A coupled dynamic leakage loss and flood routing model for ephemeral rivers with complex sections

Ephemeral rivers commonly occur in regions with a shortage of water resources, and their channel configuration tends to change substantially owing to cultivation, tree planting and sand extraction. There is an urgent need to restore degraded river ecosystems. During short-term water conveyance, water storage in sand pits and leakage in dry riverbeds retards the flow of water, which is detrimental for ecological restoration of the riparian zone. A coupled dynamic leakage loss and flood routing model was established to predict the flow processes in the complex river channel of the Yongding River in China. The model mainly included three sub-models of flow dynamics, dynamic leakage loss, and water balance along multiple cross sections of the river channel. The complex section is reflected in the different infiltration properties for each section, and the existence of sand pits. The water head was dominated by flow velocity and the overflow from sand pits. Owing to the difference in landforms and the deposited sediment size of the riverbed bottom, the river channel was divided into 11 cross sections and a sand pit to ascertain the respective infiltration or leakage loss processes. The input parameters of the model came from field surveys of sand pits, river geometry and hydrogeology. The model was also calibrated and validated using monitoring data from ecological water releases into the Yongding River in 2019 and 2020. This coupled model can predict the water leakage loss and flow process of the water head and also provide important guidance for river reconstruction and ecological restoration.

Agromeliorative methods of biological reclamation of sand pits in the conditions of Far North

The most important method of biological reclamation of sand pits is the introduction of peat as a cultural layer. To reduce soil acidity during reclamation, lime fertilizers must be applied.

Рhysical simulation of erosion of bottom pits

The present paper is devoted to research of the erosion of large-scale sand pits in the water flow. The investigations were performed in the hydrodynamic flume with sandy bottom. To provide suitable conditions for sediment transport in the flume, the analysis of the factors leading to the motion of sediments was carried out in accordance with the Shields diagram. It was shown that the flow regime created in the laboratory channel promotes the development of natural bed forms such as ripples. Estimations of the velocity of movement of the ripples were obtained. The experiments with large sand pits on the flume bottom demonstrated that those disturb the balance of sediments and cause the reformatting of the water flow. To assess the influence of the pit configuration on the erosion process, two-dimensional triangular and trapezoidal pits were considered. It was found that the longitudinal profile of the triangular pit changes due to sediment deposition on its upper slope and erosion of the lower slope. The pit upper slope levels out and shifts forward due to the continuous flow of sediment in this region. The depth of the unevenness also decreases owing to deposition of the sediment directly on its bottom. Due to the blow of water jet to the pit lower slope, the zone of maximum erosion of the bottom surface is observed here. The bottom reformatting leads to the displacement of the pit downstream. Studies of the erosion of the trapezoidal pit have shown that its upper slope is first shifted toward the lower slope until the trapezoidal profile turns into a triangular one. The pit erosion causes also the deformation of natural forms of the channel bed and destabilization of sediment discharge. The analysis of the obtained data demonstrated that the reformation of channel bed is a durable process depending of the ratio of pit scales to the volume of sediment. The present study is useful for development of engineering solutions directed to reduction of risks caused by the interaction of sand quarries with hydraulic structures in rivers.

Do Diversity and Bio-morphological Spectrum of Psammophytes Matter in Restoring Vegetation of Sand Pits?

Open mining of sand is executed in the sand pits. After completion of the work sand pits are usually recultivated: firstly they are graded and then planted with trees and shrubs, but very often sand pits are abandoned to regenerate themselves. The sand pit becomes a source of dust and a hardly healed wound on the earth’s body. In order to provide an adequate revegetation on such substrates, it is necessary to study biomorphological peculiarities of growing plants in a very specific environment characterized by high stiffness of slopes and high mobility of the substrate. The material for our study collected from Moscow Region sand pits in the Russian federation. Plants were collected from both northern and southern exposure slopes. Our work is based on the geobotanical descriptions made according to standard method on experimental sites of 5x5 m2. The results of the undertaken shows that Compositae, Gramineae, Fabaceae are the most representative of the surveyed one hundred twenty seven species of higher vascular plants from 29 families. Diversity on the southern slopes was more than on the northern ones. Species diversity is determined by the successions occurring spontaneously after a rough anthropogenic intervention, under the influence of such environmental factors as lighting, moisture, texture and richness of soil. The spectrum of life forms showed that the overwhelming majority according to K. Raunkiru are hemicryptophytes. Perennial herbaceous polycarpics are dominant in the spectrum of life forms, according to I.G. Serebryakov.

Shield Equipment Optimization and Construction Control Technology in Water-Rich and Sandy Cobble Stratum: A Case Study of the First Yellow River Metro Tunnel Undercrossing

The Lanzhou Yellow River Tunnel is the first metro shield tunnel that undercrosses the Yellow River in China. It was completed after successfully overcoming several construction challenges, including strata with a high proportion of large-sized sandy cobble stratum being saturated, large-scale sand pits along the bank of the Yellow River, and a combination of boulders and erratic blocks of rock. Given the difficulties in constructing the tunnel, this paper summarizes the scheme employed to transform the cutter and cutter head design to be applicable to sandy cobble stratum and the key technology used to form the slurry film to facilitate crossing the sand pits in a systematic way. The transformation scheme primarily involved the addition of an adjusting device to control the aperture ratio of the shield on the cutter head, a protective device for the hob hub, and a protective device for the piston rod in the oil cylinder of the crusher. The implementation of measures mentioned above guarantees the safe completion of the tunnel, which can provide a reference for similar projects.

Nowe stanowisko Lycopodiella inundata (Lycopodiaceae) w Kotlinie Biskupiego Boru (Wyżyna Śląska)

Lycopodiella inundata is a rare and protected pteridophyte species in Poland. It usually occurs in oligotrophic wetlands, mainly in transitional moors (Rhynchosporetum albae). Lycopodiella inundata has rarely been found at natural sites recently, probably due to unfavorable environmental changes, but appears more and more often at sites created by human activity, such as sand pits, gravel pits and the banks of fish ponds. In 2014 a new site of L. inundata was found in the eastern part of the Szczakowa sand pit (19°25′35″E, 50°15′18″N). In this area, L. inundata grows well and occurs abundantly in small conspecific patches, aggregations, or as solitary plants. The main threats to this site are expansion of forest and shrub vegetation, reed expansion, changes in groundwater level, and drainage of the area.

Assessment of professional hazards at the position of the backhoe loader

The job of a backhoe operator is to perform earthworks as well as auxiliary, transport and order work. The working environment of the backhoe loader operator are construction sites, gravel pits, sand pits, quarries, and mines. The backhoe operator works both inside and outside the cab and is exposed to the presence of many environmental factors that can cause accidents at work and occupational diseases. The paper presents in a synthetic way the characteristics of the profession of a backhoe loader operator paying attention to such aspects as: the scope of performed activities (tasks), working environment and qualifications and qualifications necessary to perform this profession. Then, a review of occupational hazards occurring at the workplace of a backhoe loader operator was made. Supplementing the above considerations are the results of the occupational risk assessment carried out using the Risc Score method. As a result, the authors of the publication present examples of corrective actions to minimize the level of occupational risk.