Some Classical Terzaghi Primary Consolidation Differential Equation Mathematical Added Variabilities in Order to Get Better Field Monitoring Data Match Results

In this paper is illustrated a mathematical added variability of the classical Terzaghi primary consolidation equation(1923)considering independently as variables the Consolidation Coefficient Cv and as well the Height Hi of the consolidating Laboratory Consolidation Test soil sample in order to finally grasp the low permeability layer time behaviour.It is easy to show that,when the Cv variation is positive,each of these two added variabilities differentiations has as maximum a factor 2 related to the laboratory evaluated coefficient of consolidation,for a certain incremental load of reference in a Laboratory Consolidation Test.At this scope,it is analysed the overall behaviour of a typical clayey material,from the mineralogical point of view,namely especially either composed by lean clay with main kaolinite mineralogical content or fat namely with Illite mineralogical content or even very dilatant namely principally constituted by Montmorillonite.The Montmorillonite variability with Cv is negative,and consequently the differentiation enhancement factor can become naught.As it is known so far,in normal conditions of a soft clay,a difference in Construction Values of the Coefficient of Consolidation is up to 23 times greater than laboratory evaluated results,and this according to the author’s experience,may be also mainly explained not starting from Laboratory Consolidation Test Data,but through a more general macroscopic behaviour of the soil underneath the newly loaded area,putting aside the case of temperature-induced changes.In conclusion,it is suggested how to model the analytical problem of the so modified Terzaghi Primary Consolidation differential equation in order to better manage the construction unknowns of the phenomenon.

Delta River Swampy Areas Earth Fill Embankments Primary Consolidation Management Issues

It is well known that soft silty clayey and even peaty soils especially existing in Great River Deltas Swampy Areas,under important Earth Fill Embankment Construction experience huge and hardly bearable primary consolidations settlements along with the minor but not negligible consequent secondary consolidation effects.In order to properly manage these particular huge settlements environments,it is very important to follow up the settlements monitoring data,by a macroscopic soil volume interpretation along with some amendments namely some mathematical added variabilities of the classic Terzaghi Primary Consolidation Equation,which are examined in a companion paper recently published in this Journal.In this paper some indications are given about how to face the macroscopic soil volume primary consolidation settlements,and especially it is suggested how to interpret the misleading laboratory consolidation test values of the coefficient of consolidation.Moreover,some design alternative solutions are examined to grasp both the potential technical and economic benefits along with their consequent disadvantages.Finally,this paper underlined the primary role of the supervision engineer to get a good estimate in the settlements forecasting and his related ability to understand the meaning of anomalous monitoring data and to timely make and match the primary consolidation settlements forecasting calculation adjustments.

No Rupture Surface Sliding Geo-Technique in Deep Excavation for Static and Especially for Seismic Thrust

In the recent literature concerning the multi-propped bottom-up technique Shanghai Metro Stations Excavations, there is evidence of the importance of the disturbance in terms of greater wall horizontal deflections and consequently vertical settlements in the neighbouring, caused by the late long time of open -cut excavation without propping. Here is proposed, theoretical and pragmatic at the same time, a new approach to face the problem of the wall deflections and the related vertical settlements behind the wall. The solution proposed is indeed to impede any formation of the incipient sliding in the active wedge soil rupture surface, by oblique piling crossing over the rupture surface through a longer pile penetration length in relation to the active wedge before any excavation process starts. This piled-construction will then cut to shape the excavation profiles recurring to loss of piles material. This solution is particularly fit for high seismicity prone areas, because of the minor relative loss of per unit length of pile, caused by the greater depth of the rupture surfaces to get and cross over.