On Predicting Settlements by CPT

 

Robertson (1986). CPT predictions of soil modulus from the cone resistance can be rather poor, especially for overconsolidated soils, with a large potential error.

Powell (BRE) (2012). The scarce ability to predict modulus is a well known weakness of CPT.

Been SOA at CPT (2010). If purpose is parameters, CPT cannot be used in isolation – must be supplemented by laboratory or other methods. CPT can easily mislead in terms of soil type, strength and particularly modulus.

Jamiolkowski (Isopt-1 1988). Without Stress History it is impossible to select a reliable E (or M) from Qc (similar statement by Terzaghi, Leonards, Schmertmann…)

Leonards & Frost (1988). Correlations between penetration resistance and soil modulus will seriously overestimate settlements if the deposit has been prestressed.

Lambrecht and Leonards (1978). Prestressing increased the modulus by one order of magnitude, while Qc had only a slight increase.

Schnaid (2009). Correlations between cone tip resistance and soil stiffness are unreliable.

 

On Predicting Settlements by DMT

 

Schmertmann (1986). A DMT sounding can usually provide the data needed for the calculation of expected settlements with an accuracy adequate for most practical purposes.

Penna (2013). In my practical experience the DMT is the best approach for settlements prediction

Leonards (1988). It has been argued that, at the present time, the Marchetti dilatometer is the most generally applicable practical tool for sensing soil compressibility

Mayne (2004). Over two decades of calibration between the DMT and measured foundation performance records have shown its value & reliability in settlements computation.

Crapps (2001). Users prefer DMT data over any other soils data to estimate settlements. A user with Law Engineering in Atlanta told me yesterday that the settlements are “always right on (meaning close to) the predictions from DMT”.

KCI Technologies Usa (2000). By DMT a more cost effective design can result, producing savings in construction cost.

Tice & Knott (2000). Good agreement was observed between DMT-predicted and measured settlements at the sandy site under Cape Hatteras Light Station.

Steiner (1994). An earthfill on a loose sandy-silt produced settlements substantially higher than anticipated based on conventional soil borings. DMT were then performed. “The DMT-predicted settlements agreed well with observed settlements”.

Woodward & McIntosh (1993). Use of modulus from DMT permitted considerable savings. Using DMT, the structure was able to be constructed successfully on a shallow foundation system without utilizing more expensive and time consuming soil improvement techniques.

Geopac Quebec (1992). Settlements predicted by PMT and DMT were very similar, but cost and time for DMT were a fraction of PMT

Failmezger & Bullock (2011). DMT is a static deformation test that strains the soil to intermediate strains. Tests are generally performed at depth intervals of 0.20 m. Tests typically take about 1 minute to perform. DMT is therefore the best choice of in-situ tests for settlement prediction of shallow foundations.

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