A method for constructing retaining wall structure and wellpoint in granular soils under groundwater level, comprising the steps of:
- providing a hammering casing pipe system comprising,
- a casing with a hollow cylindrical configuration having a first end and a second end comprising, at least two half-cylinders attached around an upper end of the casing for hardening the upper end, a steel ring disposed above the casing to harden and avoid bending of the casing, one or more vertical stiffener plates attached around the steel ring and the at least two half-cylinders, and at least one eye bar plate disposed at each half-cylinder, an impact transmission shaft coupled to a hammer element, and
- an inner shaft assembly disposed within the casing, the inner shaft assembly comprises a top portion, a middle portion and a bottom portion, the middle portion and the bottom portion are configured to insert within the casing, into the soil and prevents soil entering into the casing,
- the top portion of the inner shaft assembly comprises a mandrel head configured to transmit impact from the hammer element, a stepped cylindrical segment extends from the mandrel head configured to maintain a position of the inner shaft assembly, a lower cylindrical segment extends from the stepped cylindrical segment, the lower cylindrical segment having a diameter lesser than a diameter of the stepped cylindrical segment,
- the middle portion of the inner shaft assembly comprises at least six guide triangular plates disposed around the middle portion of the inner shaft assembly and at least six connector plates coupled to the at least six guide triangular plates, respectively, wherein the at least six guide triangular plates and the at least six connector plates are coupled to the lower cylindrical segment via an intermediate segment, and
- the bottom portion of the inner shaft assembly comprises a hollow cylindrical segment, a bevelled hollow cylindrical segment extending from the hollow cylindrical segment, and a conical segment extending from the bevelled hollow cylindrical segment configured to allow smooth penetration and prevention of soil entering into the casing pipe;
- positioning the hammering casing pipe system above a target location;
- generating a cavity by driving the casing using an external hammer element;
- removing the inner shaft assembly from the casing positioned in the cavity;
- providing a vertical beam and a drainage pipe fastened to the vertical beam;
- inserting the drainage pipe fastened to the vertical beam into the casing;
- removing the casing from the target location;
- connecting the drainage pipe to a horizontal pipe connected with one or more water discharge pumps for lowering groundwater level;
- installing a welded mesh behind the vertical beam and one or more shotcrete layers on the target location;
- hammering one or more steel grooved pipes to a cross formed of a shotcrete layer and welded mesh, the hammering occurring at a target location under high frequency;
- sealing a steel grooved pipe crossing the shotcrete layer and welded mesh, and dewatering the target location using the drainage pipe and stabilizing the target location with the vertical beams and nailed steel grooved pipes.