Establishing the necessary measures for carrying out the activity in security conditions during the execution of work on the Iernut - Chetani highway alignment, Mures county

. The purpose of this work is to establish the regime of methane releases (explosive gas) following the execution of the underpass works of the Sibiu-Pitesti highway in the Curtea de Arge ș -Pitesti sector. INSEMEX Petro ș ani executed during the period 01-04.11.2022 on-site measurements at four highway underpasses with a total length of 843m as well as in the areas adjacent to these underpasses, noting that these underpasses are from wells in operation and are connected to the SRM Meri ș ani Station. Based on the measurements and observations made, the analysis of the elements taken into study, as well as the existing records and documentation, INSEMEX Petro ș ani made the present work.


Monitoring of locations where gas transport pipes have been installed below ground level
In order to carry out in safe conditions the specific activities of installing pipelines below ground level in areas with the risk of forming explosive atmospheres generated by the upward migration of methane along the pipeline routes, it is necessary to ensure the activity of monitoring gas concentrations /1/, /5/.
The complex monitoring system with the help of portable devices, backed by visual observations and the rapid adjustment of preventive measures according to local conditions, is recommended.
The monitoring system with the help of portable devices is justified by the fact that pipeline routes are made over long distances.Also, pipeline routes cross isolated areas, sometimes difficult to access and without basic infrastructure (current electricity, telecommunications system, etc.) /2/, /6/.
The monitoring system must be applied linearly, continuously or discontinuously on the pipeline route alignment.

Monitoring of gas transport pipeline alignments
The monitoring operation on the alignment of the gas transport pipelines is carried out after the execution of the works and their pressurization as follows /4/ : -Periodic monitoring in normal mode of the potentially explosive atmosphere, by determining methane concentrations on the soil surface along the pipeline route, with the help of portable devices, during the entire period of their exploitation; -Intensive daily monitoring with normal cadence of the potentially explosive atmosphere in areas where low gas concentrations are detected on the soil surface (in the order of ppm) on the pipeline route alignment; -Daily intensive high-frequency monitoring of the potentially explosive atmosphere in areas where high gas concentrations are detected on the ground surface (of the order of tenths of a percent) along the pipeline route.The initial monitoring was carried out between 01.11.2022 and 04.11.2022.During the execution of the monitoring, the evolution of the following gases was observed at the soil surface: -Methane ( CH4 ) -Oxygen ( O2 ) -Carbon monoxide ( CO ) -Carbon dioxide ( CO2 ) -Hydrogen sulfide (H2S).
Gas concentrations measured at the ground surface along the pipeline routes showed the following variation: ▪ CH4, the values were between 0.0 and 0.0006% vol.; ▪ CO, had the value of 0% ppm.; ▪ O2, had the value of 20.93 % vol.; ▪ CO2, the values were between 0.04 and 0.06% vol.▪ H2S, the concentration of hydrogen sulphide had the value of 0.000% vol.
It is mentioned that where concentrations of hydrocarbons were detected, they had low concentrations, were highlighted in the underpass areas of the roadway and were due to fuel losses from the means of transport /3/, /7/.
At the same time, the specific measurements took place under the following conditions; -the temperature was between 13.0 and 22.3 C o ; -the humidity was between 46.6 and 69.6 %; -the barometric pressure was between 976 and 982 hPa.
The results of the monitoring activity on the alignment of the four gas transport pipeline sections are shown in tables 1-4

Conclusions
In order to carry out research on gas dynamics through soils, a test stand was designed, with which methane gas can be injected into the soil and the concentration of the gas can be measured at defined points at certain distances from the injection site.The test stand consists of a center for measuring concentrations OLDHAM MX52 16-channel methane.The measuring center was equipped with 16 methane gas concentration measuring transducers, which work on the katharometer principle and can measure concentrations between 0% and 100% volume and connected to a computer.
The tests were carried out several series of tests to form a basis of statistical-mathematical data, to substantiate a mathematical model of gas migration in the soil.Diagrams of gas concentrations were obtained, depending on the time in which the gas emanated through the soil was detected by the transducer cell.
The results of the measurements were the basis for the elaboration of the map of migration isolines a of methane gas through the soil, using the detection times of the concentration increase at the points of measurement, using the interpolation method between the moment when the methane gas has diffused to each detection head, located in the holes made in the ground.Was identified the analytical form of the time function related to the distances traveled by the gas migrated and its geometric image (regression curve).
Porosity can influence the extent of accumulation and delay phenomena of propagation, highlighting a migration effect only at the "source" and not at the "receiver".The result of the research materialized in a mathematical model of the phenomenon migration of the migration phenomenon, which includes two components: accumulation and migration as an effect of the pressure difference.
The mathematical formula highlights the mostly non-linear dependence of apparent permeability, relative to the pressure drop.The main limitation of the model is that it does not consider the vertical component of gas migration.
Following the analysis of the measurement results, it was found that the properties soil hydraulics, established for conducting the experiments, are not homogeneous.
Following the measurements and observations on the alignment of the Four underground gas pipeline sections, it is concluded that the highest methane accumulations occurred in the underpass areas of the roadway.
During the execution of the initial monitoring the methane concentrations were insignificant with values between 0.0003 and 0.0006% vol.
During the execution of the initial monitoring, no carbon monoxide concentrations were detected.
During the execution of the initial monitoring, carbon dioxide concentrations ranging from 0.04 to 0.06 were detected.The measured carbon dioxide is specific to atmospheric air.
During the execution of the initial monitoring, normal oxygen concentrations of 20.93 % vol.were detected.
During the execution of the initial monitoring, no concentrations of hydrogen sulfide were detected.The specific measurements took place under the following conditions; -the temperature was between 13.0 and 22.3 C 0 ; -the humidity was between 46.6 and 69.6%; -the barometric pressure was between 976 and 982 hPa.
The measurements carried out by INCD INSEMEX Petroșani regarding the initial monitoring were carried out on the alignment of three sections of gas transport pipelines in the Curtea de Argeș area, namely: Section 1 Km.101 (Dacian Petroleum) with the length of L= 318m, (Figure no.1.) Section 2 Km 101 +700m (Dacian PETROM) with the length of L=203 m (Figure no.2.) Section 3 Km 103 +600m (Petrom) with the length of L=201 m. (Figure no.3.) Section 4 Km 104 (Dacian PETROM) with the length of L=121m.(Figure no.4.)