What should be included in the foundation pit monitoring program

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Monitoring of building foundation pit engineering.

The scheme includes: 1. Project overview.

2. Geotechnical engineering conditions of the construction site and the surrounding environmental conditions of the foundation pit.

3. Purpose and basis of monitoring.

4. Monitoring content and items.

5. Layout and protection of reference points and monitoring points.

6. Monitoring method and accuracy.

7. Monitoring period and monitoring frequency.

8. Monitoring alarms and monitoring measures under abnormal conditions.

9. Monitor data processing and information feedback.

10. Staffing for monitoring.

11. Monitoring instruments and equipment and verification requirements.

12. Operational safety and other management systems.

Foundation pit overview, detection basis, workload, hydrogeology and engineering geology, monitoring methods include point layout and monitoring methods, monitoring frequency, monitoring alarm value, information feedback mechanism, emergency treatment, on-site operation safety.

Horizontal displacement monitoring, vertical displacement monitoring, deep displacement monitoring, crack monitoring, internal force monitoring of supporting structures, earth pressure monitoring, water pressure monitoring, groundwater level, rainfall, etc.

Detection system architecture:

The foundation pit monitoring and early warning system is mainly composed of integrated monitoring station equipment, on-site communication equipment, user-built monitoring and early warning cloud service platform based on Internet of Things technology and cloud computing, user terminal information equipment and application software.

Monitoring programme implementation:

2. Vertical displacement monitoring, using laser rangefinder and level to complete the collection and issuance of surface vertical displacement and deformation monitoring data.

3. Deep displacement monitoring, the deep displacement monitor is used to complete the collection and issuance of deep displacement deformation monitoring data, including small displacement in the early stage of deformation and large displacement deformation in the middle and late stages.

4. Crack monitoring: The integrated pull line surface displacement monitor and laser rangefinder are used to complete the collection and issuance of crack deformation monitoring data.

5. The internal force monitoring of the supporting structure is carried out by using dynamometer, strain gauge and stress gauge to complete the collection and issuance of the internal force monitoring data of the supporting structure.

6. Earth pressure monitoring, using earth pressure gauge to complete the mining and issuance of monitoring data of internal pressure change in rock and soil.

7. Water pressure monitoring porosity.

8. Groundwater level monitoring, using groundwater level gauge to complete the collection and issuance of groundwater level change monitoring data.

9. The internal force monitoring of anchors and soil nails is carried out by using dynamometers, strain gauges and stress gauges to complete the collection and issuance of internal force monitoring data of anchors and soil nails.

10. Rainfall monitoring: Use a tipping bucket rainfall monitor or infrared rain gauge to complete the collection and issuance of rainfall change monitoring data in the area.

The monitoring program of building foundation pit engineering includes: 1. Project overview. 2. Geotechnical engineering conditions of the construction site and the surrounding environmental conditions of the foundation pit.

3. Purpose and basis of monitoring. 4. Monitoring content and items. 5. Layout and protection of reference points and monitoring points.

6. Monitoring method and accuracy. 7. Monitoring period and monitoring frequency. 8. Monitoring alarms and monitoring measures under abnormal conditions.

9. Monitor data processing and information feedback. 10. Staffing for monitoring. 11. Monitoring instruments and equipment and verification requirements.

12. Operational safety and other management systems.

The content of foundation pit engineering monitoring does not include the following:

The content of foundation pit engineering monitoring does not include each warning value, which should be based on the allowable change in unit time.

1. Overview of the corresponding engineering, meteorology and surrounding environment during the monitoring period;

2. The layout of the monitoring items and measurement points during the monitoring period;

3. The process curve of collation, statistics and monitoring results of various monitoring data;

4. Analysis, evaluation and development of changes in the monitoring values of each monitoring project**;

5. Relevant design and construction suggestions.

According to the enclosure form of the foundation pit, the excavation depth of the foundation pit and the surrounding environment, etc., the foundation pit monitoring must involve the following aspects:

The content of foundation pit monitoring.

Horizontal displacement monitoring of deep soil: horizontal displacement monitoring points are set along the soil depth within the scope of the soil nailing wall, and the horizontal displacement of each point of the soil depth in the excavation process of the foundation pit is observed.

Horizontal displacement of the retaining pileThe horizontal displacement of the retaining pile is carried out by the inclination hole embedded in the enclosure pile.

Internal force monitoring of the support system: The reinforcement stress gauge is buried on the main reinforcement of the main stress support to observe the internal force change of the support during the excavation of the foundation pit.

Groundwater level monitoring: The measuring holes of groundwater level monitoring are covered with plastic pads with water filter holes, and a total of 19 water level monitoring holes are arranged inside and outside the foundation pit.

The foundation pit is close to the settlement observation point of buildings, columns and municipal facilities.

1. Horizontal displacement monitoring.

When determining the horizontal displacement in a specific direction, the line-of-sight method, the small angle method, the projection point method, etc. can be used; When measuring the horizontal displacement of the monitoring point in any direction, the distribution of the monitoring point can be visualized, and the forward rendezvous method, free station method, polar coordinate method, etc. are adopted.

When the datum point is far away from the foundation pit, the GPS measurement method or the comprehensive measurement method combining trigonometry, trilateral, corner measurement and reference line method can be adopted. When the monitoring accuracy is relatively high, the micro-deformation measurement radar can be used for automatic all-weather real-time monitoring.

2. Vertical displacement monitoring.

Vertical displacement monitoring can be done using methods such as geometric leveling or hydrostatic leveling. The uplift (rebound) at the bottom of the pit should be monitored by setting a rebound monitoring mark, using geometric level and supporting equipment to transmit elevation.

The vertical displacement monitoring accuracy of the metal pole or steel ruler that transmits the elevation should be corrected for temperature, ruler length and tensile force, etc., and the vertical displacement monitoring accuracy of the foundation pit retaining wall (slope), the surface and the column behind the wall should be determined according to the vertical displacement alarm value.

3. Deep horizontal displacement monitoring.

The monitoring of the deep horizontal displacement of the enclosure wall or the soil around the pit should adopt the method of embedding the inclinometer tube in the wall or soil and observing the horizontal displacement at each depth through the inclinometer.

4. Tilt monitoring.

The tilt monitoring of the building should measure the horizontal displacement and height difference of the top of the monitored object relative to the bottom, and record and calculate the inclination, inclination direction and inclination rate of the monitored object respectively. According to different on-site observation conditions and requirements, the projection point method, horizontal angle method, forward intersection method, normal perpendicular line method, differential settlement method, etc. should be selected.

5. Crack monitoring.

Crack monitoring should include the location, strike, length, width, and degree of change of the fracture and, if necessary, depth. The number of cracks to be monitored should be determined as needed, and the main or large cracks should be monitored.

6. Monitoring of the internal force of the supporting structure.

The change of internal forces of the supporting structure during the excavation of the pit can be measured by installing strain gauges or stress gauges inside or on the surface of the structure. For reinforced concrete supports, it is advisable to use a reinforcement stress gauge (reinforcement meter) or a concrete strain gauge for measurement; For steel structure support, it is advisable to use an axial force gauge for measurement.

Answer]: a, b, c

According to Article 13 of the Code for Geotechnical Investigation (GB 50021-2001) (2009 Collapse Rough Comic Edition). 2.4, the monitoring program of the foundation pit project should be determined according to the site conditions and the construction design of the excavation support, and should include:

deformation of the supporting structure; deformation of the ground around the foundation pit; deformation of adjacent works and underground facilities; groundwater table; Seepage and leakage, water bubbling, scouring, pipe gushing, etc.

Answer]: a, b, c

2020 edition of textbook p215

This question mainly examines the following: foundation pit engineering inspection and rough belt measurement, foundation pit engineering testing includes supporting structure monitoring and surrounding environment monitoring (deformation monitoring of the terrain outside the pit).