Deformation properties of a subgrade in structures reinforced with full displacement piles

Abstract

Construction of transport infrastructure facilities on weak subgrades requires special soil improvement measures. One of the advanced methods for deep subgrade soil compaction is known to be Full Displacement Piles (FDP). The purpose of this paper is to establish dependencies of subgrade deformation properties of a soil body reinforced with full displacement piles on reinforcement parameters and soil conditions. Using numerical simulation methods, the authors identified reinforcement parameters and initial soil indicators that have a significant effect on change in the deformation modulus of the reinforced body in the considered boundary conditions. Results of field experimental studies confirmed the reliability of the newly established relationships and regularities.

Monitoring the deformation parameters of reinforced soil masses

“…The spacing of reinforcing elements, their diameters and material characteristics depend on the required deformation characteristics of the massif, which are to be achieved by reinforcement. Analyzing the authors experience in the reinforcement of soils by vertical elements [6,7] and examples of implementation of such reinforcement published by other authors [8,9,10] and recommendations of regulatory documents one can conclude that when reinforcing clay and sandy soils the reinforcement elements are usually placed in a staggered arrangement with a step of three to five diameters of reinforcement elements (Figure 1). By varying the diameter-dependent spacing of the reinforcing elements, the deformability and strength of the reinforced massif can be increased or decreased through the corresponding influence of the material of the reinforcing elements.…”

“…A reliable deformation modulus value of the reinforced massif 𝐸𝐸 𝑑𝑑𝑐𝑐𝑓𝑓𝑓𝑓𝑓𝑓 , determined from the results of the die tests, can be calculated as 𝐸𝐸 𝑑𝑑 𝑐𝑐𝑓𝑓𝑓𝑓𝑓𝑓 = 𝐾𝐾 𝑐𝑐𝑐𝑐𝑐𝑐р 𝐸𝐸 𝑑𝑑 (6) where 𝐾𝐾 𝑐𝑐𝑐𝑐𝑐𝑐р -correction factor, determined according to the formula (6); Ed -deformation modulus value of the reinforced massif obtained from a die test using a die with a proportionality factor 𝑘𝑘 𝑑𝑑𝑑𝑑 (calculated from formula (2)) ranging from 5 to 15.…”

“…These quality assessment methods therefore make it possible to determine the strength and deformation characteristics of the reinforcing elements themselves. This approach to assess the quality of reinforcement of soil masses has been investigated in works [1][2][3][4][5][6] and shows its effectiveness and relevance. However, it only allows the achievement of the required parameters for a part of the reinforced soil mass, without considering the joint operation of the reinforcing element and the surrounding soil in the massif.…”

Cementation of soils by wristband-pipe injection technology in conditions of thawing perpetually frozen soils

“…Table 1 Calculation of changes in the values of the porosity coefficient e and the yield index I L as a result of cementation Calculation algorithm was accepted to define changes in modulus of deformation after cementation of soil foundation [19,22]. The calculation shall be made for the pile at the intersection of A/1 axes, where according to results of monitoring the greatest settlements were found.…”