Methods for Measuring Convergence and Crown (2) Convergence meter Settlement on Rocks ( JCJS 371 1-2001 ) Convergence meter should bc able to read the distance between 2 points where measurement pins are set with the accuracy of O.i - 0.0lmm by the steel tape with l. General Rules fixed tensile force and vemier or dial gauge. l.1 Purpose of Measurement The purpose of this measurement is to measure the displacement of wall in tunnels and underground caverns. (3) Thermometer Thennometer should be able to rneasure temperature with satisfied acouracy so as to revise measurement 12 Application R,ange An object for this measurement is for tunnels and underground caverns excavated in rock results. 2.2 Crown Settlement Measurement with Level Measurement pin, reference point and measuring 1.3 Definition ofthe Terms (1) Convergence is relative displacement between walls in tunnels and underground cavems. (2) Crown settlement is vertical direction displacement at the crown in tumels and underground caverns. Crown is, herein, defined as the highest point in tunnels and instruments are used for crown settlement measurement. (1) Measurement pin Measurement pins should be fixed to crown to measure crown settlement and its structure must be attached to measuring instruments. Measurement pin must be the configuration which can be fixed definitely on rock at underground caverns. (3) Tunnel is an underground structure constructed in the planned site having a prescribed section size and the cross section area must be more than 2m2 without affecting excavating method. (4) Underground cavern is an underground structure excavated in rock like underground power station, underground station, underground storing facility, and crown to measure crown settlement accurately. (2) Reference point Reference point should be the standard of crown settlement measurement. (3) Measuring instrument Measuring" instrument consists of level and tape. It should be able to read with the accuracy up to I mm. 2.3 Measuring Convergence and Crown Settlement by Total so on. Station Measurement point, reference point and total station are lncidental articles] i . The content should be reported if a method which is partly. used for each measurement by total station (1) Measurement point different from this standard is used. Measurement point is the target which is set to measure 1 .2 Application Range This standard may be also applied to tunnel and underground convergence and crown settlement. Measurement point should have the structure that can be definitely fixed cavem excavated in soil ground. on rock in order to measure convergence and crown settlement accurately. 2. Measuring Instrument Following instruments should be used as measuring tools. (2) Reference point Reference point should be the standard of convergence 2.1 Convergence Measurement with Convergence Meter Measurement pins, convergence meter and thermometer are used for convergence measurement. and crown settlement measurement. (3) Total Station Total station is the one in which processes the (1) Measurement pin Measurement pins should be fixed to walls to measure convergence and its structure must be attached to convergence meter. Measurement pin must be the configuration which can be fixed definitely on rock to measure displacement bctween walls accurately. - 355 - measuring result of electronic goniometer and macrometerby microprocessor. Total station whose mlnimum distance display is under O.1 mm and angle display is under I " should be used. [Incidental Articles] Ins*taliation Part 2 l (1) Figure-1 shows the example of a measurement pin. A measurement pin consists of installation part of measuring Steel 'I'ape instrument and fixation part in rock Fixation part in rook should have long enough to fix defmitely in rock. Figure-3. Example of tape for crown settlement Fixation part in rock (Deformed Bar, etc.) Installation part of measuring instrument measurement Target Pixation part in rock (Deformed Bar, etc. ) Figure-1 . Example of a measurementpin (2) Figure-2 shows the example of a convergence meter. The Figure-4. Example of a measurement point accuracy of reading gauge should be selected as the expected convergence amount. (2) Structure of reference point should bc the same as the one of measurement point. Insta]lation Part e Dia] Gauge of Vernier e 3 3. Measuring Method Measuring of convergence and crown settlement should Insta]lation Part Steel lr'ape -¥ rind Up Handle be executed as following procedure. 3_1 Measuring Line Arrangement / Measuring Point Measuring line arrangement for convergence measurement should have more than three lines that are horizontal and Figure-2. Example of a convergence meter diagonal as general. Measuring point for crown settlement measurement should (3) Convergence meter is strongly influenced by the temperature. Therefore, measuring accurate temperature be the highest point of underground cavem 32 Initial Value Measurement Measuring the initial value in earlier time after excavation and correcting the measuring value from convergence meter are needed. is desirable. Measurement should be executed before starting next excavation at the latest as general. 3_3 Measurement Frequency 2.2 (1) one of convergence meter. (See Figure- I .) (2) Nail and so on is usually used for reference point- (3) Figure-3 shows the example of tape used for measuring. displacement speed. Measurement should be executed until displacement speed becomes small enough. 3.4 Measurement using Convergence Meter 2.3 (1) Frequency of the measurement should be set as Structure of measurement. pin should be the same as the (1) Setting up measurement pin Figure-4 shows the example of a measurement point. Measurement pins should be fixed on rock. Measurement point consists of reflection target and (2) Measurement fixation part in rock. Fixation part in rock should have Measurement should be executed to fix both ends of long enough to fix definitely in rock. 356 * (2) Figure-7 shows the outline of measurement by a. Figure-9 shows the outline of measurement by total station. b. Measuring accuracy is greatly influenced by stain in convergence meter. reflection target so that the surface should be cleaned if necessary. cranlp fi);ing steel ape Reading the ¥ atue b) c. Measuring accuracy is greatly influenced by installation dia: gauge or ¥"ernier ¥, 'leasurernent pjn Instailaticul part Jl_ J ,i r position of total station so that the content should be ¥' ieasurement pin Insta] Iation part e:3 e recorded and reported. d. Measuring accuracy is greatly influenced by the Stee! tape environment where is measured so that it is desirable to measure at the environment such as less dust as possible. Fixation of instal]ation part to measureme t pjn Fixation of installation part to ! 1easurement pjn Figure-7 Outline of measurement by convergence meter 35 Meilst rillX l'()illt View (1) Reference point should be checked for its height if I{efercnce / necessary. (2) The content should be recorded and reported when measurement pin is set besides the rock such as support. 1',)t; l Stati()n (3) Figure-8 shows the outline of crown settlement ,view l. l efe ence measurement by level. X I eference l)oi: t 1easurement pin l efere]1ce l'oint y Figure-9 Outline ofmeasurement by total station Reference b} ¥,iel 4* Organization ofthe Result Tape Reference b¥ 1'iel¥" Tape The relationship between its progress time and progress of Reference point excavation should be organized for the result of convergenoe (nail) and crown settlement. l,eveJ [IncidentalArticles] Progress of excavation means special mention of changing Figure-8 Outline of crown settlement measurement by level support and construction method, which is the change of face position and the lowering of roadbed. Besides progress of 3,6 (1) Reference point should be checked for its coordinates if excavation, the factor should be recorded and reported when the displacement speed had made a big change because of necessary. (2) The content should be recorded and reported when measurement pin is set besides the rock such as support. Measurement point should be set up according to the setting up of measurement pin. (3) 357 earthquake, downpour, and adjacent construction. convergence meter into the measuring pin; and measure tlncidental Articlesl the length between measuring line by using steel tape 3.1 Measuring point and measuring line arrangement for and vemier or dial gauge with fixed tensile force. Value convergence and crown settlement is desirable to decide should be read up to the minimum readable value. by the condition of ground and accumulaied measurement Convergence is calculated by the difference between data. For a large-scale measurement in underground caverr initial value and measuring value. it is desirable to decide properly by the cavem scale and To measure the temperature while measuring shape. Figure-5 is the example of measuring point and convergence is needed. measuring line arrangement. 3.5 Measuring Crown Settlement by Level 3.2 The relationship between the time when initial value is measured and construction cycle, and time from the (i) Setting up reference point Reference point for measuring crown settlement by completion of face excavation at measuring section should ievel should be set up in the place where displacement be recorded and reported. does not occur for a long time. 3*3 a. Measurement frequency should be decided considering (2) Setting up measurement pin ground condition, management criterion additional to Measurernent pin should be certainly fixed on rock. (3) Measurement displacement speed. b. Completion ofmeasuring is about one week after the amount Measurement should be executed to at.tach tape to of displacement converges to the definite value. measurement pin and read the height of measurement pin by the unit of I mm. ./// ¥ '¥ . Measure:nent should be also executed to attach tape to l/)' ¥'¥¥.¥ .1/,! ¥ ¥ ･¥ reference point and read the height of reference point 7-f .¥ ¥. " / ' ______¥･ - /' / -L/" by the unit of Inun. ¥: / Crown settlement is calculated by the difference of ./' ¥ t¥ ¥. vertical interval between reference point and ¥ measurement pin. 3.6 Measuring Convergence and Crown Settlement by Total Station (1) Setting up reference point Reference point for measuring convergence and crown settlement by total station should be set up in the place Example of Tunnel Exampie of Un erg ovnd Caven Figure-5 Example of measuring line arrangement and measuring point where displacement does not occur for a long time. (2) Setting up measuring point Measuring point should be certainly fixed on rock. 3.4 (1) Figure-6 shows the example of setting up of measurement (3) Measurement pin. The content should be recorded and reported when Total station should be set up in the place where is not measurement pin is set. besides the rock such as support. influenced by the vibration of construction, and the coordinates of each measuring point and reference Instaliation part of measuriTlg nstrur]]ent i point should bs read. The distance ofmeasuring line is obtained by the coordinates of each measuring point, and then convergence is calculated by the difference between the initial value and measuring value. Furthermore, crown sett.lement is calculated by the difference of vertical interval between the reference point and measurement pin. F igure- 6 358 - Example of setting up of measurement pin 5. ReportingArticles The following articles should be reported. (1) The contents when the partially different method has been used from this referenc (1'_) Geological condition at measurin*' section (3) Setting up condition of support (4) Starting date and time of measurement (5) Measuring line arrangement / Measuring point (6) Used measuring machinery and instruments (7) Description and setting up method of measurement pin and measurement point (8) Reference point and its position when it has been used (9) Changing date and time and new position of reference point when it has been changed (lO) Result of convergence and crown settlement, and relationship among the results, progress time and progress of excavation ( I I ) Any other articles which should be specially mentioned [Incidental Articles] 5 . Setting up condition of support means description, thickness and strength of shotcrete; description, Iength and pattern of rock bolt; description and setting interval of steel support; and construction condition such as PS anchor. 359