A stress-strain state analysis of the road transport works foundations on seasonally freezing soils

This article discusses the road transport works foundations when they are located in the seasonally freezing soils zone. Some culvert aqueduct utilized structures were considered and analyzed as an example, in the scope of most common structures on the road network and that also has an insignificant weight. Some constructive solutions disadvantages of these pipes were pointed out. It is noted that the operational characteristics of nonfrost-susceptible soil decrease in the watercourse filtering process and settling small particles and reported the dependence of the relative soil frost boil on the fine aggregate percentage. As an example of the frost boil forces influence, a typical culvert aqueduct design is considered. The calculation of axial and tangential heaving forces that affect the crown of tube is performed, assuming that the bedding soil is contaminated. Based on the calculation, rise calculated value dependence graphs of the unstressed base on the soil dampness and the heaving soil thickness, and the heaving pressure on the soil dampness are presented here. Due to the insufficient value of the forces holding back against lifting, possible negative consequences of the frost boil impact forces are presented, this affects not only the culvert aqueduct operational characteristics but also the roadbed smoothness and traffic safety. Thus, the need for additional measures to prevent soil swelling under the pipe head is justified. Recommended measures to prevent excessive deformations during frost boil, as well as modern aspects of the development of such technologies, are considered. Conclusions are made about their applicability and feasibility in relation to small artificial structures of transport infrastructure.

The bridge piers sagging problem under permafrost subbase degradation conditions and the possible solution

Permafrost soils are common for extensive areas of our country and when building engineering structures in such conditions, it is necessary to take into account the factor supporting subbase on the permafrost soil, which may initially have high stress-related characteristics. But the permafrost degradation phenomenon with frost retreat no less common. It can be happening both for natural reasons due to global warming, and for man-made reasons, when interference during construction and further the structure itself initiates subsoil frost retreat. For the most part, permafrost soils lose their strength and elastic properties during the frost retreat, turning into an almost liquid consistency, which entails the failure of the supports in the bearing capability and position stability. With the road network development and the bridge’s construction in the northern regions at the end of the 60s — early 70s of the XX century, the first principle of the design was widely applied. It was for use and maintenance of the subsoil in a frozen state, which means not require a deep foundation required. However, after 20 — 30 years of operation, cases of unexpected and significant bridge piers sagging began to be noted, as it turned out, was the result of permafrost soils frost retreat to the entire depth of the foundation. It was also noted that in some cases the bridge piers sagging is preceded by its frost boil phenomena, which appear shortly before piers sinking and almost complete failure. In this article case of an unexpected bridge piers failure examined on a specific bridge. After 30 years of proper functioning, pierces received such significant sagging, so in just three years that got to the point when it’s not only traffic safety but the cohesiveness of the entire structure. And before that, a frost boil was noted at some of the bridge pierce. The purpose of this study is to analyze the frost boil mechanism and sagging of the bridge pierce’ foundations due to the progressive permafrost degradation and to suggest restoring and maintaining ways for pierces’ operation capacity. Overall, the reasons and principles of permafrost subbase degradation were analyzed in this paper. through calculations using a specific example, significant sagging and bridge pierce bearing capability loss observations were justified and substantiated the effectiveness of the proposed in this article structural reinforcement measures.

Engineering Characteristics of Expansive Soil and its Improved Research Development

Expansive Soil is a kind of high plastic clay. Because it has Strong hydrophilic mineral composition, its engineering prosperities embodies that its shape contracts under dehydrating, Inflation and softening under the influence of water and the strength attenuates. This is very difficult to construct in the region of expansive soil. In the region of seasonal frozen, as capillary water rising height is larger; it is prone to phenomenon of frost boil or thawing settlement. It has important meaning to improve hydrophilic and physical and mechanical properties of expansive soil for Slope stability of embankment and cutting of highway engineering and reducing the cost of investment. The paper discusses the engineering properties of expansive soil in Detail; expound some main methods of improved expansive soil at home and abroad and compare and analysis the mechanism and characteristics of the corresponding methods. The paper introduces preliminary testing methods of Expansive soil performance and prospects improved in the future.