1. Basis for compilation.
1.1 Relevant national, industry and local norms and procedures.
1.2. Relevant design drawings
1.3 Safety management regulatory documents
1.4 Miscellaneous
2. Project overview
2.1 General Overview
2.2 Design Overview
The underground connecting lanes of the Urumqi Wanda Plaza project are designed with three underground connecting lanes, and the underground connecting lanes are numbered for easy identification.
Among them, 1, the underground connecting driveway, from the large commercial basement through Wanshoushan Street, leads to the basement of the five-star hotel; 2. The underground connecting driveway leads from the underground garage of plot 2 through Yuntaishan Street to the underground garage of plot 3; 3. The underground connecting driveway leads from the basement of the Grade A office building through Yuntaishan Street to the underground garage of Lot 3; For details, see schematic diagram 2-1 of the location of the connected lane.
2.3 Overview of the engineering task
The settlement measurement design of the underground connecting lane of Urumqi Wanda Plaza provides the elevation according to the general plan design, and its coordinates are the urban coordinate system of Urumqi City, and the elevation is the national elevation datum in 1985. According to the actual site, due to the complexity of the underground municipal pipeline of Wanshoushan Street, it is planned that 1 connecting lane will be constructed by underground excavation, and 2 underground connecting lane will be constructed by excavation. Therefore, according to the on-site survey, the existing topography of the survey area in the topographic map has not changed basically, and it can be used for the design of settlement datum points and observation points.
Considering the actual site, the construction site and the construction personnel are more complex, in order to ensure the stability and safety of the observation point, 1 underground connecting lane adopts the construction of the underground excavation mode, and the design lays four observation points in the center of the road, and three observation points are respectively arranged on both sides of it. 2 underground connecting lane to take a large excavation mode of construction, design on both sides of the foundation pit slope respectively laid three observation points, and after the opening, the bare leakage of water supply pipe and power pipe support foundation laying observation point, in view of the underground connecting lane around the adjacent buildings, so do not consider the surrounding building deformation settlement observation problem, only consider the monitoring of the connected lane itself in the process of dark excavation or excavation support and the construction stage (before the completion of the foundation pit backfill) of the foundation pit deformation observation displacement, stability.
3. Construction organization chart
4. Layout of observation points for underground connected lanes.
5. Construction preparation
5.1 Technical Preparation
1) According to the specification, the settlement observation should be able to observe the uniform settlement and uneven settlement of more than 2mm, to achieve such monitoring accuracy, only the method of precision geometric level measurement, that is, the use of precision level and supporting precision level and level pad, ruler frame, etc., according to the (three, four) level of level measurement requirements, in the form of round-trip attached level route or closed level route, regularly from the reference level point to the settlement observation point around the foundation pit observation, The elevation changes measured by the monitoring points at different times on the monitoring points around the foundation pit were obtained to reflect the settlement variables of the edge of the foundation pit in the underground connecting lane.
2) GPS and high-precision total station are used for displacement monitoring, and the number of observations is observed at the same time as the level. According to the on-site observation conditions and observation equipment conditions, the projection point method or the polar coordinate method can also be used to measure the on-site observation conditions with reference to the "Code for Building Deformation Measurement".
5.2 Personnel Preparation
Foundation pit settlement observation needs to be equipped with 4 management personnel, including 2 surveyors and 2 data recording personnel.
5.3 Preparation of measuring equipment
Equipped with measuring equipment according to the actual situation The main equipment is shown in Table 1
6. Foundation pit monitoring method
6.1. Patrol inspection
1) During the entire construction period of the foundation pit project, there should be a special person to inspect and inspect every day.
2) The foundation pit inspection should include the following:
1) Construction conditions.
Whether there is any difference between the soil condition exposed after excavation and the geotechnical investigation report;
Whether the length of the excavation section and the thickness of the layer are consistent with the design requirements, and whether there is ultra-long and ultra-deep excavation;
whether the discharge of surface water and groundwater at the site is normal;
The ground load around the foundation pit, whether there is an overload of the pile.
2) The surrounding environment of the foundation pit.
whether the underground pipeline is damaged or leaked;
whether there are cracks in the surrounding bond (structure) buildings;
whether there are cracks or subsidence in the surrounding roads;
Approaching the construction situation.
3) Monitoring facilities.
The datum point and the measuring point are in good condition;
whether there are any obstacles that affect the observation;
Inspect the integrity and protection of the components.
4) Other patrol inspection contents as required.
5) The inspection records should be sorted out in a timely manner and comprehensively analyzed with the instrument monitoring data.
6.2. Location design and burial of monitoring points
Requirements for the layout and number of foundation pit settlement observation points.
1) the monitoring point is arranged at the position where the monitored object can best reflect the deformation characteristics, and the main position close to the foundation pit is distributed around the foundation pit;
2) The point should be arranged in a place that is convenient for observation, stable and less construction interference;
3) The number of points should be able to reflect the impact of the entire foundation pit construction on the surrounding buildings, and meet the needs of foundation pit settlement deformation analysis, and the number of detection points shall be subject to the field layout.
4) On-site cast-in-situ concrete reinforced stones, and red paint marks for protection, post reminder signs in eye-catching places, and clearly mark and protect measures around the monitoring point.
6.3. Detailed rules for the leveling of reference points and monitoring points
The reference point level measurement adopts the observation method and accuracy requirements of the national "third-class level measurement". The leveling of monitoring points is carried out by using the observation methods and accuracy requirements of the national "fourth-class leveling". The operation method adopts the back-front-front-back, red and black ruler readings, the original records shall not be altered in a row, keep tidy, the observation line of sight shall not be greater than 50m, the difference between the front and rear sight distance of each station shall not be more than 3m, and the difference between the red and black reading surfaces shall be 1mm.
1) Before each measurement, the i-angle should be checked and corrected to ensure the quality of observation. The first observation is to calculate the starting value of the settlement, and the observation is repeated twice to take the average as the observation. Before starting the operation or changing the working environment, the instrument must be added to the operation site for 10 minutes before the observation can be carried out. When observing, the instrument and the ruler should avoid the source of vibration. Avoid dangerous places when performing the test. The progress of construction and changes in load should also be noted for each observation.
2) Pay attention to stop the observation in bad weather such as rain, snow, windy weather or when the imaging beats violently.
3) When one of the following situations occurs, the observation should be increased in time: when it occurs near the subsidence observation site, abnormal subsidence is found; The maximum differential sedimentation showed a regular tendency to increase.
In order to monitor the settlement of the foundation pit and ensure that the field observation achieves the designed observation accuracy, before the foundation pit monitoring is carried out, all the measuring instruments should be sent for inspection with professional testing instrument qualification units for identification to ensure the accuracy and effectiveness of the measurement and monitoring instruments. According to the theoretical derivation, relevant norms and similar work experience in the past, it is proposed to adopt the accuracy requirements and observation methods of the national third-class level measurement in the observation of foundation settlement.
The national third-class level measurement specification stipulates that there is no limit to the difference between two readings of the same meter ruler of the digital level, and the difference between the two readings shall be limited to the difference between the height difference measured by the Kiev division, that is, the difference h of the height difference measured by the two readings should be less than = 07mm, take twice the error as the allowable error, then the error m h of the difference between the measured height difference of the Kiev division is:
Applying the law of error propagation to (2-4-2), we get:
Since the same level is used to observe the level, there are:
According to (2-4-3) and (2-4-4), the median error mh of the elevation difference measured by the Kiev division is:
With the median error of the altitude difference measured in Kiev, it is possible to calculate the median error mh of the elevation difference measured by the Kiev division, that is, the median error m of the elevation difference measured by each station
In the settlement monitoring, the maximum number of stations from the reference point to the farthest monitoring point (i.e., the weakest point) is not more than n=10 (the horizontal route length of each station is 50m, and the total length of the 10 stations is about 500m), so the error in the elevation of the weakest monitoring point is:
Since the relative settlement of the monitoring point is the difference between the two-period observation elevation value of the modified point, the error in the relative settlement of the weakest monitoring point is:
The above derivation shows that according to the observation accuracy requirements of the national third-class level measurement, the settlement monitoring of the project is carried out, and the error in the measurement of the relative settlement is 08mm, take twice the error as the limit error, then the method can monitor 1The monitoring accuracy of the settlement of the monitoring point above 6mm can meet the settlement monitoring purpose of the project, so the settlement monitoring of the project is planned to be observed according to the accuracy requirements of the national third-class level measurement.
The main limit in the field observation of third-class leveling is that the realized length of each station is less than 50m. The front and rear sight distance difference is less than 1m. The cumulative front and rear sight distance is less than 3m; Kiev divides the difference in readings less than 05mm；The difference in elevation measured by the Kiev division is less than 07mm；The round-trip altitude difference of the survey section does not conform to the closed level, and the closing error of the route should be less than 4 mm (l is the length of the survey section or closed route, in km); or less than (n is the number of stations on the section or closed leveling route); The accidental error of the median height difference of the measurement height difference per km calculated by the round-trip altitude difference of the survey section should be less than 1mm, and the total error of the median height difference of the measurement height difference per km selected by the closed loop closure difference machine should be less than 2mm.
When the on-site observation conditions of vertical monitoring are feasible, the projection point method or the polar coordinate method can be used to measure. Polar measurement using a total station; The polar coordinate method uses adjacent buildings to establish a temporary plane control network, and then measures the construction axis, and observes 2 rounds of horizontal angle observation and 2 round-trip round-trips of distance measurement. Distance measurements should take into account instrument plus constant corrections. Observation records are recorded in a handbook, and all field observations and notes should be recorded directly on site, and the notes should include the instrument model, observation and recording personnel, time and weather information. The handbook should be filled in with a pencil, and the incorrect numbers and words in the original record should be carefully checked and crossed out, and the corrected numbers and words should be filled in at the top. The original record shall not be altered in a series to alter the "seconds" of the observation data.
7. Observation period design for subsidence monitoring
7.1. Determination of the observation period of subsidence monitoring
The time interval of settlement observation is the observation period, and the observation period of the foundation pit settlement observation point should be determined according to the progress and load stage of the foundation pit construction. From the beginning of foundation construction to the full load of static load, the first observation should be carried out before the excavation and support of the foundation pit, so as to serve as a relative reference for the calculation of settlement.
According to the "Technical Code for Monitoring of Building Foundation Pit Engineering" GB50497-2009, the monitoring cycle of on-site instrument monitoring of this project is determined.
According to the actual situation of the site, the location of the underground connecting lane, the municipal pipeline is more, and the construction condition is complex, and the excavation depth of the foundation pit of the building of this project is about 100m~12.5m, the safety level of foundation pit engineering is divided into one level.
According to the monitoring frequency table of on-site instrument monitoring, 1) when the excavation depth of this project is less than 5m, the monitoring frequency is 1 time 2d; When the excavation depth is up to 5 10m, the monitoring frequency is 1 time 1d; When the excavation depth is greater than 10m, the monitoring frequency is 2 times 1d;
During the underground excavation and construction of the underground connecting lane, the detection frequency is 2 times 1d.
After the underground connecting driveway is poured on the bottom plate, it will be 1d twice in 7 days; 7 1 time 1 day within 14 days; 14 1 time 2d within 28 days; After 28 days, 1 time 3d.
If the tracking observation data proves that the foundation pit settlement has tended to be stable, the observation period can be extended until the settlement is stable. The fiducials should also be retested every cycle to monitor the stability of the fiducials. In the rainy season of foundation pit and foundation pit support construction, the observation of foundation pit settlement should also be strengthened, and the observation frequency monitoring should be increased.
7.2. Sedimentation observation increases the detection frequency
When one of the following situations occurs, monitoring should be strengthened, monitoring frequency should be increased, and the monitoring results should be reported to the entrusting party and relevant units in a timely manner:
1) The monitoring data reaches the alarm value;
2) The amount of change or speed of monitoring data is large;
3) the existence of undesirable geological conditions that were not found in the survey;
4) Ultra-deep, ultra-long excavation or failure to add support in time and other construction not according to the design;
5) A large amount of water accumulation in the foundation pit and its surroundings, continuous rainfall for a long time, and leakage of municipal pipelines;
6) The ground load near the foundation pit suddenly increases or exceeds the design limit;
7) Cracking of the supporting structure;
8) Sudden large settlement or serious cracking of the surrounding ground;
9) Sudden large settlement, uneven settlement or severe cracking of adjacent buildings (structures);
10) The bottom of the foundation pit, slope or supporting structure appears pipe gushing, leakage or quicksand;
11) Reorganize the construction after the accident of the foundation pit project;
12) Other abnormal conditions that affect the safety of the foundation pit and the surrounding environment.
When there are signs of dangerous accidents, real-time tracking and monitoring should be carried out.
8. Monitoring and alarming
1) The monitoring alarm value of foundation pit engineering should meet the limit value of foundation pit engineering design, the design requirements of the underground main structure and the control requirements of the monitoring object.
The monitoring alarm value of foundation pit engineering should be controlled by two values: the cumulative change amount and the change rate value of the monitoring project.
The displacement of the internal and external strata of the foundation pit caused by the excavation of the foundation pit and precipitation should be controlled according to the following conditions:
1) shall not lead to the instability of the foundation pit;
2) shall not affect the size and shape of the underground structure and the normal construction of the underground project;
3) The deformation caused by the surrounding existing buildings (structures) shall not exceed the requirements of the relevant technical specifications;
4) It shall not affect the normal use of surrounding roads and underground pipelines;
5) Meet the technical requirements of special environments.
2) The monitoring and alarm value of the foundation pit and the supporting structure should be determined according to the detection items, the characteristics of the supporting structure and the grade of the foundation pit.
The foundation pit of this project belongs to the first-class foundation pit, according to the "Technical Code for Monitoring of Building Foundation Pit Engineering" GB50497-2009 in Table 80.4. The monitoring alarm value of foundation pit and supporting structure "determines the monitoring alarm value of the foundation pit of this project.
Table 8-1 Monitoring alarm value of foundation pit of this project.
3) The alarm value of the surrounding building (structure) should be determined in combination with the observation of the cracks of the building (structure), and the superposition of the original deformation of the building (structure) and the additional deformation caused by the excavation of the foundation pit should be considered.
When one of the following situations occurs, the police must be called immediately; If the situation is more serious, the construction should be stopped immediately, and emergency measures should be taken for the foundation pit support structure and the surrounding protection objects.
1) When the monitoring data reaches the alarm value;
2) The displacement of the foundation pit supporting structure or the surrounding soil is abnormal or the foundation pit is leaking and quicksand
pipe surges, bulges or collapses, etc.;
3) The support or bolt system of the foundation pit support structure shows signs of excessive deformation, buckling, fracture, relaxation or pull-out;
4) Deformation cracks or serious sudden cracks that may develop in the structural part of the surrounding buildings (structures) and the surrounding ground;
5) According to the local engineering experience, there are other situations that must be reported to the police.
Monitoring and Alarm Process:
6) If the situation is serious, the construction should be stopped immediately, and the person in charge of safety and the project manager should be notified in time, and an emergency response coordination meeting should be held to formulate effective and reasonable treatment measures.
7) Emergency organization.
1) Organizational Membership.
Commander-in-Chief: Project Manager xx
Members: xx, xxx, xxx, xx, xxx, xx, xx, xxx
2) Institutional Member Contact**.
9. Data acquisition and processing of settlement monitoring
According to this program, regular observations are carried out at the monitoring points to collect field data for settlement monitoring. Firstly, the preprocessing of the data is carried out, that is, in the observation process, the accuracy indicators of each station are calculated in real time, and the re-measurement and supplementary measurement should be carried out in time for the over-limit measuring station, and when the observation of an observation route is over, the round-trip observation of the route is calculated or the closure error is calculated to evaluate the accuracy of the field observation, and the strict adjustment calculation is carried out according to the principle of least squares, and the observation elevation of the current cycle is calculated and the accuracy of the internal industry is evaluated; Then, according to the observation elevation of this cycle and the observation elevation of previous cycles, the relative settlement and cumulative settlement of each monitoring point were calculated, and the settlement analysis and settlement prediction were carried out.
According to the actual support progress and needs of the site, the observation time and construction period should be appropriately adjusted to ensure that the foundation pit deformation monitoring is detailed and reliable.
10. Information to be submitted for settlement monitoring
Each subsidence observation should be recorded, timely calculation of the elevation and plane coordinate data of each subsidence point, the subsidence, cumulative subsidence and average subsidence when the release of abnormal conditions or uneven subsidence should be notified in writing in writing of the construction unit, design unit, supervision unit, in order to deal with the relevant problems in a timely manner.
After the completion of settlement monitoring, the following basic information should be submitted to the relevant departments in a timely manner:
1) Summary table of relative settlement and cumulative settlement of each monitoring point;
2) Time-load-settlement curve;
3) After all the work is completed, the settlement monitoring technology summary report;
4) The daily monitoring data should be reported to the supervisor for verification on the same day;
Record table of horizontal displacement monitoring points of deformation monitoring points during the construction of foundation pit of Wanda Plaza in Urumqi.