The article discusses the interaction of concrete structures with the soil, made on the basis of laboratory tests and numerical simulation. The objectives of the study were to obtain the strength characteristics at the contact of two different materials, to compare the obtained value of the strength reduction factor with the standard values, and also to determine the extent to which the interface must be taken into account when conducting numerical geotechnical calculations. The study was carried out using a direct shear test device, where the strength reduction factor was obtained, which characterizes the conditions of interaction between different materials at their contact. According to the results of numerical simulation, one can see how the consideration of the given characteristics of the material of the contact element affects the internal forces arising in the underground structure and its displacements. The test results showed that the particle diameter has a different effect on shear strength at the same level of normal stress. On the basis of the results obtained, conclusions were drawn on what needs to be paid more attention to when conducting laboratory tests, how strongly the consideration of contact elements with the correct set of properties affects the internal forces of the underground structure. Also, the remaining problems and factors not considered in this study determined the prospects for further research on the topic under consideration.
Introduction. Redundant strain arises in buildings and structures in areas of construction work influence caused by the deep bore tunneling performed by tunnel boring machines. The strain analysis must include an excess excavation ratio that depends on the structural features of the shield, the technology of grouting mixture injection outside the lining, the counterweight pressure applied to the shield face and geotechnical conditions so that excessive settlement could be taken account of. The purpose of the article is to identify actual values of the excess excavation ratio to raise excavation and determine the values of standard averaged excess excavation to be further applied in design. Materials and methods. This paper focuses on tunnel driving between “Stakhanovskaya Street” and “Nizhegorodskaya Street” stations. The project excess excavation ratio was applied pursuant to the regulatory documents in order to perform the analysis using PLAXIS 2D and PLAXIS 3D software packages. The method of sequential iteration was applied to identify the value of excess excavation in line with the actual settlement of buildings and structures obtained by means of monitoring. Results. The analysis has shown that the actual excess excavation ratio varies between 0.1 and 1.2 % for this construction site which is below the values required by the regulatory documents. As for the 3D setting, the values of actual excess excavation ratios are 2 to 4 times higher than those obtained for the 2D setting, although the value of the actual building settlement remains the same. Conclusions. Since the actual building settlement is smaller than the projected one, the cost of deep bored tunneling can be reduced by cutting the cost of protection of nearby buildings and structures within the area of tunneling influence without violating any safety requirements and also by reducing the number of buildings withing the projected area of influence, and respectively, by reducing the cost of geodetic monitoring over their displacements.
Rasskazov L.N., Bestuzheva A.S., Sainov M.P., CHernysh A.S., Francesco Castelli and many others were engaged in studies of the stability of slopes under seismic impact. The paper considers numerical methods for assessing the seismic stability of embankment dams in a flat and three-dimensional problems in two ways: a direct dynamic method and a pseudo-static method. Several simulation cases are considered in a flat problem on a test problem using soil properties taken from a real site of an operating hydroelectric power plant. During the simulation, the following main simulation cases were considered: the natural stability; calculation without static components; calculation with static components; impact of free vibrations; calculation with full accelerogram; calculation with static deformation properties of soils; calculation with dynamic deformation properties of soils; calculation with undrained strength of soils; pseudostatic method. The analysis of the results showed that the calculation of the seismic stability of an embankment dam by the direct dynamic method gives the results that are closest to reality, in contrast to the pseudo-static calculation method.
Introduction: During constructing tunnels by trenchless method using the shield driving method soil surface subsides. Buildings and structures which fall into the zone of influence of new construction receive additional settlements. To determine it in the calculations it is necessary to take into account the excess excavation ratio. The purpose of the study is to determine the excess excavation ratio for increasing the sample and determining the normative values of the ratio for application in design. Materials and methods: in the article there is examines the construction of a tunnel in the city of Moscow. Calculations are carried out using the PLAXIS software package in two-dimensional and three-dimensional formulations. In the calculations the normative excess excavation ratio was included and a backward calculation was also carried out in order to determine the actual excess excavation ratio according to the data of geodesic monitoring. Results: the results showed that the excess excavation ratio varies from 0.1% to 1.2%. It is much less than the values that are included in the project according to the regulatory documentation. Conclusions: due to the fact settlement is less than the calculation settlement, the cost of building tunnels can be reduced by reducing the cost of protective measures for buildings and structures, as well as reducing the number of buildings that can receive excess settlement.
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