Monitoring instruments, equipment and elements shall meet the following requirements: meet the requirements of observation accuracy and range, and have good stability and reliability; It shall be calibrated or calibrated, and the verification records and calibration data shall be complete, and shall be used within the specified calibration validity period; 3 during the monitoring process, the maintenance and detection of monitoring instruments and equipment and the inspection of monitoring elements shall be carried out regularly.
The monitoring and early warning value shall be determined by the foundation pit engineering designer.
When rock foundation pit and soil rock combined foundation pit are excavated by blasting, the particle vibration velocity or acceleration of buildings (structures), bridges, roads, pipelines and other protected objects within the influence range of blasting vibration shall be monitored.
At the end of monitoring, the monitoring unit shall provide the monitoring summary report to the owner and file the following data in volumes: 1.
When determining the early warning value of buildings, pipelines and roads around the foundation pit, it shall be ensured that the original settlement or deformation value and the additional settlement or deformation value caused by foundation pit excavation and precipitation shall not exceed the allowable maximum settlement or deformation value.
For collapsible loess and expansive soil foundation pit, when the soil on the pit wall is likely to be soaked, the soil moisture content should be monitored.
The foundation pit engineering for automatic monitoring shall also comply with the following provisions: the automatic monitoring system shall include monitoring instruments and equipment, automatic data acquisition system, transmission system, storage management system and real-time release system; The accuracy and range of automatic monitoring instruments and equipment shall meet the engineering requirements; The automatic monitoring system shall be able to carry out automatic early warning or fault display in case of abnormal data.
The monitoring unit shall timely process and analyze the monitoring data, and timely feed back the monitoring results and evaluation to the owner and relevant units.
The owner and the general contractor shall assist the monitoring unit to protect the monitoring facilities.
The initial value of monitoring items shall be measured before relevant construction procedures, and the average value of stable values observed for at least 3 consecutive times shall be taken.
During the on-site patrol, the following phenomena and their development shall be checked: during the construction and service life of the foundation pit project, a specially assigned person shall carry out patrol inspection every day.
Monitoring summary report.
Monitoring scheme; 2.
The on-site monitoring of foundation pit engineering shall adopt the method of combining instrument monitoring and on-site patrol inspection.
In case of any of the following situations, a danger alarm must be given immediately, and relevant parties shall be notified to take emergency measures for the foundation pit support structure and the surrounding environmental protection objects.
The monitoring unit shall prepare a monitoring scheme, which shall be approved by the construction party and the designer.
The setting of the datum point and working base point of the deformation monitoring network shall comply with the following provisions: the datum point shall be located outside the construction influence range without disturbance, and the datum point shall be stable and reliable; The working base point shall be selected at a relatively stable and convenient position.
When the monitoring data reaches the monitoring early warning value, early warning shall be given immediately, and relevant parties shall be notified to analyze the causes in time and take corresponding measures.
The monitoring unit shall implement monitoring according to the monitoring plan.
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In case of major changes in the design or construction of foundation pit engineering, the monitoring unit shall study with the owner and relevant units and adjust the monitoring scheme in time.
Deformation monitoring early warning value shall include cumulative change early warning value and change rate early warning value of monitoring items.
Layout and acceptance records of datum points and monitoring points; 3.
The horizontal displacement of the rock mass at the rock socketed part of the retaining pile shall be monitored.
The monitoring items for the soil rock combined foundation pit project shall be selected according to the design safety grade of the foundation pit, rock mass quality, soil rock distribution, soil rock interface and groundwater conditions, support form and surrounding environmental deformation control requirements.
Before the construction of foundation pit works, the construction party shall entrust a third party with corresponding ability to carry out on-site monitoring of foundation pit works.
Monitoring scope: the monitoring items shall match the engineering design and construction scheme; key observation shall be carried out for the key parts of the monitoring object; The selection of monitoring items shall be conducive to the formation of a mutually complementary and verified monitoring system.
Periodic monitoring report; 4.
The monitoring and early warning value of foundation pit and supporting structure shall be determined according to the design safety level of foundation pit, engineering geological conditions, design calculation results, local engineering experience and other factors; When there is no local engineering experience, the soil foundation pit can be determined according to table 8.0.4 in the technical standard for monitoring of building foundation pit engineering (gb50497-2019).
The selection of monitoring methods should be comprehensively determined according to monitoring requirements, site conditions, local experience, method applicability and other factors.
The monitoring and early warning value shall meet the deformation and safety control requirements of foundation pit support structure and surrounding environment.
When there are subways, tunnels or other buildings and facilities with special requirements for displacement around the foundation pit, the monitoring items shall be determined through consultation with relevant management departments or units.
During the monitoring period, the monitoring party shall protect the monitoring facilities.
The patrol inspection of foundation pit engineering should include the following contents: monitoring methods and accuracy requirements.
The monitoring scope of foundation pit engineering shall be comprehensively determined according to the design depth of foundation pit, geological conditions, surrounding environment, support structure type and construction method; When using construction precipitation, the influence range of precipitation and land settlement shall also be considered.
Automatic monitoring should be implemented when the following provisions are met: monitoring items requiring high-frequency or continuous real-time observation; Monitoring items that are not allowed or impossible to be observed manually under environmental conditions.
When the intervisibility condition is good and the distance is close, the base point should be directly used as the working base point; Networking and joint measurement shall be conducted between the working base point and the base point.
The deformation and safety control of foundation pit supporting structure and surrounding environment shall comply with the following provisions: ensure the stability of foundation pit; Ensure the normal construction of underground structures; The deformation caused by the surrounding existing buildings shall not exceed the requirements of relevant technical standards or affect their normal use; Ensure the normal use of surrounding roads, pipelines and facilities; Meet the technical requirements of special environment.
Basically, the design documents of foundation pit engineering shall specify the monitoring scope, monitoring items, layout of measuring points, monitoring frequency and monitoring early warning value.
Daily patrol during the construction of the supporting structure, foundation pit excavation and the service life of the supporting structure, the conditions of the supporting structure and the surrounding environment shall be inspected at any time.
If necessary, it shall consult with relevant management units involved in the surrounding environment of the foundation pit before implementation.
