Vertical Shaft Sinking Machine (VSM)

Excavation and shaft construction in one step

Every Herrenknecht Shaft Sinking Machine consists of two main components – the shaft boring machine and the lowering units. The shaft boring machine is lowered into the launch shaft structure and attached firmly to the shaft with its three machine arms. A rotating cutting drum equipped with chisel tools is attached to a telescopic boom. This roadheader excavates and breaks the soil at the base of the shaft. The roadheader is telescopic, and can swivel up and down or rotate. Hence, the entire cross-section of the shaft plus an overcut can be excavated gradually. The excavated material is removed hydraulically through a submersible pump and transported to the separation plant on the surface. The lower concrete ring of the shaft structure, also referred to as the shaft’s cutting edge, is beveled and therefore cuts into the surrounding soil underneath. In addition, the overcut of the roadheader-like telescopic boom and cutting drum below the shaft’s cutting edge in combination with the bentonite lubrication in the annular gap reduce the frictional forces between the shaft wall and the surrounding soil. On the surface, 3 to 4 lowering units with hydraulic cylinders are attached firmly to the ring-shaped concrete foundation around the shaft. They are attached to the lower concrete base ring of the shaft structure by steel cables. In this way, the entire shaft structure can be held and lowered in a controlled manner during excavation. Ring building takes place simultaneously on the surface using prefabricated concrete segments. The simultaneous working processes (excavation, removal of excavated material, shaft construction, and lowering of the shaft structure) make it possible for VSM technology to achieve high advance rates of up to 5 meters per shift.

Step by step to a finished shaft

At the start of the drilling work, the shaft is flooded with water, creating a water circuit for overburden extraction and eliminating the need to lower the groundwater level. The separation plant separates the material from the water, which is pumped back. The structure is continuously drained while the ring excavation takes place on the surface. Once the target depth has been reached, the machine is recovered, the shaft is sealed with underwater concrete and the annular space is filled with mortar. Once the water has been pumped out, the shaft is ready for further use.

Everything under control from above

All operational processes are controlled and monitored from the surface. In addition to the separation plant, lowering units and recovery winches, the jobsite equipment includes a control container and power supply units. All information available about the excavation is collected and visualized in the control container. There, the operator has a full overview of the situation at hand and can respond accordingly at all times. After completing excavation or when changing excavation tools, the shaft boring machine is retrieved using the recovery winches. The advantages of the modular design of the overall system become particularly apparent in inner-city projects. The equipment can be arranged as needed. For example, the separation plant can be installed in a street next to the jobsite if there is not enough space for it next to the shaft.