Buried Concrete Pipes Research Articles

Time-Variant Performance of Concrete Sewer Pipes Undergoing Biogenic Sulfuric Acid Degradation

AbstractThe paper presents a methodology for the advanced design of buried concrete pipes or assessment of their performance that enables realistic decisions to be taken concerning the safe and cos...

Economical design of buried concrete pipes subjected to UK standard traffic loading

The British standard (BS) uses the indirect design method to design buried concrete pipes under the effect of traffic load; in this method the laboratory capacity of the pipe is obtained and linked to the field capacity using an empirical factor called the bedding factor. However, the BS design bedding factors have not been rigorously tested. This paper therefore presents a rigorous analysis of the response of buried pipes under the BS traffic loading requirements and tests the robustness of the BS design bedding factors using a validated finite-element model. It was found that the BS bedding factors are overly conservative, with a ratio of calculated values to the design bedding factors ranging from 1·63 to 4·92. This over-conservatism can be attributed to an oversimplification in the BS methodology for calculating the force applied to the pipe. Therefore, new bedding factors have been proposed utilising the evolutionary polynomial regression analysis technique. These bedding factors implicitly account for the error due to the oversimplification in the design force calculation. Hence, more economical and robust designs can be achieved by using the new bedding factors.

Development of a novel model to estimate bedding factors to ensure the economic and robust design of rigid pipes under soil loads

Buried concrete pipes are load bearing structures that need to resist the loads imposed by the surrounding ground. The common approach to design buried concrete pipes is based on an empirical method called the Indirect Design Method, which uses the laboratory capacity of the buried pipe linked to the field capacity using an empirical factor known as the bedding factor. However, limited published studies have investigated this bedding factor or tried to improve the current bedding factor values. Therefore, this study investigated the bending moment and bedding factor for concrete pipes under soil loads by conducting a parametric study investigating the effect of the installation condition, pipe diameter, pipe thickness and backfill height. A validated finite element model has been used for this purpose. The bedding factors obtained from the analyses have been compared with the bedding factors currently adopted by the AASHTO and British Standard (BS) design standards. The results showed that the BS design standard is conservative. In addition, the AASHTO design standard has been shown not to be safe for pipes with a diameter of 0.3 m and becomes more conservative as the diameter increases or the installation quality decreases. Therefore, new bedding factor models have been proposed using the results of the finite element modelling utilising an evolutionary polynomial regression (EPR) method. The paper demonstrates that the new models could be used for the economic and robust design of concrete pipes. The proposed models in this paper have the potential to significantly reduce the costs involved in either construction or maintenance of buried concrete pipes.

Investigation of influence the pressure and stress on the water in buried concrete pipes in the different soil under blast loading

Investigation of influence the pressure and stress on the water in buried concrete pipes in the different soil under blast loading

Stress Distribution of Buried Concrete Pipe Under Various Environmental Conditions

There are numerous factors that affect stress distribution in a buried pipe, such as the shape, size, and stiffness of the pipe, its burial depth, and the stiffness of the surrounding soil. In addition, the pipe can benefit from the soil arching effect to some extent, through which the overburden and surcharge pressure at the crown can be carried by the adjacent soil. As a result, the buried pipe needs to support only a portion of the load that is not transferred to the adjacent soil. This paper presents numerical efforts to investigate the stress distribution in the buried concrete pipe under various environmental conditions. To that end, a nonlinear elasto-plastic model for backfill materials was implemented into finite element software by a user-defined subroutine (user material, or UMAT) to more precisely analyze the soil behavior surrounding a buried concrete pipe subjected to surface loading. In addition, three different backfill materials with a native soil were selected to examine the material-specific stress distribution in pipe. The environmental conditions considering in this study the loading effect and void effects were investigated using finite element method. The simulation results provide information on how the pressures are redistributed, and how the buried concrete pipe behaves under various environmental conditions.

A gamma distributed degradation rate model for reliability analysis of concrete pipes subject to sulphide corrosion

Ageing and deterioration of structures and infrastructure is one of the main concerns of structural engineers and asset managers for reliability analysis and service life prediction purposes. In order to model monotonic progression of the deterioration process in concrete sewers (i.e., concrete corrosion), the paper proposes a gamma distributed rate model to account for temporal variability associated with the corrosion process in buried concrete sewer pipes that typically increases the probability of failure with the ageing of the pipe. The proposed methodology is used for reliability analysis of concrete sewers in Harrogate in the UK. The results are then verified by a common reliability analysis method (i.e., Monte Carlo simulation). A good agreement between the results from the two methods was concluded. The effectiveness of different basic random variables on the level of reliability is also estimated by a focused sensitivity analysis.

교통하중하의 지하 매설관의 거동 평가

지하 매설관은 우리의 일상생활과 매우 밀접하지만 일반적으로 붕괴로 인한 피해가 발생하기 전에는 그 중요성에 둔감한 편이다. 대부분의 매설관은 도로포장체 아래에 매설되어 있어 외부하중으로는 주로 교통하중을 받는다. 본 연구에서는 이러한 교통하중을 받는 지하 매설관의 거동에 대해 살펴보았다. 지하 매설관의 거동에 영향을 미치는 인자는 여러 가지가 있지만, 본 연구에서는 매설 깊이(H)와 매설관의 직경(D)의 비를 가장 중요한 인자로 보고 연구를 수행하였다. 두 가지 경우의 매설 깊이에 대한 매설관 직경 비에 따른 매설관의 건전성을 살펴보았다. 결과를 바탕으로 매설관의 건전성을 확보할 수 있는 매설깊이를 결정할 수 있었으며, 보다 경계적인 매설관 설계를 할 수 있을 것으로 기대된다. Pipeline is very important infrastructure which is directly related to our daily life. Nevertheless, it is not considered significantly unless it breaks. As most pipelines are buried at a certain depth from the surface of road pavement in urban areas, they are subjected to traffic load. This paper presents the performance of buried concrete pipe under heavy traffic load. Hence, one of the major factors affecting their performance is burial depth. To consider this factor, the ratio of burial depth (H) to diameter of pipe (D) was defined as a key variable. The integrity of buried concrete pipe was investigated with two cases of ratio of burial depth to pipe diameter (H/D=2 and H/D=4). The results provide the limit burial depth to ensure the soundness of buried concrete pipe subjected to heavy traffic load, and more economical design is anticipated with the results.

Fluid Jackets

To surround the circumference of plain concrete pipes with fluid jackets is a revolutionary concept that can result in maximum burial depths and live load capacities more than twice those of conventional, steel-reinforced concrete pipes. Moreover, the enhanced capacities are achievable with less than one-half the usual amount of concrete and with zero steel reinforcement. Alternatively, fluid jacketed concrete pipes may be designed with the same structural capacity as conventional reinforced concrete pipes but with a project cost savings that results from a 50% weight reduction per foot of pipe. These claims are supported by the analysis presented in this paper, which is a necessary first step before experimental validation can occur. Engineered plastic jackets encapsulate fluid (water) in a watertight configuration that encircles the buried concrete pipe. The encapsulated fluid transforms nonuniform soil pressure to uniform hydrostatic pressure around the pipe periphery. Consequently, the concrete pipe experiences hoop compression only, without the bending deformation and concrete cracking inherent in conventionally installed, reinforced concrete pipe. The fluid jacket concept has not been published in open literature. This paper illustrates the physics of the concept and presents the most promising configuration and materials determined through structural analysis studies with the CANDE-2007 computer program. Fluid jacket designs are proposed in this paper as a first step to bring this revolutionary idea to fruition. Next steps include laboratory testing, field testing, and modeling refinement.

On the detection of objects buried at a shallow depth using seismic wave reflections

This paper concerns the detection of shallow (of the order 1 m) buried objects using seismic excitation. Time-extended signals are used to generate a compressional wave using a shaker attached to the ground. The wave propagates through the ground, reflects off a buried object and is captured by an array of geophones on the surface. The envelopes of the cross-correlation functions between the measured ground velocities and the excitation signal are calculated and summed to generate a cross-sectional image of the ground. The wide cross-correlation peaks caused by high ground attenuation are partially compensated for by using the generalized cross-correlation function called the phase transform. Simple simulations are conducted to demonstrate the method, and some field experiments have been carried out aimed at the detection of a buried concrete pipe. In the experiments the pipe could be detected using the method proposed, with experimental and simulated data producing good agreement.

Soil-Structure Interaction and Imperfect Trench Installations for Deeply Buried Concrete Pipes

The imperfect trench installation method is used to reduce earth pressure on buried concrete pipes. Few quantitative refinements to the imperfect trench installation method, however, have been added since the fundamental mechanics of the reverse arching action were proposed by Marston and Spangler. There have been limited research results published regarding, primarily, qualitative aspects of earth load reduction for imperfect trench conditions. This paper identifies variables that significantly affect earth loads, as well as the effects of bedding and sidefill treatments. An optimum geometry for imperfect trench installations with regard to a soft material zone is presented to maximize the earth load reduction effects. The optimization process was based on parametric studies of the geometry and location of the soft zone, bedding, and sidefill treatments to reduce earth pressures. Predictor equations for earth load reduction rates were formulated incorporating the optimum geometry for the soft zone and bedding and sidefill treatments.

Segmentation of buried concrete pipe images

The enormity of the problem of deteriorating pipeline infrastructure is widely apparent. Since a complete rebuilding of the piping system is not financially realistic, municipal and utility operators require the ability to monitor the condition of buried pipes. Thus, reliable pipeline assessment and management tools are necessary to develop long term cost effective maintenance, repair, and rehabilitation programs. In this paper a simple, robust and efficient image segmentation algorithm for the automated analysis of scanned underground pipe images is presented. The algorithm consists of image pre-processing followed by a sequence of morphological operations to accurately segment pipe cracks, holes, joints, laterals, and collapsed surfaces, a crucial step in the classification of defects in underground pipes. The proposed approach can be completely automated and has been tested on five hundred scanned images of buried concrete sewer pipes from major cities in North America.

Automated detection of cracks in buried concrete pipe images

The detection of cracks in concrete infrastructure is a problem of great interest. In particular, the detection of cracks in buried pipes is a crucial step in assessing the degree of pipe deterioration for municipal and utility operators. The key challenge is that whereas joints and laterals have a predictable appearance, the randomness and irregularity of cracks make them difficult to model. Our previous work has led to a segmented pipe image (with holes, joints, and laterals eliminated) obtained by a morphological approach. This paper presents the development of a statistical filter for the detection of cracks in the pipes. We propose a two-step approach. The first step is local and is used to extract crack features from the buried pipe images; we present two such detectors as well as a method for fusing them. The second step is global and defines the cracks among the segment candidates by processes of cleaning and linking. The influences of the parameters on crack detection are studied and results are presented for various pipe images.

Field Performance of Instrumented Concrete Pipe Under Deep Burial

Two 1.524-m-diameter, reinforced concrete pipes were instrumented to compare field results with design calculations. A computer program, Standard Installation Direct Design, developed by the American Concrete Pipe Association was used to design the pipe. Instrumented pipes were completely monitored until 11.9 m of cover had been placed. Measurements of soil contact pressures and vertical and horizontal deflections continued for 6 months. The computer-simulated and observed responses of the buried concrete pipe installations were compared. Pipe contact pressures measured at the invert were much smaller than those assumed from calculations of thrust and moment. Design moments were conservative compared with the experimentally measured values. Thrusts are difficult to calculate accurately and show large experimental variations.

Buried Concrete Pipe Trench Installation Analysis

The conventional approach for determining load on buried concrete pipe for trench installation is summarized. A finite element computer model's capabilities are demonstrated by examining cases of trench installations for which some field experience is available. Comparisons are made between predictions using the conventional method and the new computer method. The conventional method estimated higher load on the pipe than the computer model for trench installations. This is partly because the conventional trench method neglects the support capability of the sidefill soil. The computer method is shown to have advantages over the conventional method in its ability to represent a variety of actual installation conditions and to provide information on soil pressure distribution needed for pipe design.

Buried Concrete Pipe Embankment Installation Analysis

The paper first summarizes the conventional approach for determining load on buried concrete pipe for embankment installations. A finite element computer method that provides a more precise and versatile approach to pipe design and analysis is then briefly described. The computer model capabilities are demonstrated by examining cases of embankment installations for which some field experience is available. Comparisons are made between predictions using the conventional method and using the new computer method. In general the conventional method estimated higher load on the pipe than the computer model. An exception was the induced trench installation. The computer method is shown to have advantages over the conventional method in ability to represent a variety of actual installation conditions and provide information on soil pressure distribution needed for pipe design.