Accidents Investigation and Cause Analysis of Urban Underground Pipelines in Beijing

Research Article

Austin Public Health. 2017; 2(1): 1010.

Accidents Investigation and Cause Analysis of Urban Underground Pipelines in Beijing

Xingmeng G and Chunyan D*

Guizhou Minzhu University, P.R. China

*Corresponding author: Diao Chunyan, Guizhou Minzhu University, Guiyang, Guizhou, P.R. China

Received: September 15, 2017; Accepted: October 13, 2017; Published: October 20, 2017


Underground pipeline accidents and the reasons why these accidents occurred are studied in this paper. First, introduce the overview of the underground pipelines in Beijing. Then, investigate pipelines of gas, heat, water, rain water, sewage, recycled water, electricity, oil, lighting, communication and information, radio and TV broadcasting using statistical data. Third, from the accident statistics, propose and rank the causes of the pipeline accident with different pipelines. At the end of this paper, we conclude that the accidents caused by construction of other projects hold the first place, accounting for 48.9% of the total amount of the accidents; followed by the underground pipeline accidents due to aging and corrosion, accounting for nearly 34.5% of the total amount of the accidents; the accidents caused by the interaction between underground pipelines account for 6% of the total amount of the accidents; besides, the pipeline accidents caused by the poor quality of some pipelines and ground subsidence also account for a certain proportion.

Keywords: Pipeline; Cause analysis; Accident investigation


Modern society relies on a hidden network of tunnels, pipelines, and underground structures to transport people, cargo, liquids, and gasses from place to place, or to store materials, without disrupting surface activities or intruding on our views of the landscape [1]. This underground infrastructure is taken for granted until an extraordinary event occurs, such as a tunnel collapse or pipeline explosion. It aims at the rescue, repair, and restoration efforts; specialists from a variety of disciplines investigate the materials, design, and underground environment of the damaged facility [2-3] to determine the cause(s) of the failure and appropriate methods of repair.

Throughout recorded history, works have been constructed for conveying water from one place to another [5]. The Roman aqueducts are often mentioned as examples of great technical achievement [6]. Indeed, part of the early structure is still in use nowadays. Although most of the early water carrying structures were open channels, conduits and pipes of various materials were also used in Roman times. It appears, though, that the effectiveness of the early pipes was limited because their materials were weak in tensile capacity [7]. Therefore, the pipes could not carry fluid under any appreciable pressure. At the beginning of the 17th century, wood and cast iron [8] were used in water pipe applications in order to carry water under pressure from pumping, which was introduced about the same time. Since then, many materials have evolved for using in pipes. As a general rule, the goals of developing new pipe material are to increase tensile strength, reduce weight, and, of course, reduce cost [9-11]. Pipe that is buried underground must sustain other loads besides the internal fluid pressure. That is, it must support the soil overburden, ground water, loads applied at the ground surface, such as vehicular traffic, and forces induced by seismic motion. Therefore, the buried pipe is a kind of structure [12-13], but also the pipeline conveying fluid. In this case, special design procedures are needed to ensure that the two functions are met.

Theory and Method

Pipelines are used in public water systems, sewers, drainage facilities and many industrial processes. The materials of tubes used to be considered including steel, concrete and fiberglass reinforced plastics. This selection provides examples of flexible and rigid behavior. The method described here can also be applied to other materials.

Most of the design procedures provided are recommended practices based on materials or industry organizations contained in U.S. national standards. We intend to provide the basic elements of various design procedures. No claim has been made for the overall inclusiveness of the methodology discussed. Encourage comprehensive refinement of any method and the subtle interest of the reader to reference the works. For the sake of convenience, when comparing references, the symbols used in other work will be retained. Focus on large diameter lines, generally greater than 24 inches. Include work sample questions to illustrate the material provided.

The underground pipelines described here include natural gas, hot water, water, rainwater, sewage, circulating water, electricity, oil, lighting, communications and information, radio and television and other urban infrastructure underground pipelines [14-16]. By the end of 2006, the underground pipeline in Beijing has a total length of 41141.314km (901.081km) [17-20].

External loads

Overburden: The vertical load on the tube bracket extends from the ground to the top of the tube through a piece of soil and then adds (or subtracts) the shear force along the edge of the block.

Shear forces are produced when the surrounding soil, prisms, or prisms correspond to each other. For example, the soil prism above the pipe in the excavated trench will tend to be relative to the surrounding soil settlement. The shear force between the backfill and undisturbed soil will resist settlement, thereby reducing the prism load borne by the pipe. For pipelines placed on the ground and covered by new fillers, the effect may be the same or the opposite, in which case the load supported by the pipe will be greater than the soil prism. Behavioral differences depend on the difference in sedimentation between the pipe itself and the filler material.

Marvin and Spangler and their colleagues at the Iowa State University [21-22, 23-28] developed methods were used to assess the overburden loads of buried conduits over a period of about 50years and were widely used in design practices. The general form of the expression developed by this group is used to calculate the load of overburden for pipeline loading is given as

Wc = DCwB2 (1)


Wc: D total load on pipe, per unit of length

C: D load coefficient, dependent on type of installation, trench or fill, on the soil type, and on relative rates of settlement of the pipe and surrounding soil

w: D unit weight of soil supported by pipe,

B: D width of trench of outer diameter of pipe.

For different installation conditions, the value of the load factor C is given in several standard references (see for example [29]). The American Water Engineering Association (AWWA) [30] in its steel pipe design manual, it is suggested that the total overlying load of the buried steel pipe be assumed to be a soil prism equal to the diameter of the pipe, and the height of the equal covering depth.

That is,

Wc= DwBch (2)


Bc: D external pipe diameter,

H: D depth from ground surface to top of pipe.

Surcharge at grade: In addition to the direct load exerted by the soil cover layer, the underground pipelines must withstand the load exerted on the ground. Usually, the load is due to the route of the vehicle through the pipeline. However, they may be caused by electrostatic objects placed directly above the pipe.

The experimental results of [27,31], a researcher at Iowa State University, confirm that the load strength of the tube depth can be predicted according to the elastic theory because of the surface load. As an influence function, it is possible to obtain the effect of the Boussinesq solution [32] on the arbitrary spatial distribution of the surface load on the point load in the elastic half space. Because the stress distributions provided by the Boussinesq solution decay with the distance load, the strength of the surface load decreases with the increase in depth.

Consequently, the consequences of traffic or other surface loads on deep buried pipelines are relatively small. On the contrary, the surface load exerted on a pipe with a shallow cover may be quite serious. For this reason, the minimum protection is usually required where any ground runs through the underground pipeline.

Prior to the development of modern computing tools, the evaluation of the Boussinesq equation determined that the total load of the buried Tube was beyond the capacity of most practitioners due to arbitrary surface loads. Therefore, based on the simple surface load distribution developed the table, and has been incorporated into most of the buried tube design documents for many years.

For example, Mathcad [33] can be used to perform the necessary analysis to assess the impact of arbitrary surface loads on buried structures, including pipelines.

Live loads: The main source of live load for buried pipelines is the wheeled passage of road trucks, railway locomotives and aircraft. Using the standard HS-20 truck load [34] Cooper E-80 Railway load transmission to the load of the buried structure has been evaluated using the Boussinesq solution and engineering judgment, for different coverage depths, which can be in different forms several publications (see, for example [35,36]). Since the aircraft wheel loads vary greatly, it is usually necessary to evaluate each case separately. FAA Advisory Circular 150/5320-5B provides information on aircraft wheel loads. The load strength of pipeline depth has been reported in many references. Table 1 and Table 2 give the simple load strength of HSHeight 20 truck load and Cooper E-80 locomotive load at different depths [37]. More comprehensive forms of truck and rail cargo have been published [38,39].