Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Acta Geotechnica - Consolidation rate has significant influence on the settlement of structures founded on soft fine-grained soil. This paper presents the results of a series of small-scale and...     

Transformed equations of motion for underwater vehicles

A method for dynamics investigation and coupling detection between velocities of autonomous underwater vehicles (AUVs) is presented in this paper. The method is based on transformation of equations of motion, which are usually used for an underwater vehicle, into equations with a diagonal mass matrix. The obtained equations contain quasi-velocities and allow one to give a further insight into the AUV dynamics especially for an underactuated system. Some advantages of the proposed approach are discussed, too. An analytical example for a 3-DOF AUV shows possible application of the transformed equations. Moreover, the given approach is validated via simulation on a 6-DOF vehicle.     

Decoupled PD set-point controller for underwater vehicles

A set-point controller for autonomous underwater vehicles (AUVs) is proposed in this paper. The controller is expressed in transformed equations of motion with a diagonal inertia matrix. It takes into account the dynamics of the system and it can be applied for fully actuated AUVs. The stability of the designed control law is demonstrated by means of a Lyapunov-based argument. Some advantages arising from the use of the controller are considered too. The performance of the proposed controller is validated via simulation on a 6-DOF underwater vehicle.     

Origin and post-glacial evolution of surface cracks: A case study from the area of the Last Glaciation,north-eastern Poland

The analysis of LiDAR-based digital elevation models revealed the existence of groups of longitudinal fractures in the ground in northern Poland at the limit of the ice sheet's extent during its last maximum. Our research on the closed elongated depressions (CEDs) of the Jedwabno test field (Szuć site, north-east Poland) focuses on explaining their origins and their post-glacial history. This region was covered by an ice sheet and glacitectonically active during the Vistulian, and at least some surface fractures are possible witnesses to this activity. Using geomorphological mapping, sedimentological and geophysical research, we assumed it was related that the origin of these features here is associated with groundwater migration at the end of the Vistulian glaciation or later when groundwater flow intensified due to a rapid climate warming that caused permafrost to melt. The thawing of permafrost caused to transition from continuous permafrost to discontinuous, which in turn created groundwater flow that was probably responsible for the development of the surface cracks (fractures). Radiocarbon, palaeobiological (pollen, Cladocera) and geochemical studies allowed for an estimation of the formation time of these unique surface cracks in the Older Dryas. Prevailing conditions were also reconstructed for the later dynamic changes of the end of the Late Vistulian glaciation and in the Late Holocene until the Subatlantic Period (Megalayan stage). The surface cracks with steep slopes, despite their small area, are extraordinary sedimentation traps that have, in a special way, retained an almost complete record of the environmental and climate changes of the Late Glacial. There are sedimentological gaps in the Holocene, especially after the Preboreal (old part of the Greenlandian Stage), caused by changes in water levels, aeolian processes and human activity.     

Precambrian crustal contribution to the Variscan accretionary prism of the Kaczawa Mountains (Sudetes,SW Poland): evidence from SHRIMP dating of detrital zircons

SHRIMP dating of detrital zircons from sandstones of the Gackowa Formation (Kaczawa Complex, Sudetes, SW Poland) indicates input from late (550–750 Ma) and early Proterozoic to Archaean sources (∼2.0–3.4 Ga, the latter being the oldest recorded age from the Sudetic region). These dates preclude within-terrane derivation from seemingly correlatory acid volcanic rocks of early Palaeozoic age. Rather, they indicate provenance from Cadomian and older rocks that currently form part of other, geographically distant terranes; the most likely source identified to date is the Lusatian Block in the Saxothuringian Zone. Hence, the Gackowa Formation may be late Proterozoic rather than early Palaeozoic in depositional age, possibly coeval with the late Proterozoic (pre-Cadomian) greywackes of Lusatia, being subsequently tectonically interleaved with early Palaeozoic volcanic rocks into the Kaczawa accretionary prism during the Variscan orogeny. However, correlation with the lithologically similar early Ordovician Dubrau Quartzite of Saxothuringia, and so assignation to the early Paleozoic (post-Cadomian) rift succession deposited at the northern margin of Gondwana, cannot yet be precluded.     

Correlating specific conductivity with total hardness in gypsum karst waters

Modern digital conductivity meters are readily portable, robust, cheap, and give precisely reproducible values of specific electrical conductivity (SpC, in µS cm^?1). Here we investigate the accuracy of their estimates of the amounts of gypsum dissolved in waters collected in gypsum karst terrains, expressed as total hardness (TH) in mg L^?1 of CaSO₄·2H₂O (GYP). Total dissolved solid concentrations (TDS) are also considered. Curves obtained with the program PHREEQC, for the dissolution of pure gypsum in water at 25 C, are compared with 574 comprehensive water chemical analyses selected from gypsum karst studies in Europe and the Americas. Principal common and foreign ions encountered are the BNC group (bicarbonates, nitrates, chlorides). It is found that GYP = 1·12^·SpC + 62 where BNC < 33% (Cl^? < 5%), with one standard error <5% for waters with SpC > 2400 µS cm^?1; GYP = 0·74^·SpC + 777 where BNC < 33% (5% ≤ Cl^? < 15%), with one standard error <10% for waters with SpC > 3100 µS cm^?1; GYP = 0·97^·SpC ? 209 where BNC < 33% and Cl^? ≥ 15%, with one standard error <10% for samples with SpC > 4300 µS cm^?1. There are similar results for the more complex waters found in gypsum karsts where much carbonate rock or salt is also present, to the limit of BNC < 50% for what may reasonably be defined as ‘gypsum waters’. Values of R² for linear correlations of different subsets of the water samples range from 0·69 to 0·96, the majority being >0·8. Copyright © 2006 John Wiley & Sons, Ltd.     

Influence of arsenic-bearing gold deposits on water quality in Zloty Stok mining area (SW Poland)

 The Sudety Mountains contain polymetallic deposits which have been exploited since the Middle Ages. Distinct concentrations of As, Hg, F, Cr in surface water near Zloty Stok suggested that groundwater in the area could also contain elevated metal concentrations. Water samples from 15 locations including Zloty Stream, mine adit discharges, and selected springs generally show low levels of dissolved components and near-neutral pH. However, arsenic concentrations range from 0.99 mg/l to 26.16 mg/l at all 15 sample locations. Mercury concentrations were locally as high as 0.011 mg/l. These high arsenic and mercury concentrations significantly exceed water quality standards and raise concerns for using Zloty Stream for potable water. Recieved: 21 December 1998 · Accepted: 8 June 1999     

Pleistocene sandur rhythms,cycles and megacycles: Interpretation of depositional scenarios and palaeoenvironmental conditions

The Drawa sandur, which is the largest, coarse‐grained sandur in Poland, dates from the Pomeranian phase of the Weichselian glaciation (c. 16 ka BP). Using Markov chain analysis we infer that five cycles and five rhythms occur in its proximal part. The cycles dominated by Gt and St lithofacies in the lower part of the sandur succession and by a GDm lithofacies in the upper part, are fining‐upward cycles deposited in braided channels during large ablation floods. Three groups of cycles are distinguished based on their genesis: (i) cycles due to channel‐sheet evolution during large floods; (ii) cycles due to braid‐bar development during initial and advanced diminishing of floods; and (iii) cycles developed in the thalweg or interbar channels. The succession as a whole forms a large‐scale coarsening‐up megacycle (‘sandur megacycle’) which corresponds to a phase of ice‐sheet advance. Because the cyclicity was evident from Markov chain analysis of the sedimentary succession, we suggest that this statistical tool is valuable for reconstruction of glacifluvial sedimentary conditions, particularly as it can shed new light on the palaeogeographical development of sandar.