of low-frequency ultrasonic transducers with dry point contact, which allows you to solve the problem of ensuring the acoustic contact of the transducer with the borehole wall, to identify various changes in the array of permafrost soils.

The technical result is achieved by the fact that the device is additionally equipped with low-frequency receiving and transmitting ultrasonic transducers with dry point contact, which are connected through switches to a device for measuring the propagation time of a longitudinal ultrasonic wave, switches and a device for measuring the propagation time of a longitudinal ultrasonic wave are connected to a PC via a USB cable , low-frequency receiving and emitting ultrasonic transducers with dry point contact are installed in the wells using a device for suspending and providing contact of the transducer with the borehole wall, which includes a tension stud, a coupling, a connecting stud, a connecting tee and steel pipe, a clamping angle is rigidly attached to the lower end of the steel pipe, to which a low-frequency receiving or emitting ultrasonic transducer with a dry them with point contact.

A method for monitoring the state of permafrost soils serving as the basis for buildings and structures and a device for its implementation is illustrated by the following figures:

fig. 1 - general diagram of the monitoring system in section;

Fig. 2 is a general diagram of the monitoring system in plan;

Fig. 3 is a cross-sectional diagram of observation wells;

Fig. 4 is a diagram of suspension and contact of the transducer with the borehole wall;

Fig. 5 is a device for suspending and providing contact of the transducer with the borehole wall, where:

1 - PC with preinstalled software;

2 - a device for measuring the propagation time of a longitudinal ultrasonic wave;

3 - switch-demultiplexer;

4 - switch-multiplexer;

5 - emitting low-frequency ultrasonic transducer with dry point contact;

6 - receiving low-frequency ultrasonic transducer with dry point contact;

7 - signal amplifier;

8 - device for suspending and providing contact of the transducer with the borehole wall;

9 - geophysical cable with bayonet connector;

10 - pipe;

11 - connecting tee;

12 - clamping corner;

13 - clutch;

14 - connecting pin;

15 - tension pin;

16 - anchor;

17 - anchor plate;

18 - observation well;

19 - composite protective cap;

20 - pile foundation.

The method for monitoring permafrost soils is implemented as follows. At the stage of engineering and geological surveys, the static modulus of deformation of permafrost soils is determined. The static modulus of soil deformation is determined taking into account the load from the future structure. To determine the depth of observation wells 18 and the distance between them, computer modeling of the stress-strain state of permafrost soil, which serves as the basis for the pile foundation 20. After the installation of the pile foundation 20 (Fig. 3), two observation wells 18 are drilled at the pile, diametrically, to prevent the collapse of the walls of the wells, a concrete lining is installed in them. Next, anchor plates 17 are installed to attach the suspension device and ensure contact of the transducer with the borehole wall 8 (Fig. 4). In observation wells 18 (Fig. 3), an emitting low-frequency ultrasonic transducer with a dry point contact 5 (Fig. 3) and a receiving low-frequency ultrasonic transducer with a dry point contact 6 are installed, each transducer has its own serial number in the system corresponding to the pile number. After putting the facility into operation, from a PC with preinstalled software 1 (Fig. 2), an electrical signal is supplied to the emitting low-frequency ultrasonic transducers with dry point contact 5, and the time of propagation of a longitudinal ultrasonic wave between the corresponding wells is measured. Based on the measurement results, the velocity of propagation of the longitudinal ultrasonic wave is calculated and the dynamic modulus of deformation of permafrost soils is determined. Further, a correlation is established between the value of the static deformation modulus and the dynamic deformation modulus of permafrost soils. During the operation period of the structure, periodic measurements of the propagation time of a longitudinal ultrasonic wave are performed, the dynamic modulus of deformation of permafrost soils is calculated, the static modulus of soil deformation is calculated using a previously determined correlation dependence and possible settlements of the foundation of the structure are determined. All calculations are performed by software installed on PC 1.

The method is illustrated by the following examples. The physical basis for the application of the acoustic method to assess the deformation properties of permafrost soils during thawing is that the velocities of elastic waves, the dynamic modulus of deformation, as well as the static modulus of deformation characterize the soil's ability to deform. The method for monitoring the state of permafrost soils consists in the sensitivity of the velocity of propagation of a longitudinal ultrasonic wave to changes in the mass of permafrost soils. Monitoring consists in measuring the propagation time of a longitudinal ultrasonic wave in a mass of permafrost. Receiving and transmitting sensors are installed in wells drilled diametrically from the pile. The transducers installed in the wells are displaced along the wellbore, with a certain step. Measurements of the propagation time of the longitudinal ultrasonic wave are performed. After that, the speed of propagation of the longitudinal ultrasonic wave is calculated.

where l is the distance between the wells; T is the travel time of the elastic wave.

According to the obtained values of the propagation of the longitudinal ultrasonic wave velocity, the calculation of the dynamic modulus of elasticity of permafrost soils is performed:

;

;

– коэффициент Пуассона;

– плотность грунтов.Where

- Poisson's ratio;

- soil density.

Further, according to the obtained correlation dependence between the static deformation modulus and the dynamic deformation modulus, the static deformation modulus is calculated, after which the estimated foundation settlement is calculated by the layer-by-layer summation method. Based on the obtained values, a conclusion is made about the state of permafrost soils. Thus, the main parameter by which the changes in the deformation properties of permafrost soil are determined is the propagation speed of a longitudinal ultrasonic wave.

Using this method, it is possible to detect not only the temperature degradation of the permafrost massif, but also the appearance of leaching as a result of technogenic accidents. The sensitivity of the propagation velocity of a longitudinal ultrasonic wave to void defects has been repeatedly proven. This effect is widely used in practice.

The sensitivity of the velocity of propagation of a longitudinal ultrasonic wave to changes in temperature in the massif of permafrost has been proved experimentally. The results of the measurements of the velocity of the longitudinal ultrasonic wave during thawing of various samples are shown in Table 1.

Table 1 - results of measurements of the velocity of propagation of longitudinal ultrasonic waves in frozen soils, during their thawing.

Sand,
humidity 10% Sand,
humidity 20% t, ° C

, мкс

, μs

, m / s t, ° C

, μs

, m / s -15 52.84 1950 -15 44.86 2251 -ten 54.62 1885 -ten 47.34 2133 -five 70.64 1458 -five 63.78 1583 0 76.53 1345 0 66.37 1521 Loam,
humidity 20% Loam,
humidity 30% t, ° C

, μs

, m / s t, ° C

, μs

, m / s -15 47.56 2018 -15 49.78 2069 -ten 49.87 1928 -ten 52.76 1952 -five 62.57 1529 -five 60.57 1701 0 65.73 1460 0 65.78 1566

The data given in Table 1 were obtained in the course of experimental measurements of the propagation velocity of longitudinal ultrasonic waves in frozen soils, during their thawing. During the experiment, a temperature sensor was installed in the center of the frozen ground to control the temperature. The measurements were carried out when the soil reached certain temperatures. It should be noted that the thawing of the soil proceeded uniformly, in the direction from the edges to the center, and when the temperature reached -5 ° C in the center of the massif, a significant part of it had already thawed. The results of experimental studies should be divided into three stages. The first stage is the temperature range from -15 to -10 ° C, the second is from -10 to -5 ° C and the third is from -5 to 0 ° C.

At the first stage, over the entire temperature range, the soil massif was completely frozen. In this case, the value of the propagation velocity of the ultrasonic wave did not change significantly.

At the second stage, negative temperatures persisted only in the central part of the massif. The difference between the values of the velocity of propagation of an elastic wave, in the upper limit of the range and in the lower one, is significant.

In the third stage, the array was completely thawed. The states of the array, as in the first stage, became uniform. At the first stage the array was completely frozen, at the third stage it was thawed. The difference between the values of the propagation velocity of the longitudinal ultrasonic wave, as in the first stage, in the upper and lower limits of the range decreases to a minimum value.

It is also worth noting that the value of the propagation velocity of the longitudinal ultrasonic wave decreases throughout the experiment with increasing temperature.

A device for monitoring permafrost soils consists of a PC with preinstalled software 1 (Fig. 2), a device for measuring the propagation time of a longitudinal ultrasonic wave 2, a demultiplexer switch 3, a multiplexer switch 4, emitting low-frequency ultrasonic transducers with a dry point contact 5 , receiving low-frequency ultrasonic transducers with dry point contact 6, signal amplifiers 7 and a device for suspending and providing contact of the transducer with the borehole wall 8 (Fig. 4).

A PC with preinstalled software 1 (Fig. 2) is connected to a device for measuring the propagation time of longitudinal ultrasonic waves 2 (Fig. 2), a demultiplexer switch 3 and a multiplexer switch 4 (Fig. 2) using a USB cable ( not shown). The demultiplexer switch 3 and the multiplexer switch 4 are connected to a device for measuring the propagation time of a longitudinal ultrasonic wave 2 by means of geophysical cables with a bayonet connector (not shown). Emitting low-frequency ultrasonic transducers with dry point contact 5, connected to a demultiplexer switch 3, using a geophysical cable with a bayonet connector 9. Receiving low-frequency ultrasonic transducers with a dry point contact 6, connected to a signal amplifier 7 and a multiplexer switch 4, using a geophysical cables with bayonet connector 9. Emitting low-frequency ultrasonic transducers with dry point contact 5 (Fig. 3) and receiving low-frequency ultrasonic transducers with dry point contact 6, are installed in observation wells 18, using a device for suspending and providing contact of the transducer with the borehole wall 8 A device for suspending and providing contact of the transducer with the borehole wall 8 (Fig. 4), includes a pipe 10 (Fig. 5), made, for example, of steel, with threaded connections at both ends, the upper end of the pipe 10, using threaded connection, connected to the bottom to the end of the connecting tee 11, the lower end of the pipe 10, is welded to the clamping angle 12, the lateral end of the connecting tee 11, is connected to the coupling 13 using a connecting pin 14, the connecting pin 14 has a threaded connection at both ends, the coupling 13 through a threaded connection, connected to the tension pin 15, one end of the tension pin 15 (Fig. 4), made in the form of a ring and connected to the anchor 16, which is monolithic in the concrete slab-anchor 17. Emitting low-frequency ultrasonic transducer with dry point contact and receiving low-frequency ultrasonic transducer with dry point contact 6 (Fig. 5) are attached to the clamping angle 12 using clamps.

The device works as follows. A device is assembled on the surface for suspending and providing contact of the transducer with the borehole wall 8 (Fig. 4). A radiating low-frequency ultrasonic transducer with dry point contact 5 is attached to the clamping angle 12 (Fig. 5), a geophysical cable with a bayonet connector 9, previously passed through the pipe 10, is connected to the radiating low-frequency ultrasonic transducer with a dry point contact 5, then the radiating low-frequency ultrasonic transducer with dry point contact 5, into the observation well 18 (Fig. 3), to the target depth with a parallel extension of the pipe 10 (Fig. 4), after the emitting low-frequency ultrasonic transducer with dry point contact 5 (Fig. 5) has reached design depth, connecting tee 11 is screwed to pipe 10, connecting tee 11 is connected to pipe 10 at one end, connecting pin 14 is screwed into the second end of connecting tee 11, and a geophysical cable with bayonet connector 9 comes out through the third end, connecting pin 14 is connected to the coupling th 13, which is connected to the tension pin 15, the tension pin 15 is connected to the anchor 16 (Fig. 4), which is monolithic into the anchor plate 17, then by screwing the tension pin 15 (Fig. 5) into the coupling 13, the emitting low-frequency ultrasonic transducer with dry point contact 5 (figure 4) to the wall of the observation borehole 18, until the moment of contact of the emitting low-frequency ultrasonic transducer with dry point contact 5 of the wall of the observation borehole 18. After installing the emitting low-frequency ultrasonic transducer with dry point contact 5 (figure 3) in the design position, the observation well 18 is closed with a composite protective cap 19 to prevent the ingress of debris and atmospheric precipitation into the observation well 18. Next, the geophysical cable with a bayonet connector 9 (figure 2) is connected to the demultiplexer switch 3. This sequence of operations is repeated for all observation wells 18, in the case of installation receiving low-frequency ultrasonic transducers with dry point contact 6 (Fig. 3), a signal amplifier 7 is also installed in observation wells 18, and a geophysical cable with a bayonet connector 9 (Fig. 2) is connected from the receiving low-frequency ultrasonic transducer with dry point contact 6 to switch-multiplexer 4. After installation and connection of all emitting low-frequency ultrasonic transducers with dry point contact 5 with a switch-demultiplexer 3 and receiving low-frequency ultrasonic transducers with dry point contact 6 (Fig. 2) with switch-multiplexer 4, measurements of the propagation time of the longitudinal ultrasonic wave. From a PC with preinstalled software 1, a signal is sent to switch-demultiplexer 3 and switch-multiplexer 4 with the selected number of observation borehole 18, then from the PC, with preinstalled software 1, a device is turned on to measure the propagation time of longitudinal ultrasonic wave 2, from devices for measuring the propagation time of a longitudinal ultrasonic wave 2, an electrical signal, through a demultiplexer switch 3, through a geophysical cable with a bayonet connector 9, is transmitted to a radiating low-frequency ultrasonic transducer with a dry point contact 5 (Fig. 3), emitting a low-frequency transducer with a dry point contact 5, the electrical signal is converted into a longitudinal ultrasonic wave, which passes through the permafrost massif and enters the receiving low-frequency ultrasonic transducer with dry point contact 6, where it is converted from a longitudinal ultrasonic wave into an electric signal, then along a geophysical cable with a bayonet connector 9, the electrical signal, having passed through the signal amplifier 7, and through the switch-multiplexer 4 (Fig. 2) enters the device for measuring the propagation time of the longitudinal ultrasonic wave 2, from where the data is fed to the PC, with preinstalled software 1, where the velocity of propagation of the longitudinal ultrasonic wave is calculated, the dynamic modulus of deformation and the static modulus of soil deformation are calculated, and possible settlements of the foundation of the structure are calculated.

Thus, the use of this method for monitoring the state of an array of permafrost soils, which serve as the basis for the foundations of buildings and structures, allows in an automatic continuous mode to obtain reliable data on changes in the state of an array of permafrost soil and to predict critical settlements of foundations of structures on permafrost soils.

Claims (2)

1. A method for monitoring the state of permafrost soils serving as the basis for the foundations of buildings and structures, including excitation of vibrations, determining the speed and time of arrival of a longitudinal wave passing through a soil massif, characterized in that at the stage of engineering geological surveys, the static modulus of deformation of permafrost soils is determined with taking into account the load from the future structure, after installing the pile foundation at the pile, diametrically, observation wells are drilled, the depth and distance between them are determined based on the results of computer modeling of the stress-strain state of the soil base, while to prevent the collapse of the walls of the wells, concrete lining is installed in them, and concrete anchor slabs are installed on the surface, then low-frequency emitting and receiving ultrasonic transducers with dry point contact are placed in the wells, each transducer has its own serial number, which corresponds to nominal pile, then the soil is sequentially sounded and the time of propagation of the longitudinal wave at each position of the emitting and receiving transducers is determined, the obtained data is transmitted to the PC and the velocity of propagation of the longitudinal ultrasonic wave and the dynamic modulus of deformation of permafrost soils are calculated, after which the correlation dependence between the dynamic modulus is determined deformation and the static modulus of soil deformation, at the stage of operation of the structure, periodic measurements of the propagation time of the longitudinal ultrasonic wave are performed, the dynamic modulus of the soil deformation is calculated, after which the static deformation modulus is recalculated using the previously obtained correlation dependence, the calculation of the estimated settlement of the structure foundation is made and a conclusion is made about the state of the array permafrost. 2. A device for monitoring the state of permafrost soils serving as the basis for the foundations of buildings and structures, including a PC with preinstalled software, a signal amplifier, geophysical cables, a current pulse generator, characterized in that it is additionally equipped with low-frequency receiving and emitting ultrasonic transducers with dry by a point contact, which are connected through switches to a device for measuring the propagation time of a longitudinal ultrasonic wave, switches and a device for measuring the propagation time of a longitudinal ultrasonic wave are connected to a PC via USB cables, low-frequency receiving and emitting ultrasonic transducers with dry point contact are installed in the wells using the device for suspending and providing contact of the transducer with the borehole wall, which includes series-connected, by means of a threaded connection, a tension pin, a coupling, a connecting a pin, a connecting tee and a steel pipe, a clamping angle is rigidly attached to the lower end of the steel pipe, to which a low-frequency receiving or emitting ultrasonic transducer with a dry point contact is attached with the possibility of removability.

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