A study on the response of underground pipes due to blast loads

Olarewaju Akinola Johnson (2013) A study on the response of underground pipes due to blast loads. Doctoral thesis, Universiti Malaysia Sabah.

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Abstract

Underground pipes are used for services. Loads emanating from blast can create sufficient tremors to damage substructures over a wide area. Blast loads from explosives translate to loadings which the explosive charge (i. e. from surface blast or underground blast) delivers to the buried structures whether in the form of pressure or loading wave velocity. The main sources of blast are war, accidental explosion from military formation, etc. This study is aimed at determining the response of empty underground pipes due to blast loads by simulation using finite element method. Different types of blast and blast loads ranging from 10 kg TNT to 250 kg TNT were considered in this study. Using Unified Facilities Criteria (2008) for surface blast and analytical method for underground blast for the commonly used explosives at various stand-off points, ground movement parameters were determined. In this study, soil and pipe materials were considered as elastic, homogeneous and isotropic. Geotechnical and material properties as revealed by several researchers and pipe manufacturers were used. After validating existing model studied using SAP-80, response of underground pipes due to various categories of blast were studied using time integration technique in ABAQUS/Explicit, a finite element numerical code. Displacement, pressure, stress, strain at the crown, invert and spring-line of underground pipes buried at different embedment ratios in loose sand, dense sand and undrained clay were computed. Parametric studies were carried out and the results of the various responses were analyzed using dimensional analysis. Various mitigation measures were also suggested. In the whole work, a total of 639 models were analyzed. From the result of this study, blast load parameters estimated could be used in the evaluation of blast loads for design of underground pipes to resist the effects of blast loads. In addition, depths play a prominent role in the response of underground pipes due to blast loads. With increasing depth of burial of pipes, observed parameters reduced. These observed parameters reduced at embedment ratios of 3 to 5 for the blast scenarios considered. In addition to this, the reduction in the observed parameters of the response of underground pipes due to blast loads is more in loose sand compared to dense sand. As a result of this, loose material in the form of tire-chip backfill round the buried pipes could be used to mitigate the consequence of blast loads on underground pipes. Furthermore, undrained clay was observed to be problematic because the reduction in the observed parameters is least in the pipes buried in undrained clay and as a result of this, grouting and ground improvement techniques could be adopted as mitigation measure. In addition, for underground steel pipes to resist the effects of internal explosion, minimum of 20 mm thick is recommended. Finally, coefficient of friction of average of 0.4 could be used for the design of pipes buried in sand while coefficient of friction of average of 0.8 could be used for the design of pipes buried in undrained clay. The findings of this study will contribute to the existing academic literature, locally and internationally, considering the fact that this is a new area of research. The guidelines arrived at in this study can be applied by practicing engineers and professionals for design of underground pipes to resist the effects of blast loads. In addition to this, attention to be given to undrained clay soil that can be problematic in the design of underground pipes is also highlighted. In the case of underground pipes that are already designed and constructed without consideration to the effects of blast loads, mitigation measures pointed in this study will help in reducing the impact of blast loads.

Item Type:	Thesis (Doctoral)
Keyword:	Blast loads, Underground pipes
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA1-2040 Engineering (General). Civil engineering (General) > TA630-695 Structural engineering (General)
Department:	FACULTY > Faculty of Engineering
Depositing User:	DG MASNIAH AHMAD -
Date Deposited:	04 Dec 2024 15:13
Last Modified:	04 Dec 2024 15:13
URI:	https://eprints.ums.edu.my/id/eprint/41798

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