A comparison of PLAXIS and LANDSLIP software packages for landslide hazard assessment

Difficult soil conditions are observed on almost 90% of the territory of Ukraine. Therefore, unpredictable changes in physical and mechanical characteristics of soils due to technogenic and natural geological factors can lead to dangerous deformation processes. A lot of such processes end with soil accidents and catastrophes. Among them, the landslide soil accidents and catastrophes rank first in Ukraine and second in the world (after earthquakes) in terms of the volume of economic damage inflicted. Therefore, construction of buildings and structures on landslide areas is not recommended by Ukrainian building codes. To protect urban areas and existing structures from landslides, it is often necessary to carry out complex and sometimes very expensive engineering protection measures. Preventing landslide disasters helps to avoid casualties and is less costly than eliminating their consequences. Unfortunately, insufficient development of methods for assessing the degree of landslide hazard and reliability of anti-landslide structures leads to the fact that requirements of the building codes are not always met. Therefore, the number of landslide accidents and disasters is growing in Ukraine from year to year. It determines relevance of work to improve the methods for calculating landslide hazard and loads on anti-landslide structures, increasing reliability and efficiency of engineering protection of territories and structures. Currently, due to computerization of calculations, their labor intensity for designers is significantly reduced, which makes it possible to widely use variational methods. In Ukraine, when calculating the stability coefficients, the well-known and widely used calculation methods of Maslov – Berer and Shakhunyants are used. They are recommended for use by the modern building codes of Ukraine. The approximate computational methods of Maslov – Berer and Shakhunyants are based on application of the theory of the marginal stress state of the granular medium, like most other computational methods for assessing landslide hazard. To determine the error of these approximate methods in comparison with the more accurate numerical solution based on the Mohr – Coulomb soil model implemented in PLAXIS software package, the comparative calculations were carried out for the identical landslide sections. Two types of the soil conditions were considered: clay and sand. Therefore, we have calculated the stability coefficient for the same landslide slope using PLAXIS software package based on the Mohr – Coulomb model and using LANDSLIP software package based on the approximate methods of Maslov – Berer and Shakhunyants. The absolute error by the Maslov – Berer method was 0.21 for sand and 0.03 for clay; relative error for sand – 18.75%, for clay – 1.83%. The absolute error according to the Shakhunyants method was 0.11 for sand and 0.2 for clay; the relative error for sand was 9.82%, for clay – 12.2%.