Construction processes are often influenced by external factors that cause accidents. To control them, special forecasting and complex analysis systems are being developed, which makes it possible to prevent such threats by taking appropriate measures or changing the tactics of working activities. One of the central areas of such control is geotechnical monitoring (GTM), through which it is possible to predict and even manage the state of the target object in terms of its interaction with factors of a negative impact of a natural nature.
GTM concept
GTM is understood as a set of measures related to monitoring the state of structures of a facility under construction or reconstruction. Special attention during the control is given to the base of the bearing array and surrounding structures. Technological data of workare organized on the basis of observation posts located both in the construction zone and outside it in laboratory conditions. At the same time, geotechnical monitoring of buildings and structures is not limited to monitoring the state of the target object during its construction. Even at the stage of project development, it may be possible to integrate the well intervention system into a set of maintenance activities during the operation of the facility.
GTM Goals
The main goals of geotechnical surveillance include ensuring safety during the construction and operation of the controlled structure, as well as the formation of a base of indicators by which it is possible to assess the degree of its reliability. This applies not only to facilities under construction and put into operation, but also to works carried out as part of repairs and reconstruction. The goals of geotechnical monitoring are achieved due to the timely detection of processes of change in the studied parameters. Both the characteristics of the structure and the properties of the foundation soil are taken into account.
GTM Tasks
The following tasks are solved in the process of geotechnical control:
- Regular fixation of changes in the parameters of the geological massif and structures located on it.
- Timely detection of deviations in parameters, as well as any changes that may disrupt the expected trends in the course of ongoing work.
- Assessment of risks that entail identified deviations of controlled parameters.
- Set the reasons for committed changes.
- Based on the results of geotechnical monitoring of buildings and structures, a set of measures is being developed to help prevent and eliminate further negative processes.
Use of geological and technical measures in construction
GTM is connected to the construction processes at the stage of the zero cycle during geodetic surveys and land works. In particular, this applies to the soil base, foundation and basic load-bearing structures. With regard to construction pits, monitoring is carried out in relation to the enclosing structures, which exclude the risks of collapse. Surveys also affect underground facilities - communications, engineering structures and tunnels. As part of geotechnical monitoring in construction, factors that affect the object being constructed or reconstructed are taken into account. Both potentially dangerous geological processes (subsidence, landslides, suffusion) and dynamic impacts, the sources of which are directly construction works, are taken into account.
GTO in soil control
When carrying out GTM, the state of the soil massif, its behavior and possible changes associated with the loads exerted during construction are assessed. In relation to organic soils, the following characteristics are analyzed:
- Deformation of the base under the foundation of the structure under construction.
- Horizontal offset groundformation depth.
- Groundwater level.
- Hydrodynamic pressure that can occur in water-saturated organomineral and organic soils due to the effect of additional load.
- The nature of the change in the physical and mechanical properties of the array.
In relation to bulk soils, geotechnical monitoring provides for the following measurements of controlled parameters:
- Degree of settlement that occurs due to self-compacting of newly dumped and existing soils.
- Load from the foundation platform of the structure under construction.
- Loads from massive building materials and equipment placed on site.
- Basic characteristics of bulk soils.
Scope of work on geological and technical measures
According to the regulations, geotechnical monitoring includes the following activities:
- Development of a program and project to control the target object. The list, volumes and methods of operations are determined based on the geological surveys carried out at the construction site.
- Determining the timing and frequency of monitoring operations. The schedule is set depending on the planned duration of construction, taking into account land works and operations related to the elimination of identified negative impact factors.
- Determination of controlled parameters. In this case, both local geological conditions and the characteristics of the facility under construction are taken into account, includingincluding the level of his responsibility.
- Processing the received data and compiling a report, on the basis of which measures are taken to reduce the recorded risks.
Geotechnical monitoring project
During the development of the geological and technical measures project, a set of design solutions is formed that could ensure a minimum degree of impact on the facility from negative impact factors. This takes into account not only the effectiveness of the methods, but also the economic feasibility of their application. A technological map of the production of analytical measures is compiled, optimal methods for surveying the territory are selected, taking into account the climatic and geophysical parameters of a particular region. In the project of geotechnical monitoring of the construction of a building, requirements for environmental safety are also prescribed, which can manifest itself in the form of restrictions on the use of certain methods of influencing the natural landscape, in particular. Ultimately, the developers present a comprehensive set of measures with a timetable for their implementation and the possibility of adjustment depending on the influence of external factors.
Geotechnical forecasting
Forecasting plays an important role in the well intervention complex. This toolkit is used in the design of foundations, underground parts of buildings and foundations. A forecast of this kind is understood as an assessment of the possible impact of the construction process on the state and characteristics of the soil massif. Such activities are also necessary fordevelopment of projects for laying engineering communications located in a built-up area. As the initial data for geotechnical monitoring with prediction, the parameters of the displacements of the enclosing structures are used, and the nature of the stress-strain effect on the soil from the erected structure is also taken into account. In calculations, numerical and analytical methods are used to assess possible changes. In predicting additional deformations that may be caused by vertical loads from the object under construction, it is allowed to use the design scheme in the form of a linearly deformable half-space.
GTM methods
To implement monitoring, various technological approaches are used, including geodetic, visual, vibrometric, parametric, etc. The simplest and most common group of methods involves visual-instrumental control, in which an object is inspected with subsequent removal of the necessary measurements. In particular, geotechnical monitoring of buildings with visual control captures the development of cracks in structures, deviations in the position of ceilings and walls, damage characteristics, etc. Geophysical monitoring methods offer a different approach to monitoring. In this case, a complex of engineering-geological and hydrogeological research activities is carried out, which may not affect the parameters of the construction site at all, but they fully study the properties of the local soil and its physical characteristics, taking into account the levels of groundwater.
Tools for recording geological and technical measures
Practically all methods of modern geotechnical control involve the use of technical means and devices to accurately determine the controlled indicators. It can be a simple measuring instrument like a level or a tape measure, or electronic devices that automatically fix target parameters - not only physical and geometric, but also microclimatic ones. For example, to measure the settlement and heel of a building or its individual structures, complex geotechnical monitoring systems are used that capture parametric data thanks to pre-installed sensors and markers. For a certain period of time, readings are taken from them, allowing you to track the dynamics of the progression of a roll or crack opening. But for forecasting, such indicators as the temperature regime with the dynamics of drops, humidity coefficients, pressure levels, etc. are also significant. For these and other measurement operations, piezometers, inclinometers, mass doses, dynamometers, strain gauges and other devices are used.
Geotechnical monitoring programs
After fixing the controlled values, geotechnicians enter specific data into a log to generate a report. Further, a comprehensive analysis of the information received is carried out in order to develop protective measures, if necessary. To solve such problems, special geotechnical monitoring programs are used, among which the following solutions can be noted:
- TUN2 system. A simple and easy-to-use software tool designed to perform static analysis of underground structures.
- POLUPROM program. The algorithm of this system allows you to perform the calculation of bar structures and structures, offering the possibility of modeling lines of influence. Also, this program is used as a universal engineering calculator.
- Midas complex. A Korean multifunctional product that performs basic geotechnical data processing operations, as well as specialized calculations in the field of tunneling.
Conclusion
Geotechnics in construction in its primitive form has been used since ancient times, when people tried to foresee the risks of impacts from natural phenomena when constructing housing. Nowadays, we can talk about multilateral and high-tech geotechnical monitoring, which allows you to identify, record, analyze and develop means to eliminate both existing and possible threats during the construction or operation of various facilities. At the same time, one should not consider the methods of such control only as a means of one-sided reporting of problems. Modern well intervention methods are becoming more interactive, which gives grounds to consider them both as a means of ensuring safety and as a tool for finding optimal economic solutions for the implementation of a project.
