Evaluation of the Compression Strength and Deformation Behaviour

Document Sample
Evaluation of the Compression Strength and Deformation Behaviour Powered By Docstoc
					Evaluation of the Compression Strength and Deformation Behaviour of Methane Hydrate Simulation Specimen

Nagasaki University

J.Nagaeki Y.Jiang Y.Tanabasi

Research background
Energy resource 【 Present 】 Fossil fuel(Petroleum・Natural gas)
There is a limit at the resources of the fossil energy.

【Future 】 The resources of fossil energy are limited

MH ( Methane Hydrate )

Methane Hydrate
MH

Cage state structure that the methane gas is surrounded for water molecule. Equilibrium under the condition of low temperature and high pressure .
Rangeland

The permafrost area In the sedimentary layer of sea bed
Distributed in the nearby sea area in Japan

About 100 times of the natural gas consumption per year of Japan

Production of MH
Production method Thermal stimulation method Temperature of the MH layer rises Decompression method Pressure of the MH layer lowers Ground deformation
Problem Interference of the production activity

Elucidation of mechanical characteristic and deformation characteristic of MH sedimentary layer

Purpose of the research
Purpose

To obtain basic data of MH sedimentary layer,which are necessary for further calculation and development.
Test outline

Temperature pressure Sand blend ratio

Compression strength Deformation characteristic

The manufacture of the dynamics test equipment

Ttriaxial compression tests are carried out in low temperature,using the artificial material which has the same properties with the sample.

The layout of test equipment
⑨
①

①heat storage layer ②pressureproof container ③low-pressure pump ④high-pressure pump ⑤flocon ⑥safety valve ⑦actuator ⑧air pressure line ⑨return line

⑥

⑧

②

④

⑤

⑦

③

The appearance of test equipment
①heat storage layer ②pressureproof container ③low-pressure pump ④high-pressure pump ⑤flocon ⑥safety valve ⑦actuator ⑧air pressure line ⑨return line

・temperature range : -30℃~+20℃ ・normal loading capacity : 100kN ・lateral pressure loading capacity : 10MPa ・pore pressure capacity : 10MPa

Gap sensors and the pressure vessel

Diameter : 30mm~100mm Height : 60mm~200mm

D=50mm H=100mm

Pressure and temperature control
①heat storage layer ②pressureproof container ③low-pressure pump ④high-pressure pump ⑤flocon ⑥safety valve ⑦actuator ⑧air pressure line ⑨return line low-pressure line high-pressure line return line
⑨ ①

⑥ ⑧
②

⑤

④
⑦

③

Trial test-piece
Sandy soil is used to simulate the sedimentary layer where MH stored.

Geologic material

Toyoura standard sand + fine powder ice ( screen passing material of 250 μm )

The test-piece manufacture
Laboratory Temperature : -5℃
3. It2. The mixing of Toyoura standard is compressed in the molding cylinder 1. Produced trial test-piece The crushing of the 4. Inside diameter powderice ( sand and fine : 50mm ice )

50MPa

Sand + fine powder ice

The molding cylinder

・軸載荷速度1%/min method Experimental
Mass ratio of Toyoura sand and fine powder ice Sand blend ratio
Testing condition and number of sample
Sand blend ratio (%) Test tempurature (℃) Lateral pressure (MPa) Sample (piece)

0

-5

2,6

2

30 50
70

-5 -5
-5

2,6,10 2,6,10
2,6,10

3 3
3

85

-5

2,6,10

3

Shaft loading rate 1%/min

Test result
Relationship between stress difference and axial 【 strain Lateral pressure 6MPa 】
Stress difference【σ 1-σ3】(MPa)

14 12 10 8 6 4 2 0 0

Strain hardening tendency
Sand blend ratio
Sand blend ratio 85% 70% 50% 30% 0%

Stress difference rise

Strain softening tendency
2 4 6 8 10 12 14 16
Axial strain【εa】(%)

Test result
Relationship between sand blend ratio and largest stress difference
20

Largest stress difference 【(σ1-σ3)max】(MPa)

Effect of the lateral pressure was high
16 12 8 4 0 0 20
Lateral pressure 2 Pa M 6 Pa M 1 M Pa 0

Effect of the lateral pressure was small

Largest stress difference rise
40 60 Sand blend ratio (%) 80 100

Test result
Relationship between axial strain and sand blend ratio
16

Axial strain(%) Axial strain 【εa】(%)

14 12 10 8 6 4 2 0

Lateral pressure

2M P a 6M P a 10M P a

Axial strain increase by the strain effect tendency

No effect by the lateral pressure

0

20

40

60

80

100

Sand blend ratio(%)

Test result
Relationship between sand blend ratio and distortion calculation
Et:Tangent modulus E s:Secant coefficient Distortion calculation【E】(MPa)

2400 2100 1800 1500 1200 900 600 300 0 0 20 40 60 80

Lateral pressure
2M P a Et 2M P a Es 6M P a Et 6M P a Es 10M P a Et 10M P a Es

Distortion calculation decreases, as sand blend ratio increases
100

Sand blend ratio (%)

Test result
Relationship between sand blend ratio and shear strength
Shearring stress【τ】(MPa)
10 8 6 4 2 0 0 2 4 6 8 10 12 14 16 18 20
Sand blend ratio85% The lateral pressure dependence is high Sand blend ratio70%

The lateral pressure dependence is less Internal frictional angle(φ) is around 1°

Normal stress【σ】(MPa)

Conclusions
Low temperature triaxial compression test apparatus was manufactured. Manufacturing method of the MH simulation test-piece and test procedure were established.

The triaxial compression test which set test temperature at -5℃ was carried out. The relationship between sand blend ratio and distortion calculation and strength constant of the trial test-piece was examined.

Conclusions
Sand blend ratio Take great effect on the relation between axial strain and stress difference. Take great effect on the change of distortion calculation. Lateral pressure dependence Lateral pressure dependence is high for the sample of the 85% sand blend ratio. Lateral pressure dependence is very low for the sample of 70% sand blend ratio or less.

Conclusions
Shear strength and sand blend ratio 【Internal frictional angle】 Sand blend ratio 70% or less : φ= 1°
From these results

It was possible to obtain the part of basic data of the MH sedimentary layer,which are necessary for the development of the consolidation calculation module.

Future 今後の展望
Test temperature -1℃ ~ -10℃

prospect
Trial test-piece containing actual MH

Temperature dependency of deformation characteristic and strength constant

Dependence by the existence of the methane of distortion calculation and strength constant

Development of the consolidation calculation module

END

模擬供試体の飽和度
120 100

飽和度(%)

80 60 40 20 0 0 20 40 60 砂配合率( %) 80 100
砂配合率70%以下

飽和

不飽和

氷体積 飽和度  氷体積  空気体積

模擬供試体の間隙率
100 90 80 70 60 50 40 30 20 10 0 0 20 40 60 砂配合率( %) 80 100

間隙率(%)

氷体積  空気体積 間隙率  全体積

模擬供試体の間隙比
8. 0 7. 0 6. 0 5. 0 4. 0 3. 0 2. 0 1. 0 0. 0 0 20 40 60 砂配合率( %) 80 100

間隙比

氷体積  空気体積 間隙比= 砂体積

MHの構造
メタン

結晶構造 かご構造(正12面体) 赤玉:酸素原子 白玉:水素原子
特定の条件下において、数十個の水分子が結 合

駕籠(かご:クラスター)構造という特殊


				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:13
posted:9/15/2009
language:English
pages:26
Lingjuan Ma Lingjuan Ma
About