


Vol 53, No 2 (2016)
- Year: 2016
- Articles: 12
- URL: https://journal-vniispk.ru/0038-0741/issue/view/15187
Soil Mechanics



Laws of Shear Interaction at Contact Surfaces Between Solid Bodies and Soil
Abstract
Nonlinear relations based on Winkler-like and Coulomb laws are proposed to describe the process of shear interaction between structures and soil. Their advantages and shortcomings are illustrated, along with the suitability of experimental results.



Verification of the Results of Numerical and Analytical Estimates of the Settling of a Single Pile in Argillite-Like Clay
Abstract
A comparison is made of estimated settling values for a single pile, obtained using numerical (using the PLAXIS 2D software package) and analytical methods per SP 24.13330.2011, as well as with the results of field experiments.



Collapse Characteristics of High-Density Silt Under Principal Stress Rotation
Abstract
To study the collapse characteristics of high-density silt under complex loads, three series of hollow-cylinder tests were conducted on high-density saturated silt samples taken from the sea entrance of the Yangtze River. In the first series of tests, samples with high density were isotropically consolidated and then sheared under undrained triaxial loads. In subsequent tests, samples with low and high densities were isotropically consolidated and then cyclically sheared by principal stress rotation of 0-180°. Collapse and liquefaction were clearly observed in all the samples tested under cyclic principal stress rotation when the pore water pressure was equal to the initial effective confining pressure. Two critical points, the graded phase transformation point and the cataclysmic phase transformation point (collapse point), were observed for the high-density samples before liquefaction; these divided the buildup of the pore water pressure into three or two stages depending the shear stress level. At low shear stresses, the characteristics of the transformation points were hardly influenced by load frequency. The isotropic consolidated high-density silt and low-density silt expressed similar behaviors. However, in the high-density silt, the strain development could be divided into two stages by the collapse point, which corresponds to the cataclysmic phase transformation point of the pore water pressure representing the state of structure collapse. The deviator strains were limited within a narrow range of 0.2-0.4% at the collapse state. The stress state of collapse can be normalized by the quasi-unstable line in the p'-q space. Finally, we introduce the modified Seed model to successfully estimate the development of pore water pressure in high-density silt.



Experimental Investigations
Comparison of Test Results for Uniaxial Compression of Frozen Soil in Response to Constant Load and to Incremental Loading
Abstract
The feasibility is studied of estimating long-term strength of frozen soil from the results of uniaxial compression tests on frozen soil. Processing of test results for a constant load and for incremental loading permitted the determination of transition factors for longterm strength of frozen soil.



Development of Correlation Between Standard Penetration Test and Pressuremeter Test for Clayey Sand and Sandy Soil
Abstract
The standard penetration test (SPT) and Menard’s pressuremeter test (PMT) are among the available in-situ techniques. This research has been carried out with the aim to develop correlations among the in-situ parameters obtained by both methods.



Influence of Subjectivity in Determining Plasticity Parameters in Clay Soil on the Calculated Settlement of a Structure Bed
Abstract
The influence of subjectivity in determining plasticity parameters for overconsolidated clay soil on the settlement of structure beds is estimated. An elastic-plastic model of soil with isotropic hardening (PLAXIS Hardening Soil) was used to calculate settlement. It was shown that subjectivity in determining the plasticity may result in a bed settlement value that is different by 10.5%-22.0%



Analytical Prediction for Piles Used for Slope Stabilization
Abstract
Many unstable slopes are extensively supported by stabilizing piles. Excavation work, rainfall, and earthquakes can cause lateral soil movement, creating forces that act on the stabilizing piles. We present a new simplified method based on the Winkler elastic model for analyzing the response of flexible piles subjected to lateral soil movement in landslides. The new method can analyze cases in which the movement depth profile of the sliding layer is arbitrary by using a two-stage analysis method. First, the free-field soil movement data of the unstable soil mass are fitted by a polynomial spline using the leastsquares method. Then a system of differential equations for flexible piles subjected to lateral soil movement is presented to describe the behavior of the piles embedded in the slope. The formulation considers the soil-pile interaction to derive the analytical solution via a matrix pattern. Finally, the proposed method is verified by comparing the calculated results with those of three published case studies. The results show a good correlation between the calculated and measured responses of flexible stabilizing piles, verifying the reliability of the proposed analytical solution.



Design
Determining the Strength Characteristics of Concrete in Drilled Piles from Tests on Extracted Core Specimens
Abstract
A method is proposed for determining the "actual class" of concrete that is compliant with the requirements set forth in current regulatory documents and considers special aspects of the operation of drilled pile structures and the techniques for their installation. The method estimates strength variability, and in particular, for a large number of tests. Concrete class is determined from the results of destructive tests performed on specimens taken from a pile body. An approach is described that may be implemented during quality control of pile concrete that takes place at the construction site.



Compression Ratio Design and Research on Lower Coal Seams in Solid Backfilling Mining Under Urban Areas
Abstract
Large coal resources occur under buildings in the Iron Third District of Tangshan Mine, which not only greatly reduces the service life of the coal mine, but also wastes the coal resources. To ensure the safety of ground buildings and maximize exploitation of the coal resources, solid backfill mining technology is proposed. This paper studies the compression ratio of the coal seam during backfill mining with a global numerical model based on the finite difference software, FLAC3D. The compression ratio of the coal seam was also similarly studied based on theoretical analysis and the local model.



Construction on Permafrost
Using the Cooling Capacity of Liquefied Natural Gas to Freeze Saline Soil that Contains Cryopegs
Abstract
The effectiveness is considered of using the cooling capacity of liquefied gas to improve the operating reliability of cryopeg-containing saline soil infrastructure beds at gas-condensate fields. Mathematical modeling results are presented for a temperature field in soil beds in a four-layer soil massif (man-made embankment-frozen soil-saline thawed soil containing a cryopeg lens) when it interacts with a low-temperature thermal stabilizer. The rate of soil freezing was estimated for various coolant medium temperature, along with the efficiency of this method of thermal stabilization.



Some Recommendations for Ensuring the Stability of Pile Substructures for Above-Ground Routing of the Zapolyarnoe-Purpe Petroleum Pipeline
Abstract
The causes are examined for the reduction in bearing capacity and the increase in failure rate of pile foundations in permafrost soil north of the Arctic Circle. Methods of increasing or stabilizing the bearing capacity of pile supports using pile structural solutions and heat stabilizers having diverse action mechanisms.


