Известия Томского политехнического университета: Инжиниринг георесурсов (Nov 2017)
Unlocking a potential of district heating network efficient operation and maintenance by minimizing the depth of a trench system
Abstract
Relevance. The poor-quality of utilities causes the need to repeat excavation and reinstatement over their lifetime (up to 25 years) and therefore adds many longer-term costs relating to sustainability costs. For example, maintenance works are carried out within the deepbury district heating networks therefore increasing significantly the size of working areas (above ground) and requirements for equipment (e.g. heavy machinery), labour and materials. The aim of the research. Numerous problems are now encountered with such systems. Suitable design and installation guidelines were eventually developed which, when followed, gave no reasonable assurance of satisfactory service. In order to fill this need, we have undertaken a study to develop some guides for current systems. Methods. We are reasonably aware of the key concepts of systems thinking to describe and understand the forces and interrelationships that shape the behavior of the system. The object is appendixes related to inspection acts, projects of Omsk heat transmission enterprise with emphasis to the system layout profiles showing: all system stationing numbering, system slope drawn to scale to all low points, new and existing grade, all existing and new utilities shown at their actual burial depths; and a few detailed soil surveys made for capital projects in Omsk. Results. Concrete trench floors shall be sloped at 2 meters in 1000 meter slope toward all low points to ensure proper drainage. This, and existing or new utilities at their actual burial depths lead to a low grade of buried systems. The grading design should ensure ground water will not pond or sit over the trench. The trench should not be routed through the existing flood plains, swales, or in areas where seasonal water are accumulated. In areas where seasonal ground water may cause a trench flotation problem, the design that will include a subdrainage system along the trench if thickening of the system walls and floor slabs to offset the buoyancy effect is not practical. The systems with the floor, usually about 2 meters below surface-grade elevation, emerged in the 1930s and dominated all new systems until the 1990s. Today, such systems are largely covered with soil and sloped independently of topography may be considered as an outdated technology. Conclusions. It is an important challenge to gain the knowledge from placing electricity cables above district energy system and consequent catering disturbance claims for repeated excavation and reinstatement procedures. The installers of district heating should consider the location, spacing and depth of cover to avoid potential conflict with other existing underground apparatus. Heat distribution systems should be spaced to minimize the depth of the trench. The trench should be sealed to minimize the influx of ground water. Waterproof membranes should be placed in or below the concrete bottom slab and should be continued up the outer sides to the top of the sidewalls in accordance with the valve manhole guide specification. The top is constructed of reinforced concrete covers that protrude slightly above the surface and may also serve as a sidewalk.
