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Abstract

Contents

Introduction

The actual problem of the domestic road industry is rutting due to the accumulation of residual (plastic) deformations in the structural layers. road pavement and especially the working soil layer of the subgrade. The most important indicator of the subgrade, which has a significant impact on design decisions and operational indicators of the work of the pavement, - the density of the soil of the working layer (1.5 m from the top of the pavement). In this regard, the question arises today justification of the need to increase the degree of compaction soils and ways to achieve high density indicators. As a solution for moisture measurement soil on various sections of the road, it is proposed to use a soil moisture data collection system based on a microcontroller for subsequent analysis of the information received.

The quality of compaction of the subgrade determines the strength and deformability of soils, of which its structure was built. As a result of properly designed pavement, soils work in the compaction stage, undergoing permanent deformations, which are relative to the number of applied loads are damped and are linearly related to voltages. Thus, the degree of soil compaction affects the evenness of the coating, to which the standard puts forward strict requirements, and in the work of specialists, the restrictions on the depth of irregularities are even more stringent. Evennesscoatings determine the most important consumer properties of automobiles. The development of unevenness on the surface of the coating is one of the main factors, contributing to the deterioration of the operational condition of the road. From the point of view of mechanics, unevenness is caused by the accumulation of unevenly distributed irreversible deformations in various layers of the road structure. This process is observed for a sufficiently long period of time, since one-time impacts vehicles, as a rule, do not lead to the formation of zones of irreversible deformations.

1. Relevance of the topic

Moisture is an important characteristic of the state of the soil and is taken into account when determining many indicators of soil properties (modulus of elasticity, plasticity, stickiness, etc.) [1]. Other characteristics depend on soil moisture, such as its bearing capacity and density. It is the soil moisture that renders perhaps the most significant influence on the method of soil development and on the predisposition of soils to compaction operations. The durability and operational condition of the road is significantly influenced by the temperature-humidity regime of the soil of the subgrade. As you know, a change in moisture content, first of all, affects the ability of the soil to withstand the design loads provided for at the design stage. The increased moisture content of the underlying soil layers reduces both the strength and deformation characteristics, and significantly changes its rheological and dynamic properties. The most dangerous consequences can be caused by high humidity, close to the humidity at the fluidity limit. In this case, there is a sharp decrease its strength and deformation characteristics, the ability to resist the dynamic impact of vehicles is significantly reduced, which leads to accelerated process of accumulation of residual deformations [2]. Obtaining the dependence of the magnitude and rate of accumulation of residual deformations on humidity and acting on The load root would allow a more detailed study of the influence of weather and climatic factors on the subgrade soil and the road structure as a whole.

The durability and operational condition of the road is significantly influenced by the temperature-humidity regime of the soil of the subgrade [3]. As known, the change in moisture, first of all, affects the ability of the soil to withstand the calculated loads provided for at the design stage. High humidity underlying soil layers reduces both the strength and deformation characteristics, and significantly changes its rheological and dynamic properties. Most hazardous consequences can be caused by high humidity, close to humidity at the fluidity limit [4]. In this case, there is a sharp decrease in its strength and deformation characteristics, the ability to resist the dynamic impact of vehicles is significantly reduced, which leads to an accelerated process accumulation of residual deformations. Obtaining the dependence of the magnitude and rate of accumulation of residual deformations on moisture and the load acting on the soil would allow study in more detail the influence of weather and climatic factors on the subgrade soil and the road structure as a whole.

As an example, Fig. 1 shows a graph of tests under the influence of a dynamic load of soil samples made of loam with a plasticity number Iр = 13 with different moisture content from 0.53 to 0.84 Wt, obtained after water saturation with compaction coefficients of 0.98 [5].

pic1

Picture 1.1 – Accumulation graph of residual deformations depending on soil moisture

At present, the main requirements for the technology of erecting road beds for highways and for soils used in road construction. A number of requirements are imposed on soils permitted for use in road construction, the most significant of which is the compaction coefficient. The required value of the coefficient of soil compaction of the subgrade of the road-climatic zones is 0.98 [6]; while in the non-flooded part of the embankment it is allowed use soil with a compaction coefficient of 0.95, and in the working layer of the excavation below the seasonal freezing zone - 0.95–0.92.

Small, but at the same time, permissible values of the compaction coefficient can become the reasons for the occurrence of processes of uneven compaction of soils, which, in turn, they influence the rutting processes. If the value of the maximum permissible residual deformation in soil samples is exceeded for the working layer of the subgrade, the soil compaction coefficient is adjusted upward in order to reduce the speed accumulation of moisture in the ground canvas in the design period and thereby reduce its design moisture content in accordance with the previously obtained design moisture content of cohesive soils, depending on compaction coefficient and type of terrain according to moisture conditions [7]. In this regard, it is necessary to clarify the maximum and minimum values ??of moisture in the calculated period for different climatic conditions. The most effective such studies are seen with the use of special sensors capable of automatic mode to register changes in moisture content in the soil of the subgrade at a given frequency.

2.Purpose and objectives of the study, planned results

The aim of the study is to develop a system for studying the effect of soil moisture on the deformation of the subgrade, to detect the need for strengthening work.

The main objectives of the research:

  1. Analysis of methods for measuring soil moisture content of the roadbed
  2. Assessment of economic losses as a result of not carried out strengthening works of the land bed
  3. Analysis of the conducted studies of the magnitude of the accumulation of residual deformations in soil samples
  4. Development of a soil moisture monitoring system based on a microcontroller.
  5. Investigation of the efficiency of a system providing data on soil moisture content of the roadbed of a highway

Object of research : System for researching soil moisture data.

Subject of research : Generation of data allowing to increase the service life of highways

For an experimental assessment of the theoretical results obtained and the formation of the foundation for further research, as practical results it is planned development of an autonomous soil moisture monitoring system based on an Arduino microcontroller and an interface program in the Windows operating system with the following properties:

  1. Availability of our own system with a sensor for monitoring soil moisture.
  2. Releasing a C sketch program for a microcontroller that processes data received from a sensor.
  3. Implementation of a C #-based program that provides an interface for interacting with the received data.
  4. It is possible to generate an Excel report for saving, formatting and further work with data.

3. Research & Development Overview

Since soil strengthening is a fundamentally new approach to the design of road and airfield clothing, based on the study of interaction features of working bodies of machines with compacted material, there is a justification of the optimal parameters and modes of compaction of various types of soils, hardened materials and asphalt concrete mixtures. given in the Federal Road Agency of the Ministry of Transport of the Russian Federation [8]. A lot of work is devoted to the implementation of systems based on a microcontroller, as well as the development of programs based on the C, C # languages, mainly by representatives of the Western school [9].

4. Arduino-based research system implementation

Based on the data presented earlier, it was concluded that it is possible to use a system based on a moisture sensor and a microcontroller for long-term monitoring of soil moisture in an earthen slab under real road conditions.

As the investigated function, we take the van der Pol equation, the amplitude of which decays in time:

For optimal system performance and correct functionality, you need to select hardware that will match the task at hand. The following hardware is offered for the soil data collector: Arduino Nano board based on ATmega328P, FC-28 moisture sensor module [10].

Принцип работы устройства
Picture 4.1 – The principle of operation of the device (animation: 8 frames, cycles repetitions: 30, 279 kilobytes)

These elements have a number of advantages: low cost compared to existing analogs, in the form of a Raspberry Pi mini computer or an Aquapulse humidity sensor. AP 4008, availability, ease of use in the development and construction of such systems.

For microcontroller, it is necessary to develop software that will collect information from the sensor and send data to the server. Therefore, for the server, which is supposed to be a personal computer, it is necessary to implement a database and an application that allows you to work with the available information. The software will be implemented in C, C # programming languages.

To develop a program The microcontroller is supposed to use the Arduino IDE development environment. The Arduino program is called sketch and has the extension "* .ino". This is the code that is loaded and executed on the Arduino platform.

As a programming language for developing a client application working with the database, it is assumed to use the C # language, since Visual C # provides an advanced code editor, convenient user interface designers, an integrated debugger, and many other tools that simplify the development of C # applications for the platform. To store data, you can use a .json file and its corresponding Json serialization, which is textual and lightweight. This approach makes it quite easy to save the data, and also view it if necessary.

To create the graphical part of the application, you can use the Windows Forms technology due to its simplicity and convenience [11]. An example of the user interface is shown in Figure 2

pic2

Picture 4.2 – Sample GUI

Сonclusions

The proposed system allows collecting data on the soil moisture content of the roadbed of a motor road for specified time intervals with high accuracy. In the course of the study, it was established the need to use a system based on a microcontroller and a humidity sensor for data collection, which will determine the compaction coefficient required for a specific section of the roadbed of an auto-mobile road. Such a system will avoid waterlogging of the soil and how consequence of the premature destruction of the road, and will also make it possible to collect and store data for their further use in various kind of research.

As a result of studying the effect of soil moisture on the accumulation of residual deformations under the influence of dynamic loads, it was found that the total the magnitude of residual deformations and the intensity of its accumulation in soil samples significantly depend on moisture. Analysis of the obtained data on the intensity of capillary water saturation showed that the change in the moisture content of cohesive soils significantly depends on the compaction coefficient (density)the soil, i.e. the higher the compaction coefficient of the soil, the less it is subject to capillary water saturation. Thus, the need to increase the compaction coefficient by sections of the road with a high probability of waterlogging of earthen soil canvases in the billing period.

References

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  2. Ковнацкий Б.Д. Разработка системы исследования влияния влажности грунта на деформацию земляного полотна / Ковнацкий Б.Д., Николаенко Д.В.// Сборник научных трудов III научно-практической конференции (студенческая секция) Программная инженерия: методы и технологии разработки информационновычислительных систем (ПИИВС-2020). — Донецк: ДОННТУ, 2020. — с. 162-165.
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