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Loess’s permeability properties increase under alternating wet and dry conditions, a phenomenon that is closely related to the soil’s pore structure. Among the pore structure properties, spatial topology is important. To further investigate the relationship between loess’s spatial topography and its infiltration properties under alternating wet and dry conditions, loess with different water contents is scanned by an industrial computed tomography (CT) scanner, and single-phase seepage simulations are performed. The results show that the diameters of the connected pore spaces increase along with water content; the pore throat length is positively correlated with the water content, reaching a maximum of 753.32 μm; and greater water contents result in stronger pore connectivity and larger increases of connected pore space coordination numbers. The results of the permeability simulation show that increases in connected pores, pore throat lengths, and coordination numbers lead to increased permeability, and the correlation is strongest between the coordination number and permeability. It is important to study the relationship between spatial topology and loess permeability for practical engineering applications.

While research into landslide disasters is relatively extensive and in-depth, the false alarm rate is still high. Previous research has indicated similar mechanical problems between the seismic faults and the sliding interface of landslides. Here, we introduce asperity theory from seismology to improve the prediction level of landslide damage. We designed a soil landslide model sized at 2.0 m × 0.6 m × 1.5 m where the upper layer is loess and the lower layer is mudstone. Four pore water pressure sensors and four soil pressure sensors are equally spaced at the loess-mudstone interface. The monitoring results show that the sliding interface has the characteristics of asperity, while the landslide failure is a nonlinear movement process. Although it is difficult to directly measure asperities, we can infer their position at the sliding interface by measuring the velocity or displacement of the landslide surface. We install monitoring sensors at the surface region corresponding to the asperity. Once there is a large deformation in the region, there is a significant probability that the entire landslide will be destroyed. Thus, asperity theory was applied for an early warning system of landslide disasters, which will greatly improve the monitoring and prediction of future landslides.

The hazards associated with travelling on highways in desert regions arise mainly from wind-borne sand disasters, such as complete or partial burial of the road surface by sand particles, and from erosion of the roadbed by the particles. To simulate the damage process caused by sand particles on roads in the desert, scaled-down tests were performed in a wind tunnel whereby sand particles of differing diameters and roadbed models of different gradients were tested and the impact trajectories of the sand particles were captured using a high-speed camera. The results showed that the impact trajectories may be classified into four types, and the proportion of each type is essentially stable with the statistical curves for the trajectories being similar to the Poisson distribution. The diameters of the sand particles and the slopes of the roadbed model influenced the impact trajectories, which also impacted the statistical values for each particle type. Owing to the Magnus force, the direction of rotation and the angular velocity of the sand particles controlled the nature of the collision trajectories; however, the direction of rotation did not remain in a fixed plane and the rotation speed only reached about 20% of the value of the first critical speed. The wind tunnel experiments enable a better understanding of the motion trajectories, rotation speed, force situation, and collision trajectories, providing a useful benchmark for research on wind-induced disasters on roads in desert regions.

With the development of digitalization in various fields, the water conservancy field is gradually developing digital three-dimensional visualization research to promote the development of digital watershed construction. This paper deeply analyzes and discusses the theory and application of three-dimensional visualization of river water scenes and realizes an interactive visual simulation system based on virtual reality technology, which simulates simulation and operation management, which can greatly accelerate the data. The processing speed makes the huge data be effectively utilized to provide visual interaction means for numerical simulation and data analysis, improve the efficiency of numerical calculation, and realize human-computer interaction communication, so that people can observe the phenomena and laws that are difficult to observe by traditional methods. The rationality of the mathematical model is analyzed for effectiveness.

The present horizontal movement of the Ordos Block is the result of the movement interaction between the Ordos Block and the mainland of China. The main dynamic sources are the northeastern pushing by Qinghai–Tibet Block, and the northwestern extension of the northern margin of the block. The latest GPS velocity field observational evidences shows that the velocity field of Ordos Block and around has a significant change from 1999 to 2015, and the change is significant in the northeast margin, the northwest margin, the southwest margin, and the southeast margin of the block. The velocity of left lateral movement of the northsouthern margin of Ordos Block is much larger than the right lateral movement of its eastsouthern margin. By using the seismic data of Ordos Block since 1970, the analysis of strain accumulation, strain release, stress distribution, and stress field show that the northern margin of Ordos Block is the main active area not only in the block edge, but also in North China. The strain around Ordos Block has been accumulating continuously since 2000, and this is the longest period of strain accumulation since 1970. Some signs of strain relief appeared after Alashanzuoqi M s5.8 earthquake in 2015. There are some areas with extremely large strain anomalies appear in the northern margin of Ordos Block.

Straw checkerboard barrier (SCB) technology plays a predominant role in desertification control and is proven to be the most effective method currently in practice. Yet it has several minor drawbacks; for example, it cannot suppress floating sands, nor hold large amounts of water, and it cannot fix the vegetation in place to ensure it has adequate lodging resistance. In recent years, microbially induced carbonate precipitation (MICP) technology has emerged as a research hotspot in desertification control. Here, we reasoned that combining SCB and MICP technologies could enhance desertification control, thereby increasing its overall efficacy. To investigate this approach, we collected data on SCB technology from a field investigation and through a literature search, and collected data on MICP technology via literature search and by conducting laboratory and field experiments. Sixteen key factors for desertification control are summarized, and their parameters and effectiveness are analyzed in detail. Taken together, our results show that MICP technology can effectively rectify the shortcomings of SCB technology, so combining both technologies for mitigating desertification should have promising outcomes, by accelerating the process of sand fixation, vegetation restoration, and ecological restoration. The prospects of applying SCB and MICP techniques jointly for desertification control are exciting, as they are both theoretically compatible and complementary to each other.

The counterclockwise rotation of the Ordos block has a complex geodynamic background. The fracture zone around the Ordos block also has complex stress and strain fields. We propose an initiative–passive vortex structure model (I–P model) to explain the geodynamics of the Ordos block and the surrounding fracture zone. We analyze the relative velocity of the fracture zone around the Ordos block based on the GPS velocity field and use a multiple kernel function to calculate the strain field in the study area. According to the fault distribution and tectonic activity, we divide the fracture zone around the Ordos block into seven sections and use the I–P model to analyze the relative motion state and strain variation in these sections. The results show that the north and south margins of the Ordos block exhibit sinistral strike–slip movement, primarily because the eastward movement of the Ordos block is faster than the movement of the Yanshan block and slower than that of the Southern China block. The east and west margins of the Ordos block exhibit dextral strike–slip movement, mainly due to the counterclockwise rotation of the block. The NE extrusion force from the Tibetan Plateau increases the strike–slip rate of the eastern Ordos block. The I–P model perfectly explains the change in strain around the block. It also systematically explains the regional dynamic background of the area around the Ordos block. According to the I–P model and the surface strain characteristics inside the Ordos block, we find that a tensile belt runs from the southwest to the northeast. This means that the block will probably disintegrate in the future, and the length-to-width ratio of the block will be seriously unbalanced. Therefore, the Ordos block will no longer rotate counterclockwise. The I–P model agrees with the kinetic characteristics of the present vortex structure and will provide a reference for further research on the Ordos block.

We prove the existence and uniqueness of a similarity solution for an axially symmetric flow of fresh and salt groundwater with nonconstant injection rate. A singular two-point boundary value problem is also extensively studied.

In this paper, a semilinear elliptic-parabolic PDE system which arises in a two dimensional groundwater flow problem is studied. Existence and uniqueness results are established via theL p − L q a priori estimates and the inverse function theorem.

In this paper a nonlinear elliptic-parabolic system which arises in a two-dimensional groundwater flow problem is studied. Abstract results on evolution equations are employed to obtain existence and uniqueness results. Regularity and stability properties of the solution are also considered

In a recently proposed model for the injection of steam into an air-filled soil, an equation which defines an unknown coefficient in terms of the parameters in the model arises. The paper examines this equation. It is shown that the coefficient is well-defined. Furthermore, quantitative and qualitative properties of the dependence of the coefficient on the parameters in the model are derived. A crucial role in the analysis is played by the Mills ratio for the normal probability distribution. By the bye, bounds for the Mills ratio, which to the best of the authors' knowledge are new, are obtained.

The present paper addresses the unsteady process of steam stripping of the unsaturated zone of soils contaminated with volatile nonaqueous phase liquids. First, on the basis of Darcy's law and the conservation laws of mass and energy, a one-dimensional model is derived for the propagation of the steam front in the start-up phase. It is shown that this process is governed by one dimensionless group y. Subsequently, the evaporation mechanism behind, the transport to, and the condensation at the front of volatile contaminants are considered, taking the view that nonequilibrium exists between liquid and vapor phases. The model leads to a moving boundary problem which is of special mathematical interest. By a suitable transformation of the governing partial differential equations, the problem is brought into a fixed domain and solved numerically. For a broad range of the governing dimensionless numbers, computation results are presented. The results obtained in this paper make clear the role of the prevailing principal physical phenomena during the start-up phase of the process.

In this paper the unsteady process of constant pressure steam injection into an unsaturated porous medium (e.g. contaminated soil) is studied. Darcy's law, an overall mass balance and an energy balance at the steam front are applied to determine the position of the front. The solution, in closed form, reveals that the front position is proportional to ...t. Furthermore, an asymptotic analysis provides an approximate expression for the front position. This result quantifies the case of negligible conductive heat transfer.