Effect of Bio-Cementation on

Cone Penetrometer Measurements Collin M. Anderson, M.S. (June 11, 2015)

Advisors: Jason T. DeJong & Douglas C. Nelson

1.Both bio-stimulation and bio-

augmentation work, and are

comparable at the large scale.

2.Attempting to detect lightly

cemented soil using only tip

resistance and sleeve friction

ratio is shown to be unreliable.

3.The best indication of lightly

cemented soil is evidence of

calcite.

The project was possible with

funding from the National

Science Foundation. The help,

advice and patience from

Michael Gomez, Prof. DeJong,

Prof. Nelson, Bill Sluis, Daret

Khalet, Matt Havey, Steve

Purugganan, Charlie Graddy,

and Jason Wong is also

acknowledged.

MICP (Microbially Induced Calcite

Precipitation), or bio-cementation, is

a novel process by which bacteria in

soil are stimulated to produce a

cementing compound, Calcite

(CaCO3), at the particle-particle

contacts resulting in drastically

increased strength. Large scale tests

were performed to evaluate feasibility

of field testing and quantify behavior

of cemented soil during cone pushing

(not possible at small scale).

Eight cone soundings established

baseline conditions and assed soil

uniformity.

Spatial mapping of qt values at mid

depth confirm the pumping method

achieved the goal of creating gradients

of cementation.

Results of averaged values at mid-depth (ΔVs1 and ΔGo) and full

depth (calcite) vs. average Δqt1n at that depth (± 2.5 cm)

30 full depth soundings performed post treatment quantified behavior of cemented soils during CPT

testing. Five typical profiles are presented for qt, qt1n. Δqt1n, and fs for the Bio-stimulation. Mid depth

averages between tanks were nearly identical (see Spatial Variability).

Averaged values at mid-depth with calcite contours shown in red

Region B

Region A

Region C

Yolo

Loam

Top Cap

Concrete

Sand

String Pot

To DAQ

SystemSteel Cross

Beams Mini-

Cone

Smooth

Sleeve

Waterproof

Rubber Liner

2,000 lbs. Load

Thin, Plastic

Liner

Bio

-Stim

ula

tion

B

io-A

ugm

enta

tio

n

3%

5%

1%

3% 5%

1%

Me

asu

red

tip re

sis

tan

ce

, qt (M

Pa

)

W1

W2 W3

W1

W2 W3