In this study, PLAXIS is used for surface and subsurface settlements in underground monumental structures in the valley of kings at Luxor, Egypt; predicting differential settlements of buildings adjacent to excavation; planning for stability and seepage into underground structures or lateral displacements of diaphragm walls; calculating necessary consolidation time for pore pressure dissipation in undrained loading problems; or estimating bearing capacity and foundation settlement analysis for historic masonry structures, and other structures.
PLAXIS 3D offers CAD-like drawing capabilities to help with the analysis of subsurface environments for geoengineering projects. From excavations, embankments, foundations, tunneling, and mining, to reservoir geomechanics, users can determine the deformation and stability of geotechnical engineering and rock mechanics to assess the geotechnical risk.
The computed static surface ground displacements under Abu Serga church are in high values: maximum total vertical displacements is 122.85 mm, which is not acceptable or permissable. Many researches like [27,28,29,30,31,32] discussed the permissable maximum settlement for the shallow foundations in clay soils; and indicated that, for the loading bearing walls, the permissible maximum settlement is 60 mm in case of isolated footings, and 125 mm in case of raft foundations.
The Intervention and strengthening measures and work for the church included the improvement of the subsoil layers, reinforcement of the shallow foundations and the strengthening of the superstructure the church. Table 4 summarized the main aspects of structural strengthening of architectural heritage.
When the structural elements are capable of taking care of the total weight of the historical construction structure. Improvement of shallow foundations found by low pressure injection of hydraulic lime mortar was necessary.
In order to solve the problem of insufficient bearing capacity of existing concrete piles, a type of concrete pile with an additional lengthened strengthening core is designed, by inserting the steel tube through guiding hole and pouring core concrete. To reveal the mechanical performance of the reinforced piles, scale model tests and finite element simulations were performed. The results showed that both the vertical and horizontal bearing capacity increase with the length of the stiffening core. The axial force of the enhanced core is also smaller than conventional concrete piles, and the extended core can share the axial force of the foundation pile to improve the stress distribution of the pile body. These findings point toward a useful and general method for increasing the load capacity of existing concrete piles.
Due to the characteristics of high bearing capacity, reliable construction quality, and wide range of application, concrete filling piles have been widely used in all kinds of new construction and reconstruction projects. However, because of many uncontrollable factors (such as soft soil around the pile, concrete segregation, and sediment at the bottom of the pile), engineering problems such as pile defects, insufficient bearing capacity, and even broken pile are inevitable, which have a negative impact on the bearing capacity and construction efficiency of the foundation pile to a certain extent.
The above research work or treatment measures are helpful to improve the bearing capacity of RC piles and can be used to solve the quality problems of slightly defective piles and some obviously defective piles. However, for obvious defective piles and seriously defective piles (e.g., complete fracture of pile body and insufficient pile length) in engineering projects with strict quality requirements (such as in high-grade highway projects), and the old defective piles in the reconstruction and expansion projects, the applicability of existing technology will be limited to a certain degree. At present, these heavily defective piles are usually treated by in situ rework or additional piling, which not only increases the cost of foundation pile construction but also raises the risk of engineering construction and even causes design changes, which seriously affects the progress, benefit, and construction environment of the related engineering projects.
In view of this, in order to improve the retention ratio of concrete piles with obvious and serious defects in new projects, as well as old concrete piles in reconstruction and expansion projects, it is necessary to carry out further research on the treatment technology, so as to solve the two key problems, i.e., the retaining of existing concrete piles and improvement of the bearing capacity of pile body. Considering the key factors of these two problems, this paper proposes a new type of concrete pile structure with lengthened strengthening core. Different from the existing technologies, through piloting hole in the pile core, this new foundation pile structure is formed by concrete pile and a lengthened strengthening core whose length is larger than the pile. On the basis of expounding the basic form of the structure, this paper studies the bearing capacity of the proposed pile structure through reduced-scale model tests and numerical simulations.
The remaining of this paper is organized as follows. In Section 2, an introduction to the new foundation pile is presented. Following, details about the scale model tests are reported in Section 3. Next in Section 4, finite element simulations in close accordance with experiment work are carried out to further reveal the performance of the proposed pile. Finally, conclusions are made in Section 5.
In this paper, a concrete pile reinforced by strengthened steel tube was proposed. Both scale model tests and numerical simulations were carried out to examine the mechanical behaviors of the presented pile (e.g., the vertical and horizontal bearing capacity, axial force, lateral friction resistance, and bending moment). Through the above studies, the following conclusions can be drawn:(1)The designed pile with lengthened strength core meets the requirements of existing pile retention and bearing capacity improvement.(2)The vertical compressive bearing capacity of the pile increases linearly with increased length of the strength core. The axial force of the pile is smaller than that of the conventional concrete pile, and the lengthened section can share the axial force of the foundation pile and improve the stress distribution of the pile body.(3)The lateral bearing capacity of the pile with lengthened strength core is obviously higher than that of the conventional pile, but when the lengthened proportion exceeds 50% of the length of the original pile, the increase in lateral bearing capacity slows down.(4)The simulation results show that the friction force between pile and soil can be better exerted by the pile with lengthened strength core. When bearing the horizontal load on top of the pile, the stress in the passive zone of the pile is concentrated at the pile bottom and the variable cross section, and there is obvious stress spread phenomenon in the lengthened section. 1e1e36bf2d