## 6 Conclusions  
Full-scale static load tests and numerical modeling of bored piles with and without a protective silicate shell of a new design in saline silty-clayey soils were performed in this study, based on which the following outcomes can be highlighted:  
1. A method for the construction of a bored pile with a protective shell cast from a silicate solution was developed. The copyright, novelty, and efficiency of the proposed technology were confirmed by a patent [34] and by the results of experimental approach. 2. The physicochemical processes of the formation of a protective shell around a bored pile was described in the process of the interaction of a silicate solution with salts present in saline soils, as a result of the crystallization of acidic silica gel films on soil particles and capillaries. 3. According to the results of static pile load (SLT) tests of ordinary piles and piles with a protective and bearing shell of the new design, the bearing capacity of the casts exceeded the bearing capacity of ordinary piles, without soil wetting, by 2.5 times on average, and after soil wetting--by 3.2 times. 4. According to the SLT results, soil wetting greatly affected the bearing capacity of ordinary piles, while piles with protective silicate shells were more stable due to the increased cross-section of the support area. It was determined that soil wetting decreased the bearing capacity of the ordinary pile by 27.7% on average, and by 8.9% in the case of a pile with protective and the load-bearing silicate shell. 5. Numerical modeling of the piles with a protective shell showed a great convergence of the results of modeling and static pile load tests results. The polynomial functional dependence of the load-settlement was obtained, with which a prediction of the numerical and averaged experimental curve \"load-settlement\" was made with an accuracy of 99.9%. 6. An economic comparison of the costs of the material and construction of ordinary piles and piles with a protective and load-bearing shell confirmed an extended economic effect of the developed technology of piling in a protective silicate shell with a significant reduction in the cost of piling, equal to 27.85%. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline Name & Name & Name & Name & Name & Name & Name & Name & Name & Name \\ \hline Piles with protective shell & & & & & & & & & \\ (2 x 4 m piles) & & & & & & & & \\ \hline Ordinary pile (5 pcs of 4 m & & & & & & & & \\ piles) & & & & & & & & & \\ \hline \multicolumn{8}{l}{584} \\ \hline \hline \end{tabular} Note: The cost of building a pile includes: delivery of equipment, installation and dismantling of equipment, pile with a pile head, and workers’ salary. The cost of the pile material includes: the cost of concrete and reinforcement. The volume of the shell material is calculated from the condition that sodium silicate is filled with 40% of the shell volume (\((0.42+0.42+0.4)\cdot 3.14\cdot 4-0.4\cdot 3.14\cdot 4\)) \(\cdot 0.4\cdot 2=8.44\) m\({}^{3}\); percentage economic efficiency is defined as: \(\frac{67900\cdot 64300\cdot 100\%}{879200}\cdot 100\%=27.85\%\).  
\end{table} 
Table 6: Calculation of economic efficiency of piles with protective shell. **Author Contributions:** Conceptualization, B.B.U. ; methodology, B.B.U. ; software, N.A. ; validation, B.B.U. and N.A. ; formal analysis, B.Z.U. and A.S.; investigation, B.B.U. ; resources, B.B.U. and A.S.; data curation, B.B.U. ; writing--original draft preparation, A.S.; writing--review and editing, A.S.; visualization, A.S.; supervision, B.Z.U. ; project administration, N.A. and B.Z.U. ; funding acquisition, B.Z.U. All authors have read and agreed to the published version of the manuscript. This research was carried out in the frame of the Ph.D. research of B.B.U., funded by the first author and partly covered by the educational grant of the Ministry of Education and Science of the Republic of Kazakhstan. Not applicable.