stabilization of soils by termites

Natural Stabilization of Soils With Special Reference to

Entomological Considerations

by

Dr.A.S.Nene and Y.D. Parihar

Termites, Wasps and earthworms can be considered

as soil engineers because of their effects on soil

properties.

Insects or Soil Engineers

v In nature there are insects that stabilize and

use soil for their dwellings. Such insects are

Wasps, Earthworms and Termites etc.

v The stabilization agents used by these insects are

yet unknown.

v Many ancient Indian Texts on Engineering mention

the use of ant-hill soils for mud plaster, mud flooring,

metallurgical crucibles and clay idols.

Introduction

Fascinating Facts about Termites and Termitarium (Ant-hills)

Ø Termites use adjacent soil grains for construction of

ant-hill.

Ø These particles are coated with sticky rapidly

hardening material secretions from mouth or rectum.

Ø On drying the material becomes hard as rock.

Ø Strength of the ant-hill increases with time.

Ø Ant-Hills are very strong and need sharp tools, or evendynamites to destroy.

Queen’s Chamber

Ø Size and shapes of termitarium are indicative of the species of termites.

Ø Shapes may like a mushroom,column, pyramid sheet piles etc.

Ø Size may be as large as 4 m. at base and height up to 9 m.

Ø On a scale of relative size, a man made pyramid would be4 km high !

Ø In spite of the huge soil mass used for giant ant-hills, there is no cavity in the ground.

Research Objectives

§ To study the engineering properties of ant-hill soiland compare with the properties of parent soil fromwhich the ant-hill are constructed.

§ To Conduct Chemical analysis of ant-hill soil for pH, phosphates and sulphate content.

§ To Conduct X ray Diffraction tests.

§ To Identify the secret of construction of ant-hills which will be very useful for low cost mud constructions.

The secret of construction of ant-hills

Cellulose54.6%

Pentosans18.0%

Lignin27.4%

Cellulose18.0%

Pentosans6.5%

Lignin75.5%

Food

Before Digestion After Digestion

1. Field visits and Samples collection

• Samples were collected from seven sites of Vidarbha.

• For each site two samples were collected.

• The first sample was of parent soil and the second sample was from ant-hill.

• About 10 kg soil samples were collected from each site for laboratory testing.

2. Laboratory Investigations Part 1

Following laboratory tests were conducted on 14 samples collected from seven sites.

Ø Differential free swell test (DFS )

Ø Grain Size Analysis (GSA)

Ø Consistency Limits (Liquid Limit -LL, Plastic Limit -PL and Shrinkage Limit -SL

S1 S2 S3 S4 S5 S6 S7

Site No

0

5

10

15

20

25

30

35

DF

S V

alue

%

Parent Anthill

Reduction in DFS Value and Nominal reduction in Liquid Limit

S1 S2 S3 S4 S5 S6 S7

Site No

30

35

40

45

50

55

60

65

Liqu

id L

imit

%

Parent Anthill

S1 S2 S3 S4 S5 S6 S7

Site No

10

12.5

15

17.5

20

22.5

25

27.5

Pla

stic

Lim

it %

Parent Anthill

Increase in Plastic Limit and Shrinkage Limit

S1 S2 S3 S4 S5 S6 S7

Site No

0

2.5

5

7.5

10

12.5

15

17.5

20

22.5

25

27.5

Shr

inka

ge L

imit

%

Parent Anthill

S1 S2 S3 S4 S5 S6 S7

Site No

0

10

20

30

40

50

60

Sw

ellin

g P

ress

ure

kP

a

Parent Anthill

Reduction in Swelling Pressure

Ø Swelling Pressure test (Constant volume method)

Ø Chemical Test on soils for pH

Ø Sulphate and Phosphate content test

Ø X Ray Diffraction test.

Laboratory Investigations Part 2

Laboratory tests were conducted on parent soils from three sites to find

Ø The effect of lignin on Consistency Limits of soils.

Ø The effect of lignin on dry density- Optimum moisturecontent of soils

CHandur Rajura Nagzira0

10

20

30

40

50

60

Liqu

id L

imit

%

0% 4 8 12

Effect of Lignin on Liquid LimitCHandur Rajura Nagzira

10

14

18

22

26

Pla

stic

Lim

it %

0% 4 8 12

Effect of Lignin on Plastic Limit

Decrease in Liquid Limit but increase in Plastic Limit

CHandur Rajura Nagzira12

16

20

24

Shr

inka

ge L

imit

%

0% 4 8 12

Effect of Lignin on Shrinkage Limit

Increase in Shrinkage Limit

Conclusions

Based on the review of literature and limited laboratory

investigations following conclusions were drawn.

vThe swelling characteristics of parent soils are drastically reduced in Natural stabilization by termites.

vThere is negligible change in soil Constituents of soil.

vLignin of the cementing material is the secret of strength of ant-hills.

vMore research is necessary to create similar cementing agent on large scale.

References

1. Eugene Marais (1973) “Sole of white ants”, Penguin Publications, London.

2. Roonwal M.L. (1979) Termite Life and Termite control. Scientific Publishers Jodhpur.

Ø Nene, A.S. and Parihar, Y.D. (1992)"Natural Stabilizationof Expansive Soil" Proceeding of Indian GeotechnicalConference 1992, Calcutta, 18-20 December 1992, Vol.1 .pp 207-209.

Ø Nene, A.S. and Parihar, Y.D. (1996) “Natural Stabilizationof soils with special reference to Entomological considerations" Second International Conf. On Soft soilEngineering, Nanjing (China) May 17-20.

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