Predicting Geotechnical Parameters of Fine-grained Dredged Materials Using the Slump Test Method and Index Property Correlations

ERDC TN-DOER-D1

August 2004

Predicting Geotechnical Parameters

of Fine-grained Dredged Materials

Using the Slump Test Method

and Index Property Correlations

PURPOSE: This technical note describes an innovative method for estimating selected geo-

technical properties of physically remolded dredged materials using the proposed laboratory

slump test and correlation equations. Material property assessment requires laboratory testing of

dredged material samples. The index properties (including bulk density, void ratio, porosity,

water content, percent solids, Atterberg limits, and specific gravity) are ultimately needed as

geotechnical parameter inputs into the engineering planning, design, construction, operational,

and management aspects of dredging and dredged material placement. This technical note

explores innovative, non-standardized, and expedient methods to estimate numerous material

index properties and engineering behavior properties without running standardized time-

consuming and expensive laboratory tests. The proposed methods are presented only as optional

engineering tools based on experimental data and are not intended to usurp any standard labora-

tory testing protocol.

BACKGROUND: During nearshore dredging operations, the dredging process often involves a

large amount of material handling, manipulation, and remolding. By the time an original undis-

turbed (or previously deposited) material has been dredged, transported, and re-deposited, its

original geotechnical properties have changed. Dredged material is characterized by its physical

and engineering properties, and the level of detail needed to fully characterize those properties is

dependent upon factors such as the site geology, the dredging technique, and the dredged mate-

rial management plan. Numerous options are available for managing dredged material removal,

handling, and placement. For example, maintenance dredging may be accomplished by a trailing

suction hopper dredge with open ocean disposal, by a cutterhead dredge with pipelined beach

disposal, or by several other methods. The presence of contaminated sediments requires evalua-

tion of additional sub-strategies exploring proper disposal and/or treatment such as confined

aquatic disposal (Palermo et al. 1998).

For any dredging operation, the dredged material properties need to be measured or predicted.

The material properties are input into dredging operation and water quality models (such as

MDFATE, LTFATE, and ADDAMS), and accurate geotechnical parameters are required to pro-

vide realistic modeling similitude.

GEOTECHNICAL PROPERTIES OF REMOLDED SOILS: Dredged materials exhibit

properties similar to those of undisturbed native soil and rock materials in a subaqueous envi-

ronment, but when excavated, removed, remolded, or re-deposited, the properties change

accordingly as the original material structure changes. High water contents, low dry densities,

and low shear strengths typify remolded and deposited fine-grained dredged materials (Bartos

1977).