The problems are discussed in three parts as follows: (1) When a surface, vertical, concentrated load is applied at a point on the level surface near the edge of sheet-piling cut, the active earth pressure stress against the sheet pile can be calculated by the formula of Boussinesq. The formula is now known as the standard by the Architectural Institute of Japan. In the book illustrating the standard, you will find useful tables and diagrams concerning the formula. However, when not a point load but a line load parallel to the sheet pile is applied on the level surface, such problem will be solved by integrating the formula as uniform load according to the approximate method. The author thought that in case a sheet of diagram is made beforehand, the integration does not have to be used. It is illustrated in Fig. 7 by the author. (2) Sometimes the slope around the surface of excavation on foot of sheet pile is remained in order to keep its proper situation of the sheet pile and to resist against the active earth pressure with the passive earth pressure. In this case the magnitude of the passive earth pressure depends upon the angle of the slope. Though Coulomb's method gives effective solution, there is some trouble to calculate many sections of slice and to find the least value of passive earth pressure. In stead of this trial method the author made the table of the coefficient "K" of minimum passive earth pressure applicable for such cases in order to eliminate the repeated calculation. The distribution of the pressure on sheet pile is not always linear with the depth. Especially when the angle of slope is close to the internal friction angle of the soil, the pressure distridution becomes smaller at the upper part of sheet pile. (3) In driving piles or sheet piles, if the ratio of the weight of hammer to that of pile is small, the fact that the efficiency of penetration becomes poor, can be proved by the theory of collision of two bodies in elementary kinetics. It is well known that some pile formulas have the terms containing the effect of the impact. In this report (here) the author shows the diagram of the above mentioned driving efficiency, which is the same as obtained from the formula of the collision of two bodies. And the influence of the ratio of the weight of hammer to that of pile on the driving efficiendy is made clear. In this diagram when the hammer takes upward velocity after the collision, the dynamic energy of the hammer after the collision is neglected in calculating the driving efficiency. The efficiency value for the diesel hammer is also plotted in the diagram. However, as the pile is contacted with the soil in various conditions, there come some difficult problems concerning the apparent weight of the pile. Nevertheless, such problem is not discussed here.