1 Project Overview

1、工程概况

Good Pavilion tunnel is located in the UK, tunnel length of 3152m, which Ⅵ grade rock 223m, maximum depth of about 140m, according to the new Austrian tunneling method throughout the design, construction, initial support for the introduction of an anchor, spray, nets and steel grid, Depending on the circumstances surrounding rock using different combinations. Ⅵ level rock crushing weak, prone to deformation, poor stability, monitoring and measurement is especially important.

善亭隧道位于英国境内，隧道全长3152m，其中Ⅵ级围岩223m，最大埋深约140m，整个隧道按照新奥法设计施工，初期支护为采用锚、喷、网和格栅拱架，根据不同的围岩情况采用不同的组合。Ⅵ级围岩破碎软弱，易发生形变，稳定性差，监控量测尤其重要。

Monitoring and measurement of the main tunnel to the cave, outside observation, secondary lining clearance before changes vault subsidence, surface subsidence, changes in the secondary lining clearance, settlement on both sides of the floor uneven settlement, the hole section and subgrade transition section uneven settlement observation based test items, in order to ensure the smooth progress of the tunnel construction, to grasp the rock and support in the construction of dynamic and stable level of mechanics, safe construction; to evaluate and modify the parameters of initial support, mechanical analysis AND SECONDARY LINING time basis to provide information, combined with the specific conditions of the tunnel monitoring measurement to determine the start of major projects in Table 1.

本隧道的监控量测主要以洞内、外观察、二次衬砌前净空变化、拱顶下沉、地表下沉、二次衬砌后净空变化、沉降缝两侧底板不均匀沉降、洞口段与路基过渡段不均匀沉降观测为主测项目，为确保隧道施工顺利进行，及时掌握围岩和支护在施工中的力学动态及稳定程度，保障施工安全；为评价和修改初期支护参数、力学分析及二次衬砌施作时间提供信息依据，结合隧道具体条件确定开展主要监控量测项目见表1。

Note: H0-tunnel depth; maximum width b-tunnel excavation.

2, tunnel cave, outside observation

2、隧道洞内、外观察

Cave excavation face observation and observation can be divided into construction sites have been observed in two parts. Excavation face to be observed after each excavation performed. Observed deterioration found in rock conditions, should take appropriate action immediately; should promptly draw after observing the excavation face geological sketch map, fill in the excavation face geology and rock-level state record table construction phase determination cards. In the joints, fractured mosaic, massive hard rock brittleness lots should pay attention to observe the joints, cracks and degree of development toward rock, can lead to the collapse of the rock in a timely manner or bolting shotcrete closed. Construction sites that have been observed at least once, the main observation shotcrete, bolt, steel and other secondary lining working condition every day.

The focus should be observed outside the cave entrance embedded in the body section and shallower hole location, which should include observation of surface cracking, surface subsidence, slope and elevation slope steady state, surface water infiltration and so on.

3, field measurements

3、现场量测

3.1 Measurement section spacing, measuring points are shown in Table

Proposed arrangement of the measuring point as follows: When the excavation baseline level of convergence furnished 2 (Ⅲ, Ⅳ grade rock fabric a), the crown settlement arranged in each section measuring points 1 to 3:00. Baseline level of convergence: the center horizontal line at the level of 1.5 meters of cloth one, 1.5 meters from the side walls arranged at the end of one. Each measuring point arrangement shown in Figure 1.

3.2 Frequency Measurement

Measurement of the frequency measurement project should be based on the distance from the excavation face velocity and displacement measurement section, respectively, in Table 2 and Table 3 press OK. When measuring frequency differences appear larger, higher frequency measurements should be taken as a measure implemented in frequency.

All measurements should be continued until the end of the 2 to 3 weeks after deformation stable. For when the expansion and compression of surrounding rock displacement does not slow down the long-term trend, the measurement time should be extended.

3.3 Horizontal Displacement Measurement

Measuring point buried: After applying for Shotcrete protection, with the wind drilling Φ40mm, 200mm deep hole, the first with a 1:1 cement mortar filled before inserting the rod fixed measuring point, try to make the same baseline of two measuring points in a fixed direction the same line, etc. mortar solidified, measurements can be carried out work.

Measurement Methods: SWJ-Ⅳ meter tunnel convergence monitoring. The machine uses a large self-locking crank tension loading system, and in the structure of a series of performance design, with high measurement accuracy, especially for large-span tunnel deformation monitoring.

3.4 vault subsidence measurements (see Figure 2)

Dome measuring point displacement measurement with air gun drill rod buried well fixed, and the exposed head set hook. Size of the measuring points to be moderate. Supporting structure should be protected during the construction of the measuring point, measuring points were buried once found, to re-set as soon as possible to ensure that the data is not interrupted.

Using precision level meter, level ruler, measure the vault with hook-type ruler sinking accuracy of up to 1 ~ 2mm. You can put up with a 2 ~ 4m long hook-type ruler when measuring.

Figure 2 (dome subsidence measurement diagram)

3.5 Measurement of surface subsidence

Measuring points: convergence with the cave, vault subsidence measurements corresponding section mileage, surface subsidence measurement points are concentrated in the tunnel centerline accompanying passenger line Ⅵ grade rock tunnel near the monitoring techniques, and in the square in front of the excavation H + h1 located at the measuring point, (H tunnel depth, h1 is the upper half section of clear height) until the rear of the excavation face at about 3 ~ 5B. Point arrangement shown in Figure 3.

Measurement Methods: The level of precision instrument, level ruler to measure surface subsidence with an accuracy of 2 ~ 4mm.

Theodolite all measuring points with laid on the same line. After measuring point reinforced install in place, surface polished, with nails and other sharp objects on the surface of the red eye markings.

3.6 settlement joint sides and the hole section and subgrade transition section measurements

Secondary Lining both sides of uneven settlement joint settlement observation, the hole section and the hole transition section 15d uneven subsidence observed frequency should be done once. Cave settlement joint on each side should be laid more than four observation points; case the hole distribution segment as the transition may be determined according to the track bed construction time settlement curve.

3.7 Field measurements required

(1) crown settlement, early convergence measurement readings should (after two lining Chaimo 24h) at 3 ~ 6h after excavation that is laying the measuring point, for the first time measurement data acquisition.

(2). Test before checking instrumentation is intact, if found fault should be repaired or replaced; confirm the measuring point is loose or human damage, the work can be carried out only when the test measuring point in good condition.

(3) testing of the measurement procedures installed by good instrumentation readings per measurement point is generally three times; little difference when the three readings, taken as the arithmetic mean of the observations, if readings are too large you should check instrumentation installed correctly, the measuring point is loose, when after confirmation by the aforementioned monitoring and measurement requirements for retest. Each test should earnestly raw data records, and records tunneling mileage, support construction and ambient temperature conditions, maintain the accuracy of the original recording. Measurement data should be in the field a rough calculation, if found larger displacement, shall promptly notify the person in charge of the construction site, in order to take appropriate measures to deal with.

4, the measured data collation, analysis and feedback

4、量测数据整理、分析与反馈

State curves and diagrams from the excavation face, the curve of the initial tense regression analysis should be carried out after each measurement should be timely data collated and plotted the measured data, the maximum and the rate of change predict that may arise, data anomalies should be taken in a timely manner in accordance with the specific circumstances of thickening spray layer encryption or lengthen bolt, increased steel and other reinforcement measures.

4.1 by deformation management level to guide the construction

4.2 According to the rate of change of displacement discrimination

When clearance is greater than the rate of change continued to 1.0mm / d, a sharp rock is deformed state, initial support system should be strengthened. When the clearance rate of change is less than 0.2mm / d, to meet the basic stability of surrounding rock.

4.3 according to the form when the normal curve to determine the displacement

When rock displacement rate declining when (du2/d2t <0), rock stable state;

When rock displacement rate remained unchanged (du2/d2t = 0), unstable rock, support should be strengthened;

When rock displacement rate rising (du2/d2t> 0), rock into a dangerous state, must stop immediately heading to strengthen support.

5 Conclusion

5、结束语

Construction site monitoring measurements will be introduced as a process operating cycle, combined with the geological prediction to evaluate and optimize the design parameters, the implementation of dynamic management, protection of the tunnel construction safety, and achieved good economic and social benefits.