Shrinkage Characteristics of Boulder Marl as Sustainable Mineral Liner Material for Landfill Capping Systems

The soil shrinkage behavior of mineral substrates needs to be considered for engineering long-term durable mineral liners of landfill capping systems. For this purpose, a novel three-dimensional laser scanning device was coupled with (a) a mathematical-empirical model and (b) in-situ tensiometer measurements as a combined approach to simultaneously determine the shrinkage behavior of a boulder marl, installed as top and bottom liner material at the Rastorf landfill (Northern Germany). The shrinkage behavior, intensity, and geometry were determined during a drying experiment with undisturbed soil cores (100 cm 3 ) from two soil pits; the actual in-situ shrinkage was also determined in 0.2, 0.5, 0.8, and 1.0 m depth by pressure transducer tensiometer measurements during a four-year period. The volume shrinkage index was used to describe the pore size dependent shrinkage tendency and it was classified as low (4.9%) for the bottom liner. The in-situ matric potentials in the bottom liner ranged between −100 and −150 hPa, even during drier periods, thus, the previously highest observed drying range (pre-shrinkage stress) with values below −500 hPa and −1000 hPa was not exceeded. Therefore, the hydraulic stability of the bottom liner was given

Approaches to investigate the crack formation of mineral landfill liner systems

The municipal landfill in Rastorf (Schleswig-Holstein) is covered with a temporary till based capping system. Investigations of structural changes (water conductivity, pore function, shrinkage behaviour) were carried out with undisturbed soil cores and two- and three-dimensional measurement techniques. The usage of different techniques to evaluate the soil volume changes resulted in variations of the available water capacity (ver>ver+hor>3D) and the unsaturated hydraulic conductivity. In summary, a critical matric potential between -500 and -1000 hPa in conjunction with a low shrinkage tendency (Vs < 5 %) could be seen as main argument for the utilization of till as sealing substrate

Effectiveness of Grassland Vegetation on a Temporary Capped Landfill Site

We studied the effectiveness of grassland vegetation of a temporary capping system consisting of differently compacted boulder marl and its impact on the water balance components. This study presents the modelled water balances for the period between 2008 and 2015, performed with HELP 3.95 D (German edition). The model requires landfill design and weather data as well as soil physical and evapotranspiration parameters including the leaf area indices and evaporative zone depth with regard to the grassland vegetation. The modelled average annual actual evapotranspiration rates ranged between 277 and 390 mm year-1 or rather 33 and 66% of the annual precipitation (10-year average of 728 mm). The actual evapotranspiration rates are strongly influenced by the maximum leaf area indices that increased between 2008 and 2015 from 1.0 to 3.5 as well as the evaporative zone depth that also increased from 20 cm in 2008 to 50 cm in 2015. The empirical-mathematical–based HELP model is a useful option to successfully determine the water balance components of a landfill capping system under the given weather and site conditions including the development of the grassland vegetation

Anisotropy of soil water diffusivity of hillslope soil under spruce forest derived by X-ray CT and lab experiments

The idea of the study is to indicate direction-dependent differences in hydraulic conductivity, K(Se), and soil water diffusivity, D(θ), as function of the volume fraction related to the fractional capillary potential for each of the characteristic pore size classes by extended anisotropy factors. The study is exemplary focused on a BwC horizon of a Dystric Cambisol under spruce forest formed on the weathered and fractured granite bedrock in the mountainous hillslopes Uhlirska catchment (Czech Republic). Thus, undisturbed soil samples were taken in vertical (0°, y = x-axis) and horizontal (90°, z-axis) direction. The D(θ) values and especially the D(θ)-weighted anisotropy ratios showed that anisotropy increases with the volume fraction of macropores, MaP (d > 0.03 mm), with r2 between 0.89 and 0.92. The X-ray computer tomography (CT) based anisotropy ratio (ACT) is larger for the horizontal sampled soil core with 0.31 than for the vertical with 0.09. This underlines the existence of a predominantly horizontally oriented pore network and the fact that weathered bedrock strata can initiate lateral preferential flow. The study results suggest that combining the hydraulic conductivity as intensity and the capacity parameter by means of diffusivity results in an extended anisotropy ratio which unveils the role of the soil hydraulic characteristics in generation of small-scale lateral preferential flow. In future, the small-scale direction-dependent differences in the soil hydraulic capacity and intensity parameter will be used for model-based upscaling for better understanding of preferential flow at the catchment scale

Perforation of the Schneiderian membrane during sinus floor elevation: a risk factor for long-term success of dental implants?

Purpose: In cases of highly atrophic alveolar ridges, augmentation procedures became a frequent procedure to gain optimal conditions for dental implants. Especially in the maxilla sinus floor elevation procedures represent the gold standard pre-prosthetic and mainly successful procedure. The perforation of the Schneiderian is one of the most common complications. The aim of this study was to evaluate whether the intraoperative perforation of the Schneiderian membrane has an impact on long-term implant success. Methods: Thirty-four patients from a former study collective of the years 2005 and 2006 with a total of 41 perforations were invited for a follow-up examination to determine the long-term success rates after sinus floor elevation and subsequent implantation. Results: Twenty-one patients with 25 perforations were subsequently re-evaluated. One implant was lost due to a of periimplant infection after 232 days, resulting in an implant survival rate of 98% within a mean follow-up period of 8.9 years (± 1.5 years). Conclusion: Regarding the long-term success, there was no increased risk for implant failure or other persisting complications, e.g., sinusitis, after intraoperative perforation during sinus floor elevation in this study

a follow-up on bone graft stability and implant success

Background Until now, sinus floor elevation represents the gold standard procedure in the atrophic maxilla in order to facilitate dental implant insertion. Although the procedure remains highly predictive, the perforation of the Schneiderian membrane might compromise the stability of the augmented bone and implant success due to chronic sinus infection. The aim of this retrospective cohort study was to show that a membrane tear, if detected and surgically properly addressed, has no influence on the survival of dental implants and bone resorption in the augmented area. Methods Thirty-one patients with 39 perforations could be included in this evaluation, and a control group of 32 patients with 40 sinus lift procedures without complications were compared regarding the radiographically determined development of bone level, peri-implant infection, and implant loss. Results Implant survival was 98.9% in the perforation group over an observation period of 2.7 (± 2.03) years compared to 100% in the control group after 1.8 (± 1.57) years. The residual bone level was significantly lower in the perforation group (p = 0.05) but showed no difference direct postoperatively (p = 0.7851) or in the follow-up assessment (p = 0.2338). Bone resorption remained not different between both groups (p = 0.945). A two-stage procedure was more frequent in the perforation group (p = 0.0003) as well as peri-implantitis (p = 0.0004). Conclusions Within the limits of our study, the perforation of the Schneiderian membrane did not have a negative impact on long-term graft stability or the overall implant survival

Langzeitwirksamkeit einer temporären Oberflächenabdeckung

Der vorgestellte Ansatz zur Deponieüberwachung ermöglicht eine umfassende Funktionsüberprüfung der Rekultivierungsschicht und der mineralischen Dichtung des Oberflächensicherungssystems auf der Deponie Rastorf im Labor- und Feldmaßstab. Das Schrumpfungsverhalten der mineralischen Dichtungskomponente zeigt, dass diese im Hinblick auf den Matrixpotenzialverlauf bisher nicht von einer kritischen Schrumpfrissbildung betroffen ist und jedwede Wiederbewässerungsmaßnahmen zum jetzigen Zeitpunkt nicht erforderlich sind

Land use and soil development in Southern chile: Effects on physical properties

Different physical properties of volcanic ash soils were investigated along a transect of 120 km from the western slope of the Central Cordilleras (40°20’S, 72°06’W) to the eastern slope of the Costal Cordillera (39°39’S, 73°11’W) in southern Chile with respect to the degree of soil development (Arenosol versus Andosol stage; Arenosol: young volcanic ash soil, free of clay, tephric properties, Andosol: older volcanic soil, clayey). The Andosols show a higher total pore volume and a higher field capacity, especially due to an increase in fine pores, than the Arenosols. Furthermore, the precompression stress (Pc) as a parameter for the mechanical soil strength is higher for Andosols despite of a lower bulk density. A land use (cropland, meadow, forest) dependent variation of the investigated parameters was less distinct for Andosols. A reduction of macropores and saturated hydraulic conductivity (ks) due to agriculture could be determined in the field, but in general the values are still on a high level with ks-values >100 cm d-1. However, at higher stresses using an oedometer test the ks-values of the Andosols are highly negatively affected with values <10 cm d-1. Aggregation is of major importance for soil stability of Andosols, whereas a homogenization of soil structure will lead to a distinct decrease of Pc of approx. 50%.DFG/HO 911/45-1DFG/BA 1359/12-

Wasserhaushalt und boden-physikalische Eigenschaften einer Siedlungsabfalldeponie in Schleswig-Holstein- Das Beispiel Rastorf

Durch Vergleich der Matrixpotenziale mit dem Schrumpfungsverhalten konnte gezeigt werden, dass in der temporären Abdeckung der Deponie Rastorf bisher keine kritische Rissbildung in der mineralischen Dichtung eingesetzt hat. Zu deren Verhinderung war bisher noch keine externe Wiederbefeuchtung erforderlich. Mit dem vorgestellten Monitoring-System kann die Funktions-fähigkeit einzelner Abdeckungs-komponenten dauerhaft unter in situ Bedingungen überwacht und bewertet werden

Does Pulsed Magnetic Field Therapy Influence Nerve Regeneration in the Median Nerve Model of the Rat?

The aim of this study was to evaluate the impact of pulsed magnetic field therapy on peripheral nerve regeneration after median nerve injury and primary coaptation in the rat. Both median nerves were surgically exposed and denervated in 24 female Wistar rats. A microsurgical coaptation was performed on the right side, whereas on the left side a spontaneous healing was prevented. The study group underwent a daily pulsed magnetic field therapy; the other group served as a control group. The grasping force was recorded 2 weeks after the surgical intervention for a period of 12 weeks. The right median nerve was excised and histologically examined. The histomorphometric data and the functional assessments were analyzed by t-test statistics and one-way ANOVA. One-way ANOVA indicated a statistically significant influence of group affiliation and grasping force (P=0.0078). Grasping strength was higher on a significant level in the experimental group compared to the control group permanently from the 9th week to the end of the study. T-test statistics revealed a significantly higher weight of the flexor digitorum sublimis muscle (P=0.0385) in the experimental group. The histological evaluation did not reveal any statistically significant differences concerning the histomorphometric parameters. Our results suggest that the pulsed magnetic field therapy has a positive influence on the functional aspects of neural regeneration. More studies are needed to precisely evaluate and optimize the intensity and duration of the application