Mechanism specifics of the landslide-hazardous massif limit state formation and landslide block displacement

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Abstract

In the landslide cycle of deep block movement development, the landslide process starts with the separation of the new landslide block from the bedrock massif, and it ends with the block displacement until the steady landslide head is formed in the hotbed (on the landslide slope). The initial stressed state in the bedrock massif with horizontal earth surface (before the landslide block forms) is controlled by the Mohr-Coulomb criterion. The landslide hotbed forming as well as the sliding basis appearing cause the change in the initial stress state and the formation of horizontally oriented dissipative blocks-structures. The principal stresses are concentrated on the boundary surfaces of these structures (which are of a circular cylindrical shape). The limit state forms along these boundary surfaces of the appropriate block in the local massif zone on the contact with the landslide hotbed. The displacement occurs along the same surfaces, provided the equilibrium is disturbed. In forming the limit state of the head scarp massif, the adjacent part of the landslide massif (within the boundaries of the earlier separated landslide block) acts as an additional load (creates an active vertical pressure from the landslide mass weight) to the horizon of the landslide basis. The bedrock massif interacts with the slope at the stage of preparing block displacement. The block limit state is achieved in case the head scarp height reaches its critical value (the slope edge is higher than the landslide head). Under the soil masses weight in the new landslide block, separated from the bedrock massif, as it subsides, the soil crushes in a lower part of the block, which has lost its balance, in the slide basis zone. The paper considers the conditions of the new landslide block formation, the beginning of block displacement process, the mechanism of interaction between blocks, the bedrock massif and the landslide body, which consists of earlier displaced landslide blocks. The paper also provides the rationale for the soil strength changes in the process of displacement and its significance in the landslide cycle completing, with comparing the results of theoretical and experimental studies.

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About the authors

G. P. Postoev

Sergeev Institute of Environmental Geoscience, Russian Academy of Sciences

Author for correspondence.
Email: opolzen@geoenv.ru
Russian Federation, 13, str. 2, Ulanskii per., Moscow, 101000

References

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Supplementary files

Supplementary Files
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1. JATS XML
2. Fig. 1. Schematic section of the landslide slope at the final stage of the landslide cycle of development of a deep block landslide compression-extrusion: 1 - the main massif; 2 - landslide massif; 3 - sliding surface; 4 - crack of stabbing a new landslide block (the beginning of a new landslide cycle); Apl, Acr, Asl - the levels of the plateau, landslide terrace and sliding surface (slip basis).

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3. Fig. 2. Schematic section of the landslide slope with the outline of the block-dissipative structures in the soil massif: 1 - the main massif; 2 - landslide massif; 3 - the boundaries of the block-dissipative structures; Apl, Acr, Asl - levels of the plateau, landslide terrace and sliding surface.

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4. Fig. 3. Scheme for the derivation of the equation of the limiting equilibrium of a landslide-hazardous massif of the supra-creeping ledge during the formation of a new landslide block: 1 — a radical massif; 2 - landslide massif; 3 - displaced landslide block with a day surface at the level of the landslide terrace at the end of the landslide cycle; 4 - block I in the massif of the above-creeping ledge of the primary massif according to contact with the landslide terrace.

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5. Fig. 4. Scheme for calculating the stability of the indigenous massif in the zone of the formation of a new landslide block: 1 - landslide-dangerous indigenous soil massif (zone "a"); 2 - landslide body of displaced soils (zone "p"); 3 - the considered deformable soil horizon (at the level of the sliding surface of the landslide) with the characteristics φ, с and σstr; σ1а and σ1р - values of household pressure, respectively, in the main body and landslide body at the stall wall; Hcr - the critical value of the height of the wall of failure, determined by (1).

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6. Fig. 5. The average resistance to shear on the sliding surface of landslides in clay soils, according to A.E. Turovsky [15]: 1 - graph of residual strength according to laboratory tests Sost = 9 + 0.14σ; 2 is a graph of the residual strength according to the inverse calculations for natural landslides Sе, OT = 4 + 0.07σ; landslides: 3 - in plastic clays; 4 - in hard clays; 5 - in semi-rock formations.

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