GGU-CONSOLIDATE: Preface

If cohesive layers are loaded faster than they can expel their pore water, excess pore water pressures result, which are only gradually dissipated. This process is known as consolidation.

Settlement analyses to DIN 4019 do not take the fact into consideration that a large part of the settlement is often already complete during the construction phase. Most buildings are already being subjected to 80% of final loads by the time the shell is complete. Settlements, and therefore differential settlements, are generally non-critical at this stage, as they are manifested in masonry and other joints, which are then covered by pointing and paintwork in the "post-shell" phase. For cohesive soils in particular, therefore, a forecast of the temporal development of settlements, even for "simple" buildings, is an vital prerequisite for the safe judgement of possibly damaging differential settlements. The GGU-CONSOLIDATE program can assist you in these tasks.

The program system allows the analysis of one-dimensional consolidation processes in single and multi-layered systems. Any pore water distribution configuration may be defined. Using this program, you can also generate a pore water pressure distribution resulting from a foundation load. The de-watering conditions at the upper and lower layer boundaries can be defined separately. A load can also be applied to the system as a function of the time. It is also possible to take secondary settlements into consideration.

Beside the calculation of analytically derived solutions (Terzaghi), GGU-CONSOLIDATE is also capable of numerically modelling multi-layered systems. As well as classical consolidation theory, systems with installed vertical drainage can also be investigated. A combination of both systems (with and without vertical drainage) is also possible.

Thus, five different consolidation types are offered:

• Consolidation (analytical)
  One-dimensional consolidation theory after Terzaghi for a system with one layer and constant pore water pressure distribution across the whole layer depth at time t = 0. Modelling is performed using the analytical relationships given in the literature.

• Consolidation (numerical)
  One-dimensional consolidation theory after Terzaghi for a system with several layers and arbitrary pore water pressure distribution at time t = 0. Furthermore, loading can be defined as a function of time. Modelling is numerical, using difference equations. The modelling of one-layer systems with constant pore water distribution using available analytical solutions as described above can of course also be performed with the numerical model. Analytical consolidation has nevertheless been incorporated into the program, as this solution will always require shorter calculation times. Furthermore, you can check the very good quality of the numerical solution on simple examples.

• Consolidation (analytical) with vertical drainage
  Consolidation theory in a system with vertical drains. Pore water pressure dissipation is always directed horizontally towards the vertical drains. The pore water pressure is therefore temporally constant across the whole layer depth. Input of layer thickness in such systems is superfluous and has no influence on the temporal course of settlement.

• Consolidation (numerical) with vertical drainage
  In complete analogy to analytical modelling, a multi-layer system with vertical drainage can be processed. Here too, pore water pressure dissipation is exclusively horizontal towards the vertical drains. The pore water pressure is therefore temporally constant in each layer. As the pore water pressure is integrated across the layer for the whole time range, layer thickness input for multiple layer systems is important for the temporal settlement course, in contrast to one-layer systems.

• Consolidation (numerical) with both types
  It is possible to investigate systems in which vertical drains are only installed at a later, user-defined time.

All principal data and modelling results will be displayed on the screen. A total of five, or eight, graphical elements (see menu "Output preferences") can be presented:

• Legend with general information

• Table with the consolidation values at specified times

• Pore water pressure profile/consolidation ratio across the layer depth

• System visualisation

• Time-dependent development of degree of consolidation, settlement or pore water pressure

• Legend with soil properties (numerical modelling only)

• Type of load increase (numerical modelling only)

• Pore ratio diagram (only for calculation with the compression index C_C)