1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T L.155 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2016) SERIES L: ENVIRONMENT AND ICTS, CLIMATE CHANGE, E-WASTE, ENERGY EFFICIENCY; CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE P
2、LANT Optical fibre cables Guidance and installation technique Low impact trenching technique for FTTx networks Recommendation ITU-T L.155 ITU-T L-SERIES RECOMMENDATIONS ENVIRONMENT AND ICTS, CLIMATE CHANGE, E-WASTE, ENERGY EFFICIENCY; CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELE
3、MENTS OF OUTSIDE PLANT OPTICAL FIBRE CABLES Cable structure and characteristics L.100L.124 Cable evaluation L.125L.149 Guidance and installation technique L.150L.199 OPTICAL INFRASTRUCTURES Infrastructure including node element (except cables) L.200L.249 General aspects and network design L.250L.299
4、 MAINTENANCE AND OPERATION Optical fibre cable maintenance L.300L.329 Infrastructure maintenance L.330L.349 Operation support and infrastructure management L.350L.379 Disaster management L.380L.399 PASSIVE OPTICAL DEVICES L.400L.429 MARINIZED TERRESTRIAL CABLES L.430L.449 For further details, please
5、 refer to the list of ITU-T Recommendations. Rec. ITU-T L.155 (11/2016) i Recommendation ITU-T L.155 Low impact trenching technique for FTTx networks Summary With the miniaturization of the telecommunication infrastructure, i.e., with mini-ducts and mini-cables, it has been possible to use a low imp
6、act trenching technique to carry out all the steps of the network construction in a single day, in a less invasive way in terms of time and space, and with a smaller construction site than for the previous trenching technologies. Recommendation ITU-T L.155 describes this trenching technique, which a
7、llows the easy installation, in narrow trenches, of underground optical cables and mini-cables in ducts or mini-ducts or directly buried. This type of narrow trench allows the use of reduced dimension machinery in small-sized roads, typically those in cities, producing a lower quantity of waste mate
8、rial and so should be used in urban areas. This technology is mainly characterized by the simultaneous work of a suction machine and a trench saw, which allows for the possibility of opening and closing the work site the same day. History Edition Recommendation Approval Study Group Unique ID* 1.0 IT
9、U-T L.155/L.83 2010-07-29 15 11.1002/1000/10916 2.0 ITU-T L.155 2016-11-13 15 11.1002/1000/13113 Keywords Environmental low-impact, FTTx network, reduction, urban trenching technique. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, follo
10、wed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T L.155 (11/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologie
11、s (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunic
12、ation Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of
13、information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating
14、 agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or
15、 some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice
16、or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development
17、 process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore st
18、rongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2017 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.155 (11/2016) iii Table of Contents Page 1 Scope . 1 2 Refe
19、rences . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 1 5 Conventions 1 6 The urban trenching cable-laying technique . 2 6.1 Preparatory step 2 6.2 Excavation requirements 3 6.3 Working phases for laying the infrastructure
20、or cables 3 6.4 Identification . 4 6.5 Resurfacing . 4 6.6 Maintenance . 4 7 Daily urban trenching methods and procedures . 5 8 Daily urban trenching application criteria 5 8.1 Entry to existing manholes or chambers 5 8.2 Road crossings 5 9 Practical rules for the correct realization of micro-trench
21、es . 5 Appendix I Italian experience regarding “one day“ reduced mini trench . 7 Appendix II Effect of micro-trenches on road pavements 10 II.1 Scope 10 II.2 Study for the optimization of the performance of micro-trench/pavement system . 10 II.3 Effects of thermal strains on the performance of the m
22、icro-trench/pavement system . 13 II.4 Effects of the micro-trench on the drainage conditions of the roadway . 14 Bibliography. 15 Rec. ITU-T L.155 (11/2016) 1 Recommendation ITU-T L.155 Low impact trenching technique for FTTx networks 1 Scope This Recommendation: gives advice on general requirements
23、 of the main phases in which the work can be divided; gives advice on the methods and procedures for performing the work; gives some application criteria; describes situations where a low impact urban trenching technique is recommended. 2 References The following ITU-T Recommendations and other refe
24、rences contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to inv
25、estigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the s
26、tatus of a Recommendation. ITU-T L.260 Recommendation ITU-T L.260/L.84 (2010), Fast mapping of underground networks. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 urban trenching technique: It is charact
27、erized by a width of maximum 5 cm and typically a depth of maximum 30 cm. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: FTTx Fiber To The x, where x stands for the final location on the end-user side GPR3D Ground Penetration Radar 3 Dimensions NGN Ne
28、xt Generation Network 5 Conventions None. 2 Rec. ITU-T L.155 (11/2016) 6 The urban trenching cable-laying technique The urban trenching technique should be applied especially in urban areas, where car traffic and shop presence is very high and on routes that generally involve asphalted surfaces such
29、 as roads and sidewalks with a base of compact material (asphalt or concrete). It is not recommended that the technique be used on routes where the soil subgrade is sandy, gravelly or contains medium-sized cobbles (i.e., measuring 10 to 20 cm in diameter). The main advantages of this technique over
30、traditional cable-laying technologies are the very small obstruction of the road and the low impact on traffic due to the road construction site cleaning, the immediate removal of debris and the quickness of opening and closing the road construction site. The urban trenching technique is normally ca
31、rried out by simultaneously cutting through the paving and digging a trench whose depth and cross-section vary in accordance with the number of ducts to be laid: depth is 30 cm, while cross-section can be 5 cm. In order to guarantee a protection against impact resulting from road-repairing, the dept
32、h of the laid infrastructure should be maintained constant at a known level that should be 5 cm deeper than the foreseen asphalt cutting depth normally specified for road surface repair works. Figure 1 shows some possible duct and mini-duct installation configurations that can be used. Figure 1 Exam
33、ples of urban-trenching duct installation configuration Any crossings through unpaved sections (which should in any case have a compact subgrade) should be carried out using the same technique. 6.1 Preparatory step Generally, a detailed survey of the route should be carried out, the purpose of which
34、 is to identify the work required to be done before starting cable installation operations. Such work could include, for instance, the preparation at bridges, or at road or rail crossings. Further, it is necessary to determine closure locations and section ends. The location of all underground utili
35、ties should be determined in order to establish the correct route for the trench. This is normally accomplished by means of cartographic documentation provided by the administrations that own the road or by the utility company, and/or through instrumented field surveys. The detailed utilities invest
36、igation should be made with the ground penetration radar 3 dimensions (GPR3D) fast solution technique ITU-T L.260. The designed route should be free from sharp changes in direction. Where such changes are unavoidable, they should be made by means of cuts angled so as to comply with the minimum bend
37、radii specified for the ducts and cables. Where necessary, the contractor can take core samples along the planned route to determine the type of subsoil or as a further method of checking for obstacles. A GPR3D fast solution should be used in order to detect ground characteristics ITU-T L.260. Rec.
38、ITU-T L.155 (11/2016) 3 6.2 Excavation requirements The following requirements should be observed in cutting while applying the urban trenching technique: comply with all provisions and regulations established by the administrations involved as regards excavation permits, schedules, etc.; place the
39、barriers and road signs required by current legislation, regulations and the administrations involved, in clearly visible locations around the excavation site. Generally, the site is opened and closed during the same day, so the excavation should not remain open during the night. 6.3 Working phases
40、for laying the infrastructure or cables All the construction activities should be split in separate operational steps involving subsequent phases (Figure 2). This synergism should allow: flexible use of smaller machines; reductions of time and space occupancy. Figure 2 Daily reduced trenching techni
41、que logical scheme 6.3.1 Simultaneous trenching dig phase and cleaning phase It is recommended that the urban trenching technique be characterized by the simultaneous work of the trench saw and the suction machine. This combined action should allow the waste material to be collected while produced b
42、y the saw, leaving the site clean immediately after the end of the trenching phase and completely removing dust problems. 6.3.1.1 Trenching dig phase The urban trench should be made using a small size saw disk, mounted on small dimension operating machines. The trenching cut should not damage the ur
43、ban road pavement near the dig section. The saw should be inside a protective carter connected via a flexible tube to a vacuum pump installed on the suction machine. 6.3.1.2 Spoil suction phase The debris suction and the digging phase should be performed simultaneously in order to accelerate the tre
44、nch cleaning action. Spoil should be transported to authorized disposal sites in accordance with current local laws. The trench cleaning shall be made with automated methods in order to avoid or limit troubles to people and environmental pollution. At the end of this phase, the trench cross-section
45、should be completely free of stones and the bottom of the trench should be clean. The trench and the near zones should be completely clean of debris that could reduce the backfilling material features. 4 Rec. ITU-T L.155 (11/2016) 6.3.2 Ducts or cable laying The reel can be mounted aboard a machine
46、subsequent to the saw, so that the duct(s) or cable can be automatically fed into the trench, via a suitably shaped guide integrated into the ploughshare, as the excavation proceeds. The equipment and procedures used for this purpose should guarantee that: initial duct or cable configuration and pos
47、ition in the urban trenching technique are maintained along the entire route unless special circumstances dictate otherwise; if obstacles or situations are encountered which make it impossible to proceed with the urban trenching technique, the reel (and thus the ducts or the cable) can be removed fr
48、om the machine without having to cut the ducts, thus ensuring that cable deployment can be continued using conventional methods without performing splices that are unnecessary from the technical standpoint. 6.3.3 Backfilling phase After the ducts, mini-ducts or cables are installed, the trench shoul
49、d be backfilled with a highly resistant and fast-hardening material. The trench backfilling shall be made with rapid cement mortar casting. The mortar should be quick setting, with fluid consistency, containing cement with high strength, selected aggregate and special additives. Bitumen material shall be avoided. The backfilling material should have particular features in order to assure vehicle traffic restoration within two to four hours and it shall present high compatibility with mechanical and v
