Numerical Study on the Behavior of Square Stiffened Caissons Penetrating into Normally Consolidated Clay

Significant difference between predicted and measured installation resistance of stiffened suction caissons was identified due to the existing uncertainty regarding the mobilized soil flow mechanisms. This paper describes an extensive investigation of square stiffened caisson penetration in nonhomogeneous clays undertaken through large deformation FE (LDFE) analysis to identify the soil flow mechanisms around and between lateral ring stiffeners. A detailed parametric study has been carried out, exploring a range of nondimensional parameters related to stiffened caisson geometry, caisson roughness, and soil strength. The LDFE results were compared with centrifuge test data in terms of soil flow mechanisms, with good agreement obtained. Two interesting features of soil flow inside the caisson were observed including soil backflow into the gaps between the embedded stiffeners and soil heaving at the surface. It shows that the cavity depth can reach ∼5 m. Finally, simple expressions were proposed for estimating the critical depths of soil backflow and cavity formation.

Stability Analysis of Soil Flow Protector and Design Method for Estimating Optimal Length

Underground cavities can develop below structures, leading to ground settlement and hindering the development of urban infrastructure. Soil flow protectors (SFPs) have been developed to prevent and alleviate problems due to the formation of such cavities. In this study, we performed scaled model experiments to develop a design method for an SFP with an adequate safety factor under different installation lengths of its upper and lower parts in sandy ground. The installation of the SFP reduced the average surface settlement ratio to the range of 0.44–0.72, thus demonstrating its effectiveness in reducing ground settlement. In addition, we proposed a relational equation for determining the optimal length ratio of the SFP and the settlement ratio. An analysis of the influencing factors showed that the lower part of the SFP influenced the settlement reduction, whereas the upper part influenced the stability of the SFP depending on the ground settlement ratio. Finally, we have proposed an optimal length equation for the SFP and presented a flowchart for the design method. The results of this study can serve as a design basis for the efficient construction of infrastructure.

Unidirectional consolidation of clay soils and flocculated suspensions

A model of the unidirectional consolidation of a clay soil or flocculated suspension between a series of parallel drains is developed. A convective-diffusion equation for the pore pressure is derived, and an equal-strain approximation leads to an expression for the average effective stress profile between the drains. The solution depends on a Peclet number quantifying the ratio of the bulk soil flow rate to the rate of consolidation. By adjusting the number, height and spacing of the drains, very high rates of dewatering can be achieved. A potential application of the method to the rapid dewatering of mine tailings is described.

Experimental Study on Response Law and Failure Process of Slopes in Fully Weathered Granites Under Precipitation Infiltration

To investigate the response law and failure process of slopes in fully weathered granites under precipitation infiltration, a typical fully weathered granite slope is selected for sampling in Fengkai, Guangdong. The physical simulation experimental study of rainfall-induced landslide is conducted, in which Weber criterion is used as the similarity criterion for precipitation. The research results reveal that under precipitation infiltration, the fully weathered granite slope responds quickly. Further, the water content increases sharply, and the matrix suction quickly dissipates. After dissipation, the matrix suction transforms into pore water pressure, which accelerates the deformation of the slope. The wet peak has a large infiltration depth in the slope, and the acceleration of deep part is lower than that of the shallow part. Under the action of precipitation, the fully weathered granite model undergoes four stages of failure. Firstly, gullies and cracks appear. Secondly, cracks propagate and link up. Then, the soil on the slope surface swells and ruptures. Finally, the slope slides locally until the entire slope creeps, collapses, and transforms into a "soil flow." Based on the analysis of precipitation similarity, the landslide will be triggered in fully weathered granite slope by precipitation when the precipitation intensity comes up to 155 mm/d, and the landslide occurs at an accumulated precipitation of 304 mm. Overall, the results can provide a reliable theoretical basis and abundant experimental data for the prevention, monitoring, and forecasting of geological disasters in granitic areas.

WAYS TO INCREASE THE PRODUCTIVITY IN CONTINUOUSLY OPERATING TRENCHING EXCAVATORS

The article considers and reasons the ways and possibilities to create the highly efficient constructions of trenching excavators that dig trenches of the defined profile by means of using bucketless rotors as soil excavating implements together with design of the discharge assembly improved construction. Study objective: to create a bucketless highly efficient rotary implement of the trenching excavator with two-stage discharge. Study object: continuously operation earthmoving machines. Research technique – analytical-experimental. One of the most important problems for the machine-building industry of Ukraine is the efficiency improvement of machines created in the country. Solving of this problem is required due to necessity to perform the increasing amount of earthworks in building and construction works. The cheapest way to perform lengthy soil excavations is to excavate them with trenching excavators. Increasing of their productivity is the one of the main directions to improve the efficiency of the earthworks mechanization. Increasing the efficiency of trenching excavators is possible by means bucketless rotary implement usage and by improving of the rotary discharge process. The study justifies and proves the scientific hypothesis about the possibility to use the force of the soil flow header pressure create by the soil that is being transported from the excavation for the bucketless rotary implements discharge. This allows by means of two-stage discharge of the implement to ensure the full clean-up and to improve the productivity of the soil excavation. The study analytically justifies the requirements for the main construction parameters of the bucketless rotor. Based on the obtained results the technical proposal is created for highly efficient construction of the bucketless rotary implement of the trenching excavator with two-stage discharge. KEYWORDS: BUCKETLESS ROTOR, SOIL, TWO-STAGE, DISCHARGE, DISCHARGE ASSEMBLY, TRENCH DIGGER

SOME QUESTIONS STUDY OF DEFLATION PROCESSES AND SAND TRANSPORT IN THE DRAINED BOTTOM OF THE ARAL SEA

The article discusses the results of the study of sandy deserts, which allowed us to obtain and reveal a number of important laws and mechanisms of formation, formation, movement and development of Aeolian landforms. The establishment of these patterns helps to solve a number of practical tasks to combat sand drifts in the sandy desert of various objects. In connection with the prospects for the development of this territory, it is very important to know the direction and intensity of the development of these processes. The obtained data on the mechanism and structure of the entire air-soil flow, starting from the moment of its formation, i.e. in the blowing zone, and ending with the transfer and deposition of soil particles by wind in the accumulation zone, make it possible to increase the level of scientific validity of the rational use of soil resources, as well as to take timely measures to protect the environment.