发布时间：2011-7-14 19:43:00|| 点击：3839次|| 文章分类：翻译案例|| 发布人：翻译家(Fanyijia.com)
The works of this section include excavating of tunnel body, carriage gallery, pedestrian gallery, auxiliary gallery and the related works such as shaft construction, drilling and blasting, tunnel supporting, excavated material loading and hauling etc..
II. GENERAL REQUIREMENTS
1. The Contractor shall submit construction program (including excavation sequences, explosion, construction lighting, ventilation, drainage, support, ballast removal, lining, etc.) that is most suitable to the actual conditions of the tunnel, according to such conditions as geology, mechanical equipment to the Engineer for review and approval 28 days before excavation. The New Austrian Tunneling Method is advisable to be applied. Timely change may be also made for the construction method based on the actual conditions and must be approved by the Engineer to match with changes of specific conditions.
2. The Contractor shall adopt modernization construction technique and reasonably arrange procedures, organize scientifically construction according to the approved construction program to ensure qualified project quality and reasonable schedule.
3. The Contractor shall arrange correctly measurements during construction to ensure that the tunnel is constructed according to design direction and slope gradient and excavated section conforms to dimensions shown on the Drawing. Excavated dimensions are done correctly. Benchmark is located at each 50m inside tunnel.
4. The Contractor shall not be relieved of his responsibility in defects or failure of tunnel works due to the construction method approved by the Engineer.
5. During construction, according to the direct observation to cutting face, the mseasurement to deformation of the surrounding rock, with assistant of advanced geological prediction and supplement of strata formation, lithological characters and groundwater, the Contractor shall raise his modification opinion for classification of surrounding rock, judge stability of the surrounding rock around the gallery, put forward corresponding treatment and submit to the Engineer for approval.
III. EXCAVATION OPERATION
1. Excavation Requirements
(1) The Contractor shall, in accordance with the approved construction methods or the succeeding approved modification plans, complete the excavation operation. Before the completion of the protection work of side slope at the tunnel opening, the tunnel body excavation shall not be started.
(2) The Contractor shall adopt the excavation method that reduces disturbance on the surrounding rock in tunnel body in order to utilize the self-supporting characteristics of the surrounding rock to the maximum limitation. For methods of excavation of different surrounding rock, stipulations in Technical Specifications for Construction of Highway Tunnel (JTJ 042-94) shall be referred to.
(3) During excavation of tunnel body, all cross section dimensions shall conform to the requirements on the Drawings. Side ditch, cable trench and foundation of sidewall shall be excavated simultaneously. All the excavation shall be carried out according to the excavation line shown on the Drawings, and shall be completed in one excavation. In the course of excavation, the Contractor shall from time to time survey the position of tunnel axis and elevation. Before construction of tunnels chambers for provision, they shall be checked against the Drawings to ensure the quantity and accurate position of them.
(4) During excavation, the Contractor shall use methods, which are beneficial to the reduction of over-excavation and the stability of the surrounding rock. The cost of all materials and construction for the overreach beyond the allowed range made by the Contractor for whatever cause including backfill of over-excavation are the Contractor's liability.
(5) Under-excavation shall not occur in excavation of tunnel except when rock stratum is perfect with compressive strength more than 30MPa, and the Engineer confirms that the under-excavation will not affect the structural stability and strength of the linings, in this case, individual part of a rock (not greater than 0.1 m2 per square meter) may intrude into the lining within 50mm. Under-excavation on the cross section less than l m above footings of the arch and the wall is strictly forbidden.
(6) When using bench cut method in tunnel construction, the bench is preferable not to be divided into too many steps, the distance of lower part and the upper part of the bench shall satisfy as far as possible the normal operation requirements of the machines/tools and the re-handling of ballast shall be reduced to the minimum. provided the top surrounding rocks are broken and following up support is required, the bench may be properly lengthened.
(7) When the working faces of opposite sides are nearly excavated through, the construction of both sides shall contact with each other tightly. When the distance of two working faces remains 15m, the tunnel shall be excavated through from one side.
(8) In excavation of shallow buried tunnel, it should be carry out to decrease the footage to prevent collapse, which shall benefit to diminish the settlement of ground surface. So, according to actual conditions, the proper measures are taken as follow:
a. Single arm tunneling machine or pneumatic pick is used so as to decrease the disturbance of surrounding rock in construction. The principle of short footage, strong support, weak blasting, regular observation and surveying shall be observed for blasting excavation;
b. Strengthen the treatment of springing, and set anchor bar of springing;
c. Construct inverted arch or temporary inverted arch in time;
d. Make deep hole rock grouting for the surrounding rock 2~3m around the periphery of tunnel when deformation of the primary support is too large and reinforcement is not appropriate..
e. When constructing in weak and broken surrounding rock of Class Ⅳor ClassⅤ, or there is water emerging in the tunnel, such measures shall be adopted as pre-grouting, or setting stratum anchor bar from the ground surface, or ring consolidation grouting in the tunnel or strengthening the stratum by using pipe-shed.
f. Observation and feedback of settlement of ground surface and settlement of arch crown shall be strengthened so as to instruct construction.
(9) Ultimate deviation of two constructional centerlines in opposite directions on the through face of tunnel shall conform to stipulations in Table-1. The additional works caused by through error shall not be measured and paid separately.
Table -l Ultimate Through Error of Tunnel Centerline
(10) When the bench mark of tunnel portal is located outside tunnel, measurement deviation and root mean square deviation on the through face caused by laying out route shall conform to stipulations in Table-2.
Table-2 Root Mean Square Error on the Through Face
(11) For soft and weak broken rock at tunnel opening section, usual measures are taken to stabilize excavated work face as follows: provided core part during circular excavation; excavation operation surface sealed by shotcrete; advance anchor bolt or advance tubule; pipe-shed; Advance tubule grouting; temporarily inverted arch subseal, pre-caste grouting of excavation operation surface and surrounding rock etc. Construction is carried out according to requirements of Drawing, if unspecified, the measures shall be selected according to geologic condition, ground water state and construction method during construction, this should be submitted to the Engineer for approval.
(12) When soft and weak surrounding rock at tunnel opening is excavated using bench cut method in tunnel construction, the distance of lower part and the upper part of the bench shall be less than 30m; when tunnel opening section is located in the bulk congeries, excavation is done using micro-benching tunneling method and circular cut provided core part soil method, the distance of lower part and the upper part of the bench shall be less than 5m; inverted arch and arch steel frame shall sealed timely, inverted arch concrete shall be grouted in time to avoid excessive settlement and intruding into design limited range.
2. Blasting Design
(1) In the blasting excavation in rock tunnel, key factors of blast technology, such as the size and depth of drill-hole, the interval between holes, the quantity of dynamite, the distribution of drill-hole, and the sequence of blasting, shall be studies carefully and strictly controlled.
At least 14 days prior to blasting construction operation, the Contractor shall complete the design of drilling and blasting, and submit it to the Engineer for approval.
(2) The design shall be carried out based on the comprehensive study of geological conditions, excavated section, method of excavation, excavation cycle footage, machines/tools of drilling, blasting materials, etc. The main contents are: layout of blast holes (including hole cutting type, drilling depth and obliquity); structural diagram of dynamite filling (including amount of dynamite and blast hole stemming method); parameter table of drilling and blasting; blasting method and sequence, blasting diagram (shall be drawn if necessary), and main technical and economic indices and necessary descriptions.
(3) Smooth blasting or pre-splitting blasting shall be used in drilling and blasting design. Blasting parameters shall be selected and determined through tests. If test conditions are not available, relevant parameter in Technical Specifications for Construction of Highway Tunnel (JTJ 042-94) may be referred.
a. Technical requirements for smooth blasting:
(a) Residual traces of blast holes shall be evenly distributed on the excavation contour surface. Retaining rate of blast hole trace: not less than 80% for hard rock, not less than 70% for median hard rock, not less than 50% for soft rock.
(b) Rock surface between two neighboring holes shall be flat and even, no evident blast fissures are allowed on the hole wall.
(c) Bench type deviation that appears between two neighboring holes shall not be greater than 150mm.
(d) The biased error of borehole shall not exceed 1°.
b. Requirements to the pre-splitting blast
(a) Prior to igniting the main blast hole, instantaneous blast in single-row and close rim hole may be used to obtain the pre-splitting Surface along excavation contour line which shall reduce the damage of outer layer of rock resulting from the main blast hole.
(b) The most ideal condition is that a single break line shall connect nearby blast hole one by one, and half blasting trace of the rim hole section is maintained in surrounding rock after blasting.
(c) The pre-splitting seam width of the pre-splitting blast hole is advisable to be not less than 5mm in general.
(d) The biased error of borehole shall not exceed 1°.
3. Drilling and Blasting Operation
(1) Drilling and blast operation shall be carried out according to its design. When the excavation condition changes, corresponding changes of blasting technology shall be made according to the variation of the condition of surrounding rock.
(2) Prior to drilling holes, the centerline and the level of excavated section, the outline of the section shall be drawn and the location of blast holes shall be marked in accordance with the blast design. When it conforms to the design requirements through checking, the drilling of holes may be started.
(3) Depth, angle and interval of blast holes shall be determined in accordance with design requirements and shall confirm to the requirements of design accuracy.
(4) When all holes have been drilled, check shall be carried out in accordance with the arrangement drawing of the blast holes, and records shall be taken. When qualification is proved through inspection, dynamite filling may be started.
(5) Mud, accumulated water, and rock powder in blast holes shall be blown out and washed clearly prior to filling the dynamite. All blast holes shall be blocked up timely with stemming. The blocked length of rim holes shall not be less than 200mm.
When the pre-splitting blast method is used, blocking up shall be made from the top of dynamite package but not from the mouth of the holes only.
(6) When electricity is adopted for ignition, the operation shall be carried out according to stipulations in Construction and Acceptance Specification for Earthwork and Blast Work (GBJ201-1983) and Technical Specifications for Construction of Highway Tunnel (JTJ 042-94).
(7) Rim holes are available to be detonated at the same time. They may be detonated in groups according to the geological condition, and blast shocking has to be controlled when operated in soft rock section. Or the rim holes are densified to detonated in small diameter hole and less explosive.
(8) After blasting, exclusive person shall be assigned to clear the top and the surrounding, meanwhile inspecting the working face and un-lining section shall be carried out. If it is discovered that danger may occur, the Contractor shall take measures in time for eliminating.
(9) The excavation and blasting for continuous arch tunnel shall carry strictly out the principle of Short Footage, Weak Blasting and operation requirements of Blasting and Vibration. Excavation and blasting of nucleus rock in work face shouldn’t affect and even damage construction safety of lined structures.
4. Operation in Thundering and Lightning Period
(1) When thunder and lightning are approaching, all the ground or underground transport of dynamites and short distance hauling shall be suspended immediately; all personnel shall be evacuated to the safe places. The working personnel inside the tunnel shall be informed of the coming and passing over of the thunder and lighting by signals.
(2) In sections where the blast work has been finished, the Contractor shall provide, install and use approved thunder and lightning monitor apparatus and automatic alarm devices.
5. Blasting and Vibration
(l) The ground vibration caused by blasting or other operations are not allowed to damage existing building and public facilities.
(2) The Contractor shall provide qualified instruments, and assign measuring personnel and document analysis personnel, monitor and record every vibration situation of blasting and situation of air-pressure boost, adjust the blasting operation to make the vibration not exceed allowable value to prevent excavation instability.
(3) All blasting and construction operations shall guarantee the maximum velocity of vibration to existing building not exceed 25mm/s.
For new cast concrete, the vibration velocity allowed shall not exceed the stipulated values in Table-3:
Table-3 The Vibration Velocity Limited Value of New Cast Concrete
(4) The blast shock associated noise measured in the existing building near the blast point shall not exceed 130dB. In recording the situation of blast with maximum shock recorder by wire frequency reaction, the extra-pressure of air must not exceed 0.005Mpa. All the instruments and equipment related to the monitoring shall be provided by the Contractor and used according to the relevant requirements.
(5) Blasting is be strictly forbidden in the non-blasting area regulated in the Contract Drawings. The related data of vibration record shall be submitted at any Time to the Enginneer for inspection, and duplicated copy shall be provided when necessary.
6. Safety Measures of Blasting
(l) Various works like managing, processing, transporting, inspecting and destroying of blasting materials, shall conform to relevant stipulations in Safety Regulations for Blasting (GB6722-2003).
(2) The original records for receiving and using of blasting materials shall be well done and well filed.
(3) During blasting, all personnel shall withdraw to areas outside the effective range, where normally shall be far away for the blasting site with a distance not less than 200m. In period of blasting, besides electric circuits for ignition, all other power or light circuits shall be switched off or move to places not less than 50m away from the blasting point.
(4) If the excavation work and lining work are to be taking place in parallel, a distance, which is usually not less than 30m, shall be kept according to the strength of concrete, surrounding rock character and the scale of blasting.
(5) In gas tunnel, electric firing, permissible explosive and millisecond detonator must be adopted, while fuse and exposed cartridge are prohibited.
(6) Before charging and blasting in gas tunnel, safety inspection must be done to ensure the gas density less than 1%.
(7) After blasting, the Constructors shall not allowed personnel to enter the blasting area until the smoke is blown over by fresh air, air in the work face is checked to be qualified and all personnel shall wait more than15min.
7. Safety Measures for Harmful Gas
(l) If harmful gas is existed in the tunnel, all the personnel shall stop work immediately and withdraw to the outside of tunnel. The Contractor shall take treatment measures, operation may not be continued in the tunnel until it is confirmed that there are no longer any danger.
(2) The Contractor shall make regularly inspection and record of the harmful gas with automatic detection and recording instrument/equipment provided. The recording data shall be submitted to the Engineer for checking. Harmful gas in the tunnel must not exceed the standard prescribed in Sub-clause 507.03-1(2).
(3) For construction in tunnels with harmful gas, alarm and analytical instrument for continuous monitoring of combustible gas and harmful gas shall be installed. The alarm is able to visually alarm and also auditory alarm.
(4) The Contractor shall provide his personnel with various necessary safety tools or instrument, safety lamp, gas mask and oxygen supplying equipment in the area where harmful gas is possible to appear.