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Tong L.,Nanjing Southeast University | Liu L.,Mott MacDonald Group | Yu Q.,Guangdong Road & Bridge Construction Co.
Bulletin of Engineering Geology and the Environment | Year: 2014

Due to rapid expansion of the highway network in southern China in recent years, abandoned mine areas have been increasingly considered for highway construction. It is particularly challenging to carry out the assessment and remediation of mining subsidence effects on highway infrastructures, including high-filling embankments, deep-cutting slopes, and bridges. This article describes the subsidence mechanisms of abandoned mines with longwall workings and room-and-pillar systems, and also the potential geohazards and risks associated with abandoned mines. A hazard zonation criterion adopted for highway design and construction in China is introduced, as well as the possible remedial measures that can be carried out for various highway infrastructures. In the case study, grouting was used to fill cavities and stabilize the voids, and a two-layered geogrid was incorporated in the sub-base and embankment to avoid subsidence or sudden collapse of the ground. The remedial measures applied to deep-cutting slopes involved grouting, an anchor, or grid beam, employed either alone or in combination. In addition, a reinforced soil-piled embankment was utilized to reduce differential settlement at the transition zone between a bridge abutment and embankment. Based on the experiences gained, recommendations for future projects are given. © 2013, Springer-Verlag Berlin Heidelberg. Source


Tong L.,Nanjing Southeast University | Liu L.,Mott MacDonald Group | Cai G.,Nanjing Southeast University | Du G.,Nanjing Southeast University
Engineering Geology | Year: 2013

Determination of earth pressure coefficient K0 in natural soil deposits is a significantly important issue in geotechnical engineering. This paper evaluates the feasibility of predicting K0 values from measurements of vertical and horizontal shear wave velocities [Vs(VH), Vs(HH), and Vs(HV)], and vertical and horizontal electrical resistivities (SV, SH). A series of seismic piezocone tests (SCPTU), improved crosshole (CH) tests, and soil resistivity tests using a modified laboratory apparatus were carried out at two research sites in Jiangsu Province of China and results were used to develop two existing K0-shear wave velocity correlations for prediction of K0. The seismic and electrical resistivity test results showed that both the shear wave velocity ratios, Vs(HH)/Vs(HV) or Vs(HV)/Vs(VH), and the horizontal to vertical electrical resistivity ratio, SH/SV, may provide a good indicator of the inherent soil anisotropy at these sites. The existing Vs-K0 prediction framework largely requires determining Cs(HV)/Cs(HH) ratio and a simple procedure for evaluating this ratio based on the measured horizontal and vertical electrical resistivities. The K0 values predicted by shear wave velocity at both sites are also compared with values determined by Jaky's formula and Mayne & Kulhwy's formula. In normally consolidated (NC) soils, the K0 values predicted from these methods showed good agreement. However, for over-consolidated (OC) soils at shallow depths, certain variations between different methods are noted. Further investigations of the effects of overconsolidation ratio on K0 predictions will lead to the correction factors for better prediction of K0 for OC soils. This paper has confirmed that reasonable predictions of K0 for natural soil deposits can be made using the proposed methodology. © 2013 Elsevier B.V. Source


Tong L.,Nanjing Southeast University | Liu L.,Mott MacDonald Group | Qiu Y.,Guangdong Road and Bridge Construction Co.Ltd. | Liu S.,Nanjing Southeast University
Tunnelling and Underground Space Technology | Year: 2013

The tunnel design and construction in abandoned coal mine areas confront many challenges. Because of the historical reasons as well as complicated geologic and mining features, it is difficult to track and predict the locations, dimensions and geometry of the abandoned mine workings. The typical problems during the construction are always related to residual voids, mine water, infillings and gases. In this paper, a series of conceptual intersection models for risk assessment are discussed, and each model is characterized by a combination of tunneling problems. This paper also presents a risk assessment methodology, which links various intersection models to potential geo-hazards. A discussion on the engineering solutions in order to cross abandoned mine workings is also presented. Based on lessons learned from case histories in China, a flow chart for assessing support requirements in abandoned mine workings is proposed. Therefore this paper provides a framework to assess and reduce the geo-hazards associated with tunneling in abandoned mine areas and some applicable remediation techniques are proposed. © 2013 Elsevier Ltd. Source


Tong L.,Nanjing Southeast University | Liu L.,Mott MacDonald Group | Yu Q.,Guangdong Road and Bridge Construction Co.
Bulletin of Engineering Geology and the Environment | Year: 2013

Due to rapid expansion of the highway network in southern China in recent years, abandoned mine areas have been increasingly considered for highway construction. It is particularly challenging to carry out the assessment and remediation of mining subsidence effects on highway infrastructures, including high-filling embankments, deep-cutting slopes, and bridges. This article describes the subsidence mechanisms of abandoned mines with longwall workings and room-and-pillar systems, and also the potential geohazards and risks associated with abandoned mines. A hazard zonation criterion adopted for highway design and construction in China is introduced, as well as the possible remedial measures that can be carried out for various highway infrastructures. In the case study, grouting was used to fill cavities and stabilize the voids, and a two-layered geogrid was incorporated in the sub-base and embankment to avoid subsidence or sudden collapse of the ground. The remedial measures applied to deep-cutting slopes involved grouting, an anchor, or grid beam, employed either alone or in combination. In addition, a reinforced soil-piled embankment was utilized to reduce differential settlement at the transition zone between a bridge abutment and embankment. Based on the experiences gained, recommendations for future projects are given. © 2013 Springer-Verlag Berlin Heidelberg. Source


Tong L.,Nanjing Southeast University | Leo L.,Mott MacDonald Group | Amatya B.,Halcrow | Liu S.,Nanjing Southeast University
Bulletin of Engineering Geology and the Environment | Year: 2015

The influence of abandoned mine subsidence on transportation facilities is a growing concern due to rapid urbanization and industrialization in China. Transportation infrastructures are being or will be developed in many areas with potential subsidence problems. Consequently, it is necessary to assess and mitigate the long-term and progressive residual subsidence effects on transportation facilities in such regions. This paper presents an integrated framework to identify and mitigate the risks of abandoned mine subsidence on highway infrastructures. The framework comprises four steps: comprehensive investigations of abandoned mine features; identification of subsidence mechanisms, conceptual model construction and risk assessment; optimization of remedial solutions and development of a management strategy. A case study that demonstrates a successful application of the framework is also presented in this paper. In this example, a technique that integrates remote-sensing analysis throughout surface features with conventional investigation methodologies is proved to be a potential tool to detect and understand areas that might be at risk of surface subsidence. Based on the analysis of the representative failure mechanisms observed in situ and the influencing factors, a methodology has been developed to assess the geohazards associated with mine subsidence. Moreover, the proposed criteria for stability classification allowed us to define three geohazard levels on a regional scale. Subsequently, based on a brief review of remedial works made in China, the paper gives some recommendations to identify the most appropriate solutions to mitigate residual subsidence risk on transportation infrastructures. Such integrated decision-making framework will assist practitioners and regulators in identifying the potential risks of residual subsidence on transportation routes, optimising the most appropriate alignments, and assessing risk management practices. © 2015 Springer-Verlag Berlin Heidelberg Source

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