Industrial plants and civil houses are often complex in shape, with I-shaped, L-shaped and T-shaped on the plane, with height difference changes, and sometimes masonry structures are connected with bent structures. As for the stage, library, gymnasium and other buildings, it is more complicated. The settlement observation data show that the parts where the building plane, elevation and structure change are often the parts where the foundation deformation is quite different and the wall is easy to crack. Therefore, the following measures should be taken in the design: ① The body shape should not be too complicated, the height and load of the same building should not change too much, and the longitudinal wall of the house should not be interrupted or tortuous. ② Divide the whole house into several basic units, and the length-width ratio of each unit should be less than 2.5, so that each unit has independent and good stiffness and the ability to adjust uneven deformation. (3) The structure and load of each unit should be as same as possible. If the structure and load of two adjacent units are obviously different, the settlement of each part of the building should be calculated, and the possible problems in the unit with weak structure and light load, such as adjacent high and low floors, should be studied, and the influence of high floors on low floors should be considered. If necessary, the foundation form or construction procedure must be changed, such as building a high and heavy part first, and then building a low and light part after its completion. Settlement joints should be left between units; If possible, simply supported beams can be used for connection. (4) Multi-storey houses with weak lateral stiffness or without internal transverse walls, especially double-span frame structures, in which the column load is large, the lateral deformation will be uneven, and the settlement difference calculated through deformation should be less than 0.003l(l is the column spacing).
In modern industrial areas or big cities, the spacing between buildings is very small, which often leads to buildings tilting. After the inclination exceeds the allowable value, it is not conducive to use and safety. The amount of tilt can be determined by calculation. If it can't meet the use requirements, it can be solved by pile foundation in one of the two adjacent buildings.
In the foundation design of high-rise buildings, box foundation and basement compensation foundation are often used to meet the requirements of foundation bearing capacity and settlement. The principle of this method is to reduce the additional stress in the foundation and increase the stiffness of the foundation through the excavated earthwork, thus reducing the settlement and increasing the stability of the foundation. The compensated foundation also has good seismic performance in the earthquake area.
Foundation design under large-area ground load All kinds of warehouses, wharf warehouses and high fill soil will cause ground settlement, uneven rotation and subsidence of pile foundation and wall foundation, and in serious cases, columns and walls will be broken and cranes will slip. According to a large number of field investigations, natural foundation can still be used when the pile material is generally less than 3 tons/m, but attention should be paid to the uneven trajectory of the crane and the collision between the top of the crane and the lower chord of the roof truss. At the same time, the section and reinforcement of the column should be appropriately increased; It is forbidden to pile materials on the foundation. When the average pile material exceeds 3 tons/m, it is necessary to determine whether natural foundation can be used by calculation; Column foundation piles should be set up when necessary. Because the number of open-air piles does not involve building safety, technical measures can be determined according to the requirements of lifting equipment, but the stability of foundation should be checked. Commonly used treatment methods are divided into three categories: ① Preloading is to reduce foundation deformation and increase foundation bearing capacity. In order to shorten the preloading time, the sand drain method is often used, but its use is limited because of the large amount of surcharge required for preloading. At present, there is vacuum drainage preloading method, and the effect is very good. ② Sand cushion (see soil replacement method) and gravel pile (see vibroflotation method) are used, and these methods have good effects in thin soil layer. ③ Rigid piles, such as reinforced concrete precast piles, cast-in-place piles and steel pipe piles, are adopted, which are suitable for heavy structures or buildings with strict settlement requirements; After the pile foundation is adopted, there is no need to set settlement joints in the upper structure or take strict measures in the structure, but the cost is relatively expensive.