Based the on soil mechanics,elastic theory and some reasonable assumptione,adopting the method of the equal settlement section,considering the pemetration of top and fir of pile,the calculation formula of composite foundation with capped rigid pile was proposed,which showed the characteristics of layered soil and its 3D settlement deformation.

There is equal settlement section in the reinforced area of the composite foundation,the sparse capped pile settlement controlled composite foundation can enhance the stability of soft ground.

The effect factors of the distance of two piles, the length of pile, size of pile cap, modulus of cushion, modulus of underlying soil layers, modulus of soil besides pile cap and K_0 have been discussed for composite pile-soil stress ratio and the place of equal settlement section. 4. Based on reasonable assumption and elasticity theory, adopting the load transfer function method, the linear analysis of composite single pile with cap has been done.

The investigation indicates that the settlements of bearing plate approximate to the settlements of surface of soil around pile, the settlements of pile top is markedly greater than the settlements of surface of soil around pile,the deformation of pile and soil don′t meet the equal strain condition,there exists an equal settlement plane in specified depth L0 in composite ground,in which the settlements of pile equal to the settlement of soil around pile.

Based on soil mechanics and elastic theory, the correspondence equation of the vertical deformation of the composite foundation of the stiff pile and the half stiff pile is derived in this paper. The mathematics formula of the cushion thickness and compression modulus of influence on the composite foundation of the stiff and the half stiff pile is derived. Based on it, influence of the different cushion thickness and compression modulus on the stress ratio of pile and soil, on the location of the greatest stress...

Based on soil mechanics and elastic theory, the correspondence equation of the vertical deformation of the composite foundation of the stiff pile and the half stiff pile is derived in this paper. The mathematics formula of the cushion thickness and compression modulus of influence on the composite foundation of the stiff and the half stiff pile is derived. Based on it, influence of the different cushion thickness and compression modulus on the stress ratio of pile and soil, on the location of the greatest stress and the greatest stress in pile, on the load transfer in pile and soil is determined. The conclusion of relaxing stress concentration on the pile top by improving the cushion thickness and lowering the cushion modulus is obtained, but the location of the equal settlement section is lowered. On the contrary the stress of the pile end is increased. So it isn′t useful to excessively increase the thickness and lower the cushion modulus to acquire lower stress ratio of pile and soil. Synthesis analysis indicates that the best cushion thickness is 0.2～0.5 m and the best compression modulus of the cushion is 30～100 MPa. This cushion thickness corresponds with the thickness used in engineering. The optimized design on the composite foundation of the stiff and half stiff pile by the cushion can be performed with this method.

The article makes a realistic exposition of the function of rigid combination beams of weak base foundation deduced with theories.It is tested and proved that setting up rigid combination beams on a weak base foundation can effectively transmit the heavy load of the upper construction part evenly to the base to make an equal settlement.As a result,the foundation can be safe and reliable.The theoretical inference tallies with the practice.

Plastic model is used for the earth fill and elastic model used for the foundation. Based on the conditions of force equilibrium and deformation accordant, the vertical pressure on top of culverts is studied. The calculation formula obtained contains some parameters, such as the size of culverts, the depth of earth fill, the characters of the foundation and earth fill etc. The calculation result shows that the depth of equal settlements surface increases as the increasing of the foundation elastic modulus...

Plastic model is used for the earth fill and elastic model used for the foundation. Based on the conditions of force equilibrium and deformation accordant, the vertical pressure on top of culverts is studied. The calculation formula obtained contains some parameters, such as the size of culverts, the depth of earth fill, the characters of the foundation and earth fill etc. The calculation result shows that the depth of equal settlements surface increases as the increasing of the foundation elastic modulus and earth pressure coefficient on the top of culverts is showing a tendency to increase first and decrease afterwards along with the increasing of the earth fill depth.