A calculation scheme suitable for studying the ground state of many-body Bose quantum systems with strong forces is developed. The calculation scheme is based on the nodeless property of the ground-state wave function and is capable of yielding in some cases upper and lower bounds on the ground-state energy and corresponding wave functions. From a treatment of liquid helium in the ground state, including a short-range interaction form, it is concluded that the calculation scheme is suitable for problems with involved interactions and is capable of reducing the problem to the mathematical one of calculation of the energy and lattice structure of a classical crystal at absolute zero of temperature.