INVESTIGATING THE DYNAMIC MECHANICS OF SATURATED SOFT SANDSTONE USING ANISOTROPICALLY CONSOLIDATED CYCLIC TRIAXIAL TEST

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1 INVESTIGATING THE DYNAMIC MECHANICS OF SATURATED SOFT SANDSTONE USING ANISOTROPICALLY CONSOLIDATED CYCLIC TRIAXIAL TEST Der-Her Lee, Cheng-Jie Lia *, Jian-Hng Wu, Zha-Yu Ke 4, Chia-Ze Lai 4 ABSTRACT In anistrpic cnslidatin, the nrmal and shear stresses f a sample at the plane 45 frm hrizntal can be cntrlled by axial and cnfining stresses. Therefre, we carry ut anistrpic cnslidatin n Kuanmia sandstne and cnduct static and dynamic triaxial tests t evaluate the static and dynamic mechanism f saturated sft sandstne at the plane 45 frm hrizntal. In static triaxial tests, sft sandstne underges shear cntractin, indicated by the excess pre pressure generatin, then later turns t shear dilatatin since the pressure is then decreases t negative. The cyclic triaxial test results shw that the sample becmes unstable when excess pre pressure and axial strain starts t accumulate. The specimen prmptly fails when the axial strain reaches %, even when the stress state is still belw the static failure envelpe. Increasing the number f lad cycles t failure, N f, increases the accumulated displacement but decreases the shear mdulus, while the damping rati increases bviusly nce the sample appraches failure state. Key Wrds: Sft rck, Anistrpic cnslidatin, Shear mdulus, Damping rati INTRODUCTION There were many imprtant engineering prjects held next t the western fthills areas in recent years, such as tunnel excavatins, and highway bridges. Hwever, thse areas are mstly cnsisted f Negene clastic sedimentary rck with relatively shrt rck-frming perid, which prduces prus and prly cemented sft rck. The strength and cnslidatin prperties f sft rck are usually between sil and rck, making it unsuitable t be simply analyzed by therems regarding t sil r rdinary rck; thus, befre prceeding an engineering design in this area, we need first t understand the stress-strain behavir, mechanical prperties, and strength parameters f the sft rcks. Currently, numerus researches have been dne n sft rck in Taiwan with plenty f utcmes, such as A Study n the Relatinship f the Defrmatin Behavir and the Lithlgy f Tertiary Perid Sandstne by M.C. Weng, F.S. Jeng, T.H. Huang and L.S. Tsai (); and A Study n the Defrmatin Behavir f Mushan Frmatin Sandstne under Prfessr, Department f Civil Engineering, Natinal Cheng-Kung University, Tainan 7, Taiwan. Ph. D. Candidate, Department f Civil Engineering, Natinal Cheng-Kung University, Tainan 7, Taiwan. (*Crrespnding Authr; Tel.: #656; Fax: ; n6895@mail.ncku.edu.tw) Assciate Prfessrs, Department f Civil Engineering, Natinal Cheng-Kung University, Tainan 7, Taiwan. 4 Master, Department f Civil Engineering, Natinal Cheng-Kung University, Tainan 7, Taiwan

2 Different Stress Path by L.S. Tsai, F.S. Jeng and M.L. Lin (), which are mainly fcused n the defrmatin behavir f sandstne generated in the tertiary perid. Furthermre, C.A. Chen (994) has dne anther research n the mechanical behavir f Mushan sandstne under different stress path, when W.Y. Hsieh (995) did a research n the mechanical behavir f mudstne under varius temperatures and pressures. H.M. Lin, Y.F. Yu and C.J. Lia (4) studied the mechanical characteristics f Kuanmia sandstne. C.Y. Chang (998) and C.Z Su () separately investigate thrughly n the strain mechanism f sft sandstne frm Dakeng area in Taichung, and the in-situ mechanics and hydraulic prperties f sft rck f Tukshan frmatin at Hsinchu; and T.C. Ka () discussed the bearing behavir f pile driven in the sft rck. The active earth crust mvement arund Taiwan prduces a lt f earthquakes. Mst fault lines are distributed arund the western fthills and eastern Taiwan, and strng earthquakes culd induce disaster such as grund subsidence, sil liquefactin, slpe cllapse, landslide and debris flw, but despite f the thrugh researches regarding t the mechanical behavir f sft rck in Taiwan, the researches n dynamic behavir f sft rcks are still unppular. Thus, we will try t prceed dynamic triaxial tests t prbe the dynamic behavir f sft rck during earthquake. Samples f prus sft sandstne are taken frm Lngci in Tainan, and the labratry tests are mainly prceeded under anistrpic cnslidatin t simulate the initial stress cnditin f sft sandstne n the slpe. Dynamic lading is brught by shear stress path methd t prbe the dynamic behavir f saturated prus sft sandstne under earthquake. The stress path variatin f sft sandstne under dynamic lading and its vlume variatin in shear cnditin culd be calculated frm the excess pre pressure variatin. Besides, its shear mdulus and damping rati variatin under cyclic lading culd be fund by the thery f elasticity. THE CONCEPT OF ANISOTROPICALLY CONSOLIDATED DYNAMIC TRIAXIAL TEST Anistrpic cnslidatin By cnslidatin methd, dynamic triaxial test can be separated t be istrpically cnslidated and anistrpically cnslidated. The frmer is used t simulate sil layer under grund surface withut initial static shear stress (befre earthquake), and the latter is generally used t simulate sil layer with initial static shear stress n the failure surface f slpe r fundatin. In istrpic cnslidatin, the axial stress is similar t the cnfining stress. The specimen is evenly cnslidated at the plane 45 frm hrizntal withut initial shear stress. In anistrpic cnslidatin, the axial stress will be larger than the cnfining stress, and the initial static shear stress τ can be btained at the plane 45 frm hrizntal. The difference between the tw methds is displayed in Fig.. Usually, the cyclic shear-stress rati (Kc= / ) is used t determine the cnslidatin state f specimen. When Kc= the specimen is istrpically cnslidated, and when Kc> it is anistrpically cnslidated with initial static shear stress. The larger is the rati, the larger is the initial shear stress. Stress cntrl methd in dynamic triaxial test Because f the difficulty f test and the limitatin f apparatus in nrmal dynamic triaxial test, cnfining stress is usually preserved; while, axial stress is changed t simulate the effect f -455-

3 cyclic shear stress. As shwn in Fig.(a), cyclic shear stress Δτ=Δ d / is prduced at the plane 45 frm hrizntal when the cyclic axial stress Δ d is laded n the specimen, but the nrmal stress Δ d / which is simultaneusly prduced at the specified plane, which is different frm the actual cnditin. Therefre, t preserve the increase f cyclic shear stress Δτ at the plane 45 frm hrizntal but unchanged stress state in the nrmal directin, the cnfining stress will be cntrlled by server, which enable axial and cnfining stress t simultaneusly change t simulate the actual mechanical behavir f sil layer under cyclic shear stress. Fig.(b) shws the lading methd in the dynamic triaxial test in this research, which is similar t the stress cntrl methd fr ideal dynamic triaxial test mentined by Seed & Lee (996). = (a)nrmal dynamic triaxial test + Δ d (b)ideal dynamic triaxial test + Δ d 45 = = + = τ τ = 45 Fig. The stress cnditin f specimen in triaxial test under istrpic and anistrpic cnslidatin + Δ 45 d Δ τ = Δ d 45 + Δ d + Δ d Fig. The stress lading methd n nrmal and ideal dynamic triaxial test under istrpic cnslidatin Δ d Δ d Δ τ = Δ d Calculatin methd f stress cnditin In this research, dynamic triaxial tests are mainly anistrpically cnslidated t simulate the dynamic behavir f saturated prus sft sandstne slpe under earthquake, which will be shwn in Fig.. Fig.(a) is an unlimited slpe with ptential sliding surface at depth H. The initial nrmal stress and initial shear stress τ at the sliding surface are separately calculated by equatins () and (). Once the initial cnditin at ptential sliding surface is defined, we prceed anistrpic cnslidatin by adding different axial stress and cnfining stress t let the stress state at the plane 45 frm hrizntal similar t thse frmed at ptential sliding surface, where initial static shear stress exists. The magnitude f axial and cnfining stress can be calculated by the relatinship shwn in Fig.(b). Fig.(c) shws the axial and cnfining stresses laded t cylindric specimen, where cyclic shear-stress rati Kc can be calculated frm the relatinship f bth stresses. ' W cs θ = = [ γd( H Hw) + ( γsat γw) Hw] cs θ b () W sinθ csθ τ = = [ γd( H Hw) + γsathw] sinθcsθ b () Where: γ d γ sat H w is the dry unit weight f sft sandstne is the saturated unit weight f sft sandstne is the grundwater depth, and -456-

4 θ is the slpe angle b ' H W τ θ H w τ 45 ' + ' = τ = Fig. The stress cnditin design fr anistrpically cnslidated dynamic triaxial test Kc = TEST MATERIAL AND METHOD Test material The prus sft sandstne taken frm Lngci area in Tainan is investigated in this research. The gelgical map prpsed by W.P. Keng (98) shws that the rck belngs t the Kuanmia frmatin, which is cmparable t Tukshan frmatin in nrthern Taiwan. Kuanmia frmatin is integrated ver Nanhua mudstne, which mainly ranges frm lumpy fine sand t sandy quartzitic sandstne, with few alternatins f sandstne and mudstne. Its thickness is between 5m t m, which ften becme a syncline slpe alng its inclinatin angle. The lse structure is due t the shrt rck-frming perid, making it similar t silt r silty sand when it is disturbed r sftened by water. Fig.4 is the gelgical map drawn by the Natinal Gelgical Survey, MOEA, and the red dt in the figure shws the sampling area f this research, which is lcated at a slpe f cunty highway N.8 at.5k. Field investigatin shwed that the strike directin is N6E with dip angle between 6 t 4. The basic prperties f samples used in this research are shwn in Table, which were prus sft sandstne as shwn by vid rati e=.9. Hydraulic cnductivity k=5.9-5 (cm/sec) indicates gd permeability, and frm the aspect f slaking index Id =, which is classified as rck with very lw durability (Gamble, 97). Therefre, the slpe culd be sensitive t weathered and erded, which culd eventually lead t failure. Besides, water cntent is als an imprtant factr fr sft sandstne, where the uniaxial cmpressive strength fr saturated specimen decreases abut % f thse f dried specimen. Accrding t the results f uniaxial cmpressive strength, the Kuanmia frmatin sandstne is classified as sft rck(isrm, 98) Table Prperties f sft sandstne Prperties Value Field wet unit weight, γ t (kn/m ).5 Field water cntent, w(%) 9. Dry unit weight, γ d (kn/m ) 8.8 Specific gravity, G s.6 Vid rati, e.9 Grain-size distributin Sand, (%) 6 Silt, (%) 6 Clay, (%) Hydraulic cnductivity, k(cm/sec) Slaking Index, Id (%) Uniaxial cmpressive strength n air dried specimen, (MPa).98 Uniaxial cmpressive strength n saturated specimen, (MPa)

5 Fig. 4 The gelgical map f the hills area arund east side f Tainan (referred frm Natinal Gelgical Survey, MOEA) Test methd. Istrpically cnslidated - undrained static triaxial test Sft sandstne is easily lsen by water, thus, cylindric specimen will be made by pneumatic drill with the rati f length/diameter=.. The drilled specimen is placed int test apparatus and water is added t saturate the specimen and eliminate air bubbles. Cnslidatin step culd be started nce B value reaches.9, with previusly laded cnfining stress. Valves at the tp and bttm f apparatus are used as drainage path in cnslidatin prcess, and the cnslidatin is cmpleted when excess pre pressure decreases t zer r there is n mre vlume change in specimen. Valves will be clsed when the cnslidatin cmpletes, and axial stress in rate f.mm/min will be laded t prceed undrained static triaxial test. The variatin f stress-strain relatinship curve will be bserved, and lading shuld be stpped nce the deviatr stress and excess pre pressure becme static. The vlume change f specimen after test can be measured frm the recrd n vlume strain tube.. Anistrpically cnslidated - undrained static triaxial test Befre anistrpic cnslidatin is prceeded n the specimen, bth axial and cnfining stresses are laded t initial value t simulate the initial nrmal and shear stresses at the plane 45 frm hrizntal. Cnfining stress shuld be laded befre it is fllwed by axial stress, then the valves can be pened t prcess cnslidatin. Once excess pre pressure and vlume change f specimen are static, valves are clsed and the lading stage is started. This test will be cmpared t the dynamic triaxial test; therefre it will be perfrmed thrugh pure shear stress path. Rate f.5mpa/min is used t cnduct axial cmpressin and lateral extensin until the specimen fails.. Anistrpically cnslidated - undrained dynamic triaxial test This research aims t prbe the dynamic behavir f sft rck during earthquake, and it is cnducted under anistrpic cnslidatin t simulate initial stress cnditin f sft sandstne in a slpe. Cyclic lading f axial and cnfining stresses are cntrlled by server t prbe mechanical behavir and dynamic parameters variatin f specimen under pure cyclic shear stress, therefre, bth axial and cnfining stresses shuld be laded t initial value n saturated specimen t cnduct anistrpic cnslidatin and t simulate the initial nrmal and shear stresses at the plane 45 frm hrizntal. Once the cnslidatin finishes, valves are clsed t start cyclic lading with.hz sine wave. The angle between axial and cnfining stress is 8, and the cyclic lading cntinues until the specimen fails. Fig.5 shws the cyclic axial and cnfining stress used in this research

6 Axial stress Cnfining stress Fig. 5 Cyclic lading in the anistrpically cnslidated - undrained dynamic triaxial test TEST RESULTS AND DATA ANALYSIS Istrpically cnslidated - undrained static triaxial test Istrpically cnslidated undrained triaxial test is dne n prus sft rck specimen t understand its mechanical behavir under static lading, and the test is cmbined with different cnfining stresses t prbe its stress-strain relatinship. The shear behavir f specimen is acquainted frm excess pre pressure variatin. Fig.6 shws the stress-strain curve and excess pre pressure variatin curve f the istrpically cnslidated - undrained static triaxial test, frm which, we can see that specimen strength is increased alng with the increment f cnfining stress, but strain-sftening exhibits when the cnfining stress is lwer than MPa, and it is then ended with brittle failure. Frm excess pre pressure variatin curve, the specimen underges shear cntractin in initial shear stage with psitive excess pre pressure. Excess pre pressure reaches the maximum value when axial strain increased arund.5% t.8%, befre later turned t negative. At the same time, specimen underges shear dilatatin. Maximum negative value is reached when the specimen fails, and cntractin degree is raised alng with the increment f cnfining stress. 8 CU Test fr Kuan-Mia Sandstne 4 Undrained Ttal Stress Path Deviatr Stress, q=- (MPa) 6 4 c =.MPa c =.MPa c =.MPa (MPa) - q = p = + (MPa) Undrained Effective Stress Path Excess pre pressure u (MPa) Axial Strain, εa (%) Cmpressin Expansin Fig. 6 The stress-strain relatinship and excess pre pressure variatin curve f the istrpically cnslidated - undrained static triaxial test q = ' -' (MPa) 4 6 ' +' p' = (MPa) Fig. 7 Ttal stress path and effective stress path f the istrpically cnslidated - undrained static triaxial test Frm the effective stress path (Fig.7), the effective stress rises cntinuusly nce the specimen is sheared, and after it reaches maximum value, the specimen fails and the effective

7 stress decreases t the residual cnditin. Shear dilatatin is bvius when the cnfining stress is under MPa, which is similar t the behavir f dense sand. Regressin line equatin as shwn in Fig.7 is btained by regressing the peak and residual stresses. Table shws the shear strength parameters in Mhr-Culmb failure criterinτ=c+tanψ which is btained by prceeding linear regressin ver Mhr stress circle drawn by the test results. Table Shear strength parameters btained frm the istrpically cnslidated - undrained static triaxial test Cnfining stress, ' C c p φp cr φ c' r p p c' r r (MPa) (MPa) ( ) (MPa) ( ) (MPa) ( ) (MPa) ( ) Anistrpically cnslidated - undrained static triaxial test Anistrpic cnslidatin is prceeded n rck specimen t prduce initial shear stress at the plane 45 frm hrizntal t simulate the initial stress cnditin f the sft sandstne slpe t prbe its stress-strain behavir, excess pre pressure and effective stress path under pure shear stress. In the terms f cnslidatin stress, assume the slpe is 45 m high with inclinatin, with grundwater lcated 9.5m belw grund surface, which result in initial nrmal stress =.65MPa and initial shear stress τ =.4MPa, s the cnslidatin is prceded with =.5MPa and =.5MPa. Once the cnslidatin finishes, the test will be prceeded with rate f.5mpa/min. Excess Pre Water Pressure u (MPa) Deviatr Stress, ( - ) (MPa) Undrained Triaxial Test fr Kuan-Mia Sandstne =.5 MPa, =.5 MPa B-Value = 9. % Stress Rate =.5 MPa/min Axial Strain, ε a(%) Axial Strain, ε a(%) Fig. 8 The stress-strain relatinship and excess pre pressure variatin curve f the anistrpically cnslidated - undrained static triaxial test (MPa) q = - (MPa) q = ' -' Undrained Ttal Stress Path 4 Undrained Effective Stress Path CU test (disp. cntrl) =. (MPa) CU test (stress cntrl) =.5 (MPa), =.5 (MPa) p = + (MPa) CU test (disp. cntrl) =. (MPa) CU test (stress cntrl) =.5 (MPa), =.5 (MPa) 4 p' = ' +' (MPa) Y =.49X +.75 Y =.54X +.67 Y =.55X +.67 Y =.567X +.6 Fig. 9 Stress path f the undrained static triaxial test (cmparisn between istrpic and anistrpic cnslidatin) Fig.8 shws the stress-strain curve and excess pre pressure variatin curve btained by the test, frm which the strain-sftening exists and the failure mde is brittle. Excess pre pressure cntinues t accumulate in negative value alng with the increment f axial strain befre later becme stable. In Fig.9 we cmpare the stress path f this test with the cnfining stress.mpa in istrpically cnslidated test. The ttal stress path in anistrpic cnslidatin has already failed when it appraches t the failure line, while the residual stress appraches the residual line. The effective stress path f the test is almst reduplicating thse f istrpically cnslidated, where it has als failed when it appraches the failure line -46-

8 and eventually decreases the effective stress. This is expected t be caused by partial cracks n specimen prduced when the axial stress is larger than cnfining stress in anistrpic cnslidatin prcess. Anistrpically cnslidated - undrained dynamic triaxial test Anistrpically cnslidated dynamic triaxial test is prceeded t prbe the dynamic behavir f prus saturated sft sandstne slpe during an earthquake, where cyclic lading f axial and cnfining stresses are cntrlled t maintain the pure shear stress cnditin. Dynamic behavir is acquainted by measuring the variatin f excess pre pressure and axial strain. At the same time, the variatin f dynamic parameters can be acquainted by calculating the relatinship f shear mdulus G and damping rati D with the number f lad cycles. Table The results f the anistrpically cnslidated - undrained dynamic triaxial test Water Specimen N. cntent K ' τ a τcyc c (%) (kpa) (kpa) (kpa) (kpa) (kpa) D u max b (kpa) D D a) Cyclic shear stress b) Maximum excess pre pressure c) Lad cycles t failure Principal stress (kpa) Excess pre water pressure (kpa) 5 5 (a)τcyc=7kpa (b)τcyc=4kpa (c)τcyc=kpa Minr principal stress Excess pre water pressure Majr principal stress Principal stress (kpa) Excess pre water pressure (kpa) 5 5 Minr principal stress Majr principal stress Excess pre water pressure -6 4 Principal stress (kpa) Excess pre water pressure (kpa) 5 5 N f c Minr principal stress Majr principal stress Excess pre water pressure Axial strain (%) Axial strain εa=.8% Axial strain (%) Axial strain εa=.% Axial strain (%) Axial strain εa=.9% Time (sec) 4 Time (sec) Fig. The results f the anistrpically cnslidated - undrained dynamic triaxial test (Kc=4.) Time (sec) Anistrpic cnslidatin is again prceeded with =.5MPa and =.5MPa (Kc=4.). The cyclic lading is prceeded under.hz sine wave. Table and Fig. shw the results f the anistrpically cnslidated - undrained dynamic triaxial test. There is bvius accumulatin f excess pre pressure befre failure, which decreases the effective stress f specimen and gradually increases the axial strain, and the specimen prmptly fails nce the axial strain is arund %. Accumulated excess pre pressure is increased alng with the increment f cyclic shear stress. By bserving the variatin f axial strain, excess pressure accumulatin is separated int -46-

9 stages. Accelerated accumulatin in the first stage is fllwed by the stable secnd stage, while the rapid increment in third stage starts when there is bvius accumulatin f the excess pre pressure. This shws the bvius influence f excess pre pressure accumulatin t sft sandstne, since the effective stress decreases and axial strain increase cntinuusly nce the excess pre pressure is bviusly accumulated. Dynamic parameters variatin T prbe the dynamic parameters variatin f prus saturated sft sandstne under cyclic lading, the lp f number f cycles in each stress-strain variatin curves is calculated t btain the variatin f shear mdulus G and damping rati D. Elastic mdulus needs t be fund befre calculating the shear mdulus by the thery f elasticity such as shwn in equatin (). Damping rati is calculated by Kelvin-Vigt mdel, which relatinship with lp cycle is shwn in Fig.; and the damping rati f each lp can be btained by equatin (4). In which, W indicates the energy lst during each lp, and W is the maximum strain energy stred within an bject. G = E/( + υ) () D ΔW 4π W = (4) Fig. shws the relatinship between shear mdulus and the number f cycles, frm where the initial shear mdulus G increases tgether with the number f cycles N, which happens since the initial cyclic lading presses the vid inside prus sft sandstne and makes it denser, but excess pre pressure accumulates under cyclic shear stress which slwly destrys the cementatin f the rck, which rapidly decreases the shear mdulus G when the sample fails. Fig. shws the relatinship between damping rati and the number f cycles, frm where the damping rati tends t decrease until it becmes stable alng with the increment f the number f cycles, but then cntrarily increases when the sample appraches t failure, which happens since the energy lst when the specimen is sftening due t cyclic lading cntinues t increase. The damping rati increases, then rapidly defrms. 8 5 F,τ ΔW D = 4π W ur, Shear mdulus, G (MPa) τcyc=7kpa τcyc=4kpa τcyc=kpa Damping rati(%) 4 τcyc=7kpa τcyc=4kpa τcyc=kpa 6 Nmber f cycles, N Nmber f cycles, N Fig. The relatinship f lp cycle and damping rati Fig. The relatinship between shear mdulus and the number f cycles Fig. The relatinship between damping rati and the number f cycles CONCLUSIONS -46-

10 Frm the excess pre pressure variatin under cnfining stress between. and.mpa in istrpically cnslidated undrained static triaxial test, the sft sandstne underges shear cntractin in the initial shear stage, but turns t shear dilatatin when the excess pre pressure reaches maximum value. The maximum negative value f excess pre pressure is apprached when the deviatr stress is maximized, and, at the same time, the shear dilatatin degree f specimen is als maximized. The result f anistrpically cnslidated undrained dynamic triaxial test f saturated Kuanmia sandstne shws bvius accumulatin f excess pre pressure which decreases the effective stress f specimen befre it fails under cyclic shear stress when the accumulated strain is arund %, with failure surface prduced arund 45 t 6 frm hrizntal. The dynamic parameters variatin shws that shear mdulus f sft sandstne bviusly decreases when it appraches t failure, while damping rati tends t be stable befre increases in the end. Thus, the failure surface f saturated sft sandstne slpe during earthquake is influenced by cyclic shear stress. Accumulated excess pre pressure decreases the effective stress and destabilizes the slpe. Decreasing shear mdulus and increasing damping rati eventually result in slpe failure. REFERENCES Chang, C.Y.(998). The Strain Behavir f Sft Sandstne, M.Sc thesis, Natinal Chia Tung University. (in Chinese) Chen, C.A.(994). A Study f the Characteristics f Quartzitic Sandstne under Different Stress Path, M.Sc thesis, Natinal Cheng Kung University. (in Chinese) Gamble, J.C.(97). Durability-Plasticity Classificatin f Shales and Other Argillaceus Rcks, Ph. D. thesis, University f Illinis. Hsieh, W.Y.(995). Mechanical Behavirs f Mudstne at Elevated Temperatures and Pressures, M.Sc thesis, Natinal Cheng Kung University. (in Chinese) ISRM,(98) Basic getechnical descriptin f rck masses, ISRM Cmmissin n Classificatin f Rcks and Rck Masses. Int. J. Rck Mech. Min. Sci. & Gemech. Abstr. Vl. 8, pp.85-. Ka, T.C.(). A Study f the Bearing Behavir f Pile Driven in Sft Rck with Pile Lad Testing, M.Sc thesis, Natinal Central University. (in Chinese) Keng, W.P.(98). The Gelgy f Hills Area in East f Tainan, Natinal Gelgical Survey Jurnal, MOEA, first editin, -. (in Chinese) Lin, H.M., Y, Y.F., and Lia, C.J.(4). A Study f the Mechanical Behavir f Kuanmia Sandstne, 4 Taiwan Rck Engineering Sympsium Jurnal, 6-4. (in Chinese) Seed, H.B., and Lee, K.L.(966). Liquefactin f Saturated Sands during Cyclic Lading, Jurnal f the Getechnical Engineering Divisin, ASCE, 9(6), 5-4. Su, C.Z.(). Pressuremeter, Lugen and P-S Lgging Tests in Lw Strength Rcks, M.Sc thesis, Natinal Chia Tung University. (in Chinese) Tsai, L.S., Jeng, F.S., and Lin, M.L.(). A Study n the Defrmatin Behavir f Mushan Frmatin Sandstne under Different Stress Path, 9th Getechnical Cnference Jurnal, B. (in Chinese) Weng, M.C., Jeng, F.S., Huang, T.H., and Tsai, L.S.(). A Study n the Relatinship f the Defrmatin Behavir and the Lithlgy f Tertiary Perid Sandstne, 9th Getechnical Cnference Jurnal, B. (in Chinese) -46-