Abstract: A method of constructing a vertical barrier wall in the ground (1,3) wherein two spaced apart, deep wells (2) are excavated in the ground. The walls (2) are interconnected near the bottom thereof by a substantially horizontally extending canal (7). Subsequently, there are provided in the wells (2) and the canal (7) a looped, closed chain (11) carrying excavators (12). The two ends of the chain are interconnected above the ground level. The closed chain loop is then driven in a direction of circulation and moved simultaneously upwards. The soil material 1 present between the wells (2) is thus "sawn through", thereby forming a narrow trench (26),which is filled with a supporting fluid (4).