應用等值參數於深開挖地盤改良分析之研究｜國立臺灣科技大學博碩士論文系統

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研究生：	蕭奎仁 Kuei-Jen Hsiao
論文名稱：	應用等值參數於深開挖地盤改良分析之研究 Use of equivalent parameters for ground improvement piles in deep excavation analysis
指導教授：	歐章煜 Chang-Yu Ou
口試委員:	林宏達 Horn-Da Lin 廖瑞堂 Jui-Tang Liao 謝百鈎 Pio-Go Hsieh
學位類別：	碩士 Master
系所名稱：	工程學院 - 營建工程系 Department of Civil and Construction Engineering
論文出版年：	2016
畢業學年度：	104
語文別：	英文
論文頁數：	95
中文關鍵詞：	深開挖、地盤改良、柱狀改良、等值參數
外文關鍵詞：	Deep excavation, ground improvement, improvement pile, Equivalent parameter
相關次數：	點閱：325 下載：11
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地盤改良工法經常運用在提升開挖的穩定性，在柱狀地盤改良中，常將土壤和水泥混合形成改良土，而改良後的土壤，於改良區中與未改良土形成複合材料。一般在分析設計上，等值參數常用於模擬複合材料的工程參數，然而，開挖區內的機制複雜，對於運用評估複合土之等值參數需加以評估。本研究首先利用有限元素法模擬三軸試驗，以驗證前人研究所提出之等值參數評估公式。將複合土體進行軸向壓縮(AC)、軸向伸張(AE)、側向壓縮(LC)模擬試驗之結果與前人之評估公式比較後，得到相符之結果。然後，利用三向度有限元素分析以及二向度平面應變分析，對一個柱狀改良之假設開挖案例分別進行實際配置模擬以及等值參數模擬。由三向度分析之結果發現，改良樁之強度在開挖行為中幾乎由抗拉強度控制，藉由這現象，本研究推導一等值強度公式，並運用在二向度平面應變分析。在二向度平面應變分析中，改良區內之土壤及改良樁，經由等值參數公式轉換成等值材料。將等值參數模擬與實際配置模擬之壁體變位分析結果作比較，顯示經由兩個方法所得之壁體變位相近，且最大壁體變位比值可達0.99以及1.01。即利用二向度平面應變分析能有效的模擬分析柱狀地盤改良後之深開挖行為。

To increase the stability of the excavation, ground improvement techniques are commonly used. With the column type of the ground improvement, the soil was often mixed with the cement to make the soilcrete. The improved soil within the excavation zone thus forms a composite material. The engineering properties of the composite material are usually simulated by the equivalent parameters. However, with the complicated mechanism within the excavation zone, the performance of the equivalent parameters needed to be evaluated. In this study, the proposed equivalent parameters equations were investigated by using the finite element method (FEM) with the simulation of triaxial test. The axial compression (AC) test, the axial extension (AE) test, and the lateral compression (LC) test with the composite soil sample were modeled in the finite element analysis. The FEM results yielded close results with the proposed equivalent parameters equations. Furthermore, a hypothetical excavation case with ground improvement piles was adopted in the 3D and 2D finite element analysis. In the 3D analysis, the real allocation simulation of improvement piles was performed. Results showed that the strength of the improvement piles mostly depended on the tensile strength of the pile. In addition, an equation was derived to estimate the equivalent strength of the composite soil within the improvement zone. In the 2D analysis, the equivalent material simulation was performed. The soil and the improvement piles within the improvement zone was regard as an equivalent material which was calculated from the equivalent parameters equations. Results showed that the 2D analysis can yield as good as the 3D analysis on the wall displacement. The maximum wall displacement ratio can reach 0.99 and 1.01 for the closest results. Therefore, the 3D condition of the improvement piles can be analyzed with the 2D analysis.

Table of contents
中文摘要.....	I
Abstract.......	II
致謝...............	III
Table of contents	IV
List of tables	VI
List of figures	VII
Chapter 1	INTRODUCTION	1
1.1 Background	1
1.2 Objectives	1
1.3 Thesis structure	2
Chapter 2	LITERATURE REVIEW	3
2.1 Properties of Soilcrete	4
2.1.1 Compressive strength of Soilcrete (qu)	4
2.1.2 Tensile strength of Soilcrete	5
2.1.3 Young’s Modulus of Soilcrete	5
2.2 Properties of Composite soil	5
2.2.1 Parameters for composite soil using Mohr-Coulomb model	6
2.2.2 Composite soil behavior under different stress path	7
2.3 Prediction of composite Young’s modulus and shear strength	8
2.3.1 Rule of mixtures	8
2.3.2 Halpin-Tsai equation	9
2.3.3 Wu (1994)	10
2.4 Summary	11
Chapter 3	FINITE ELEMENT OF TRIAXIAL TESTS ON A COMPOSITE SOIL………………………………………………………………………………………………………………………21
3.1 Parameters of soilcrete and clay	22
3.2 Axial compression test (AC test)	22
3.3 Axial extension test (AE test)	24
3.3.1 Tension cut-off	24
3.3.2 Boundary condition with and without plate element	25
3.4 Lateral compression test (LC test)	25
3.5 Summary	27
Chapter 4	EFFECTS OF IMPROVEMENT PILES IN DEEP EXCAVATION	44
4.1 FEM with reduced shear strength	44
4.2 Hypothetical excavation case	45
4.3 Stability analysis	47
4.4 Excavation mechanism in improvement zone	48
Chapter 5	DERIVATION OF EQUIVALENT PARAMETERS	63
5.1 Hypothetical case model with plane strain analysis	63
5.2 Establishment of equivalent parameter equations	64
5.2.1 Equivalent parameters using the MC-Undrained B model	65
5.2.2 Equivalent parameters using the non-porous model	66
5.3 Equivalent Young’s modulus using the weighted average	67
5.4 Effect of different arrangement of piles on deformation	68
5.5 Summary	70
Chapter 6	CONCLUSIONS AND RECOMMEDATIONS	90
6.1 Conclusions	90
6.2 Recommendations for future work	92
REFERENCES	93
List of tables
Table 2.1 Factors affect soilcrete properties	12
Table 2.2 Compressive and tensile strength of the soilcrete	12
Table 2.3 E50/qu ratio of the soilcrete where original soil are from Taipei city	12
Table 2.4 Composite undrained shear strength prediction equation under axial applied load	13
Table 2.5 Composite undrained shear strength prediction equation under lateral applied load	14
Table 3.1 Loading condition for each type of tests	28
Table 3.2 The determination of the input parameters value	28
Table 3.3 The value of input parameters for composite soil	28
Table 4.1 Input parameters of soil layers used in the hypothetical case	50
Table 4.2 Input parameters of the soilcrete used in the hypothetical case	50
Table 4.3 Input parameters of structural elements used in the hypothetical case	50
Table 5.1 Input equivalent parameters using the MC-Undrained B model	71
Table 5.2 Input equivalent parameters using the non-porous model	71
Table 5.3 Input equivalent parameters using the MC-Undrained B model with the consideration of quincunx pile arrangement	71

List of figures
Figure 2.1 Typical pattern of improvement in excavation: (a) Block Type (b) Column Type (c) Wall Type (Wu, 1994)	15
Figure 2.2 Relation between Soilcrete unconfined compressive strength and different cement ratio (Chen, 1985)	15
Figure 2.3 Stress-strain curve of Soilcrete and clay (Wu, 1994)	16
Figure 2.4 Stress path comparison of real soil and Undrained A, Undrained B under Mohr-Coulomb model (Lim et al., 2015)	16
Figure 2.5 Evolution of principal stress rotation from different excavation stages (Lim& Ou, 2015)	16
Figure 2.6 Illustration of composite soil failure surface subjected to axial force (Lou, 2001)	17
Figure 2.7 Illustration of composite soil failure surface subjected to lateral force (Lou, 2001)	17
Figure 2.8 Illustration of composite material under axial loading (Yadama, 2007)  	18
Figure 2.9 Illustration of composite material under lateral loading (Yadama, 2007)	18
Figure 2.10 Cylinder geometry example for Halpin-Tsai’s notation	19
Figure 2.11 Comparison of Halpin-Tsai equation with Finite element analysis of normalized composite transverse stiffness (Circular fibers) (Halpin, 1969)	19
Figure 2.12 Comparison of Halpin-Tsai equation with Finite element analysis of transverse modulus of composite containing rectangular shape fiber (Halpin, 1969)	20
Figure 2.13 Relationship between m value and Ir under different qu (Wu 1994)	20
Figure 3.1 Arrangement of improvement piles (Wu, 2000)	29
Figure 3.2 Triaxial test simulation model for composite soil	30
Figure 3.3 Finite element mesh of composite soil	30
Figure 3.4 Loading condition for each type of tests	31
Figure 3.5 Equivalent Young’s modulus (Eeq) of composite soil model A for AC test)	32
Figure 3.6 Equivalent Young’s modulus (Eeq) of composite soil model B for AC test	32
Figure 3.7 Equivalent Young’s modulus (Eeq) of composite soil model C for AC test	33
Figure 3.8 Equivalent Young’s modulus (Eeq) of composite soil model D for AC test	33
Figure 3.9 Equivalent undrained shear strength (Su,eq) of composite soil model A for AC test	34
Figure 3.10 Equivalent undrained shear strength (Su,eq) of composite soil model B for AC test	34
Figure 3.11 Equivalent undrained shear strength (Su,eq) of composite soil model C for AC test	35
Figure 3.12 Equivalent undrained shear strength (Su,eq) of composite soil model D for AC test	35
Figure 3.13 Equivalent Poisson’s Ratio (νeq) of composite soil model A for AC test	36
Figure 3.14 Equivalent Poisson’s Ratio (νeq) of composite soil model B for AC test	36
Figure 3.15 Equivalent Poisson’s Ratio (νeq) of composite soil model C for AC test	37
Figure 3.16 Equivalent Poisson’s Ratio (νeq) of composite soil model D for AC test	37
Figure 3.17 Stress-strain curve of model A (Ir = 4%)	38
Figure 3.18 Plastic points and tension cut-off points of model A under the AC test (Ir=4%)	38
Figure 3.19 Evolution of Mohr circle	39
Figure 3.20 Evolution of Mohr circle with tension cut-off line	39
Figure 3.21 Illustration of soil strength and Mohr circle with tension cut-off line (ϕ=0)	40
Figure 3.22 Plastic points and tension cut-off points of model A under the AE test with plate element (Ir=4%)	40
Figure 3.23 Equivalent Young’s modulus (Eeq) of composite soil model A for LC test	41
Figure 3.24 Equivalent Young’s modulus (Eeq) of composite soil model B for LC test	41
Figure 3.25 Equivalent Young’s modulus (Eeq) of composite soil model C for LC test	42
Figure 3.26 Equivalent Young’s modulus (Eeq) of composite soil model D for LC test	42
Figure 3.27 Stress-Strain curve of model A with improvement ratio from Ir = 4 % to Ir = 64% for LC test	43
Figure 3.28 Plastic points and tension cut-off points of model A under the LC test (Ir=4%)	43
Figure 4.1 Plan of the excavation and layout of internal struts of Taipei Rebar Broadway case (Hsieh et al., 2008)	51
Figure 4.2 Subsoil profile and construction sequence of Taipei Rebar Broadway case (Lim, 2001)	51
Figure 4.3 Plan of the excavation and layout of internal struts of hypothetical excavation case	51
Figure 4.4 Finite element mesh of the hypothetical case	52
Figure 4.5 Top view of the hypothetical case	52
Figure 4.6 Profile of the hypothetical case with improvement piles (A-A cross section in Fig 4.4)	53
Figure 4.7 Plan of the excavation site and layout of improvement piles of the hypothetical case	53
Figure 4.8 Wall displacement and soil heave at first excavation stage with improvement ratio Ir = 0 ~ 44.44%	54
Figure 4.9 Wall displacement and soil heave at second excavation stage with improvement ratio Ir = 0 ~ 44.44%	54
Figure 4.10 Wall displacement and soil heave at third excavation stage with improvement ratio Ir = 0 ~ 44.44%	55
Figure 4.11 Wall displacement and soil heave at fourth excavation stage with improvement ratio Ir = 0 ~ 44.44%	55
Figure 4.12 Wall displacement and soil heave at final excavation stage with improvement ratio Ir = 0 ~ 44.44%	56
Figure 4.13 Relation between factor of safety and improvement ratio	56
Figure 4.14 Plastic points and tension cut-off points at (a) 1st (b) 2nd (c) 3rd excavation stage without ground improvement	57
Figure 4.15 Plastic points and tension cut-off points at (d) 4th (e) 5th excavation stage without ground improvement	58
Figure 4.16 Plastic points and tension cut-off points at (a) 1st (b) 2nd (c) 3rd excavation stage with Ir = 4%	59
Figure 4.17 Plastic points and tension cut-off points at (d) 4th (e) 5th excavation stage with Ir = 4 %	60
Figure 4.18 Plastic points and tension cut-off points at final excavation stage with Ir = 7.11 %	60
Figure 4.19 Plastic points and tension cut-off points at final excavation stage with Ir = 11.11 %	61
Figure 4.20 Plastic points and tension cut-off points at final excavation stage with Ir = 16 %	61
Figure 4.21 Plastic points and tension cut-off points at final excavation stage with Ir = 25 %	61
Figure 4.22 Plastic points and tension cut-off points at final excavation stage with Ir = 36 %	62
Figure 4.23 Plastic points and tension cut-off points at final excavation stage with Ir = 44.44 %	62
Figure 5.1 Finite element mesh for the 2D analysis	72
Figure 5.2 Wall displacement comparison from the 2D and the 3D analysis at five excavation stages	72
Figure 5.3 Finite element mesh for the 2D analysis with the EMS method	73
Figure 5.4 Illustration of the relation between the piles and the aspect ratios (side view)	73
Figure 5.5 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=4%)	74
Figure 5.6 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=7.11%)	74
Figure 5.7 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=11.11%)	75
Figure 5.8 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=16%)	75
Figure 5.9 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=25%)	76
Figure 5.10 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=36%)	76
Figure 5.11 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model (Ir=44.44%)	77
Figure 5.12 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model and the non-porous model (Ir=4%)	78
Figure 5.13 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model and the non-porous model (Ir=11.11%)	79
Figure 5.14 Comparison of wall displacement results between the RAS method and the EMS method using the MC-Undrained B model and the non-porous model (Ir=44.44%)	80
Figure 5.15 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=4%)	81
Figure 5.16 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=7.11%)	82
Figure 5.17 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=11.11%)	83
Figure 5.18 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=16%)	84
Figure 5.19 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=25%)	85
Figure 5.20 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=36%)	86
Figure 5.21 Comparison of wall displacement results between the RAS method and the EMS method using the Halpin-Tsai equation and the weighted average for Eeq (Ir=44.44%)	87
Figure 5.22 Relation between the maximum wall displacement ratio and improvement ratio with Eeq using the Halpin-Tsai equation and the weighted average	88
Figure 5.23 Plan of the excavation site and layout of improvement piles with quincunx arrangement	88
Figure 5.24 Comparison of wall displacement results with different pile arrangement under same improvement ratio (Ir≈11%)	89

                                

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