Influence of Radial Coefficient of Consolidation on Ground Improvement in Soft Clay with Vertical Drains

Abstract

Very soft and soft clays are to be consolidated to enable them to support embankments supporting highways/railways, heavy duty pavements at container yards and to support runways. Such clays are predominant along the sea coast with thickness of layers extending to large depths. Among different ground improvement options, strengthening of soft clay by vertical drains with preloading is the best option and is preferred by engineers (Sarika S, Deepankar C, Salunkhe JS (2015) Ground improvement of marine clay for highway construction at Mumbai, India. IFCEE ASCE 2015; Kumar Pichumani N, Aminul I (2021) Reclamation and ground improvement of soft marine clay for development of offshore terminal 4, JNPT, Navi Mumbai. Indian Geotech J-021-00521-y). The ground treatment time with vertical drains depends on consolidation characteristics of soft clay for proposed drain with given spacing. Prefabricated vertical drains (PVDs)/geocomposite drains are widely used as they are efficient over other forms of drains. Often, designers consider the value of radial coefficient of consolidation based on the value of vertical coefficient of consolidation. Earlier studies on soft marine clays have reported the ratio of radial to vertical coefficients of consolidation to vary from 1.5 to 4 (Chu et al. in J Geotech Geoenvironmental Eng 2002:724–732, 2002, Marchetti et al. 2004). In the present paper, the influence of radial coefficient of consolidation on the treatment time for soft clay at one of the stacking yards of Visakhapatnam port trust is evaluated from 3-dimensional consolidation. The design of ground improvement system with PVD and preload is done for different values of radial coefficient of consolidation to highlight its influence in ground improvement program in soft clay. The study revealed that the overall degree of consolidation (U) is not much affected for cr/cv values of 2.5–4.0 at closer spacing of drains (0.8 m) as the variation in values of U is about 5%. Further, in triangular pattern arrangement of drains, the variation is relatively smaller compared to square pattern arrangement of drains.KeywordsSoft clayGround improvementPreloadingVertical drainRadial consolidationCoefficient of consolidation