Outcomes of the Newcastle symposium for the prediction of embankment behaviour on soft soil

Creep behaviour of an undisturbed lightly overconsolidated clay

The large amount of spoil material produced during the mining process imposes a significant economic and environmental liability on lignite producers. In this context, the present paper provides an overview of the geotechnical characteristics of European lignite mine spoil heaps and discusses their significance to the stability of the heaps. In order to achieve this, samples collected from spoil heaps of Polish, Czech and Greek mines are analysed and the results are compiled with data from the literature. A major conclusion drawn is that both physical and engineering properties of spoil heaps indicate a noteworthy variability, which is larger than typical in situ ground material. This is because of the additional factors affecting spoil heap deposition, such as the transportation and dumping method. Furthermore, failure mechanisms and case histories of large instabilities in lignite spoil heaps are critically discussed in order to better understand triggering failure mechanisms. It is concluded that classical assumptions made for natural soil slopes and relevant limit equilibrium models should be cautiously applied to spoil heaps. The challenges associated with numerical and probabilistic modelling of spoil heap stability, such as the inherent spatial variability of spoils and the time-dependent changes in their geotechnical properties, are also critically discussed. Finally, important research gaps in design and analysis of spoil heap stability, such as the absence of appropriate constitutive models developed specifically for spoil materials, are summarised.

/pdf/stability-and-characterisation-of-spoil-heaps-in-european-346pzosm1t.pdf

Stability and characterisation of spoil heaps in European surface lignite mines: a state-of-the-art review in light of new data

This paper presents an exhaustive review of the challenges faced in the construction of road embankments on soft ground and proposes a direction for future development. Frequently used techniques for soft ground improvement are discussed. The factors that contribute to the stability of the road embankment are reviewed by approach, results of past studies, and historical cases. The findings show that settlement, slope stability, and soil bearing capacity are all challenges to constructing the road embankment. Additionally, it is found that geometric data is a key factor in embankment design. Preloading with prefabricated vertical drain (PVDs) methods and lightweight fill were found to be widely used techniques in soft ground improvement. The information from this study can be used to develop design guidance systems, numerical modelling, and to give an overview and knowledge to other researchers who are or will conduct research in this field. Finally, future perspectives for research are related to predictions of factors that affect the stability of road embankment with an artificial intelligence approach. ABSTRAK: Kertas ini membentangkan ulasan kajian menyeluruh mengenai cabaran yang dihadapi dalam pembinaan benteng jalanraya di atas tanah lembut dan mencadangkan ke arah pembangunan kajian masa depan. Teknik-teknik penambahbaikan tanah lembut yang sering digunakan turut dibincangkan. Faktorfaktor yang menyumbang kepada kestabilan benteng jalanraya diulas dengan pendekatan kepada kajian lepas dan sejarah kes. Hasil kajian ini didapati bahawa enapan, kestabilan cerun dan keupayaan galas tanah merupakan cabaran dalam pembinaan benteng jalanraya. Selain itu, ia didapati bahawa data geometri merupakan faktor penting kepada rekabentuk benteng. Kaedah pra pembebanan dengan prefabrikasi saliran menegak (PVDs) dan isian ringan didapati teknik yang popular digunakan dalam pembaikkan tanah lembut masa kini. Maklumat dari kajian ini boleh digunakan untuk membangunkan sistem panduan reka bentuk, pemodelan berangka serta memberi gambaran dan ilmu kepada penyelidik lain yang sedang atau akan menjalankan kajian dalam bidang ini. Akhir sekali, perspektif masa depan untuk penyelidikan berkaitan ramalan faktor-faktor yang mempengaruhi kestabilan embankment jalanraya dengan pendekatan kepintaran buatan.

/pdf/a-review-of-road-embankment-stability-on-soft-ground-2ycatcu3rl.pdf

A review of road embankment stability on soft ground: problems and future perspective

In landslide analysis, reliable prediction of landslide’s influence zone is significantly difficult due to inherent heterogeneity of soils and their spatially varying geological properties. In this paper, a probabilistic framework is proposed to evaluate the landslide hazard zoning through prediction of their influence zone considering the effects of heterogeneous soil properties. Material point method is used to simulate the large deformations during landslide failure. The spatial variation in the shear strength parameters of soils at undrained conditions is modeled by random fields, which are discretized by Cholesky matrix decomposition method to incorporate the effects of the soil spatial heterogeneity on the post-failure deformations. Furthermore, a practical landslide hazard zoning is conducted to quantitively evaluate the level of disaster for facilities or structures located in the vicinity of the slope by using the exceedance probability of influence distance and runout distance. Five categories based on different thresholds of exceedance probability are used to visualize the area potentially affected by the landslide. To demonstrate the capability of the stochastic

/pdf/stochastic-assessment-of-landslide-influence-zone-by-1qxvnsdy.pdf

Stochastic Assessment of Landslide Influence Zone by Material Point Method and Generalized Geotechnical Random Field Theory

Numerical analysis of Ballina test embankment on a soft structured clay foundation

Dynamic fluctuations in the PV-source power and different DC-fault scenarios in the off-grid PV-battery-based DC microgrid could lead to a rapid decrease in the reliability of the PV-generating system. To make this viewpoint clearer, this paper proposes a novel reliability-evaluating methodology for PV-generating systems in the islanded DC microgrid under dynamic and transient operation conditions. Firstly, the dynamic-voltage-varying failure rate (DVVFR) and the fault-current-varying failure rate (FCVFR) of a PV-generating system in the off-grid DC microgrid are formulated. The DVVFR mainly depends on dynamic fluctuations in the PV-source power and the load power, whereas the FCVFR mostly represents the failure probability due to pole-to-pole and pole-to-ground faults in the DC microgrid. Then, a possible combination of the used-time-varying failure rate (TVFR), the power-loss and temperature-dependent failure rate, the DVVFR, and the FCVFR is proposed for evaluating the system-level and component-level reliability of PV-generating sources. Finally, Markov-state transition diagrams and Chapman–Kolmogorov equations are derived and applied for the PV-system reliability assessment in the off-grid PV-battery-based DC microgrid. Experimental results are analysed to reveal that the operation of DC-DC power converters dominates the PV-system reliability under the dynamic and transient operation. The DVVFR of the PV system is mostly smaller than its FCVFR, however, the system-level reliability of the PV-generating source is significantly reduced by dynamic-voltage-fluctuating cases due to the more frequent repetition of these dynamic cases. Moreover, the MTTF and MTBF of the PV-generating system could also be dramatically decreased by the dynamic and transient operation of the DC microgrid. 

Reliability analysis of PV generating systems in the islanded DC microgrid under dynamic and transient operation

Boost-converter reliability assessment for renewable-energy generation systems in a low-voltage DC microgrid

Reliability assessment of bidirectional power converters in battery energy storage systems of the DC microgrid

Pervious concrete pavement has been used widely as an effective practice for water management in low-impact development techniques. The hydrologic performance of pervious concrete pavement depends significantlyon the rainfall intensity and the designed slope. This study assessed the hydrologic performance of pervious concrete pavement by evaluating the time for surface ponding via finite element analysis. A series of simulations were carried out to explore the relationship between hydrologic performance and pervious concrete pavement by the Hydrus 2D program. The research’s results showed that as the slope increased, the time of surface ponding also increased. The data indicated that the slope variable had a low impact on the water level in pervious concrete pavement under a constant rainfall intensity. Observation of the effect of rainfall intensity showed that when the rainfall intensity increased twofold, the time for surface ponding dropped about two times. Furthermore, when surface ponding appeared, pervious concrete pavement at higher rainfall intensity had lower water content. The rainfall intensity also significantly affects the hydrologicperformance of the pervious concrete pavement. This study only assessed the hydrologic performance by using the time for surface ponding via finite element analysis. Further experimental studies should be conducted to examine the relationship of other factors to the hydrologic performance of pervious concrete pavement.

/pdf/investigation-on-hydrologic-performance-of-pervious-concrete-2wbh3xnu.pdf

Hung Nguyen

Papers

Numerical analysis of Ballina test embankment on a soft structured clay foundation

Reliability analysis of PV generating systems in the islanded DC microgrid under dynamic and transient operation

Boost-converter reliability assessment for renewable-energy generation systems in a low-voltage DC microgrid

Reliability assessment of bidirectional power converters in battery energy storage systems of the DC microgrid

Investigation on hydrologic performance of pervious concrete pavement by finite element analysis