Soil with weak bearing capacity, like peat and organic grounds, is widespread in Latvia. Most of Latvia’s national road network are built on this type of soil. During the design of road project and during the geotechnical investigation, when sedimentary rocks of organic origin are detected, the civil engineer may encounter many different problems that can delay the project development process. The designer may have to contact the customer of the specific object and joint efforts to try to find the most advantageous, rational, economical and safest solution for road users. The simplest, but certainly not the cheapest, solution is to replace the soil layers with weak load-bearing capacity, which is very often foreseen in the projects, because civil engineers lack the experience and knowledge to offer alternative solutions. In most of Europe and other countries of the world, existing and prospective roads are geotechnically designed for areas where sedimentary rocks of similar origin and soils of weak bearing capacity are common. In order for civil engineers in Latvia to be able to perform geotechnical design, it is necessary to educate designers in the relevant field. The aim of the doctoral thesis was to develop a calculation method that, using the properties of soil layers and other materials, can determine the bearing capacity of the highway structure. In addition, it was planned to develop a transport load model, which designers will use to perform geotechnical calculations of highway structures and develop constructive solutions. When performing calculations of soil layers using finite element programs, it is very difficult to accurately estimate the bearing capacity of the existing foundation and to define the load caused by transport in the calculation model, because it is dynamic. Literature analysis, research of other studies was carried out in the work. A block diagram of highway project solutions has been developed, with the help of which the engineer can analyse the project data and determine what design steps need to be taken. As part of the doctoral work, geotechnical investigation data from several construction and design objects were obtained, and a test area was created, where various geotechnical field test investigations were duplicated at several points. All the obtained information was collected and analysed, making significant conclusions about the accuracy of the results of each study. Based on the data of the geotechnical investigation, a method was developed for modeling the bearing capacity of the highway structure. In addition, an analytical calculation formula was developed for evaluating the bearing capacity of the existing foundation. A traffic load model has been developed, which can be used for performing geotechnical calculations of highway construction and developing project solutions. The doctoral thesis consists of an introduction, five chapters of the main part of the thesis, conclusions and a list of used literature. The volume of the work – 123 pages, 78 pictures, 13 tables and 79 literature sources. The doctoral thesis is written in Latvian.