Utilization of weathered rock mass as the China Three Gorges Project Dam foundation

Transcription

1 Innov. Infrastruct. Solut. (2017) 2:51 DOI /s TECHNICAL NOTE Utilization of weathered rock mass as the China Three Gorges Project Dam foundation Shirong Xiao 1 Guodong Zhang 1 Qingjun Zuo 1 Received: 27 June 2017 / Accepted: 31 July 2017 / Published online: 15 August 2017 Ó Springer International Publishing AG 2017 Abstract The utilization of the weathered rock mass in the Three Gorges Dam Area is one of the key geotechnical issues for the China Three Gorges Project (CTGP) construction. Engineering geological investigations and tests had been carried out to study the physical, chemical, mineral and mechanical properties and distribution characteristics in detail for more than 30 years. The classification of the weathered zone has been further divided. The utilization of the lower part of the weakly weathered zone as the Three Gorges dam foundation rock mass had been researched by consolidation grouting test. The research results show that: (1) the weathered crust rock mass in China Three Gorges Dam Area has a thickness of m, with four different weathering state rock as loose, half loose, half hard and hard and four different weathered zones as complete, intense, weak and light. (2) It was feasible that the lower part of the weakly weathered zone could be used as the dam foundation after consolidation grouting treatment. (3) It has set a rock mass quality evaluation criterion with CTGP characteristic to access the foundation rock mass quality Three Gorges YZP Method. (4) The CTGP practice shows that it is successful for the utilization of the lower part of the weakly weathered rock mass as the dam foundation, saving a This paper was selected from GeoMEast 2017 Sustainable Civil Infrastructures: Innovative Infrastructure Geotechnology. & Shirong Xiao @qq.com Guodong Zhang zgd@ctgu.edu.cn Qingjun Zuo @qq.com 1 College of Civil Engineering and Architecture, China Three Gorges University, 8#, Daxue Road, Yichang , Hubei, China large amount of construction investment and shortening a certain amount of construction time for the CTGP. Keywords Weathered rock mass Rock mass quality Dam foundation China Three Gorges Project Introduction The engineering utilization of weathered rock mass at crystalline rock engineering area is related to quality, duration and cost of a project. Therefore, it has always been a key geotechnical issue focused by academic and engineering [1 4]. The bedrock of the China Three Gorges Project dam site (Fig. 1) is granite with crystalline texture, massive structure and the thickness of weathered crust more than 40 m. Influenced by the topography, geomorphology and geological structure, the properties of weathered crust varies greatly [5]. However, it shows that the weathering intensity gradually weakens from the mountain top to bottom, and it is divided into four zones such as completely weathered zone, intensely weathered zone, weakly weathered zone and slightly weathered zone. Thus, the selection of the dam foundation rock mass and the utilization of the weathered crust are the important engineering geological issues for the CTGP and have great meaning both economically and technically [6]. The CTGP construction practice shows that it is successful for the utilization of the lower part of the weakly weathered rock mass as the dam foundation, saving a large amount of construction investment and shortening a certain amount of construction time for the Three Gorges Project. This paper summarizes the process and results of the survey and experimental study on the engineering utilization of the lower part of the weakly weathered rock mass as the Three Gorges Dam foundation.

2 51 Page 2 of 10 Innov. Infrastruct. Solut. (2017) 2:51 Fig. 1 Sketch map of the layout of CTGP Weathered crust classification and the main engineering geological characteristics of crystalline rock In the long geologic time, suffering from the effect of various kinds of weathering agent [7], the bedrock of TGP dam site appears inhomogeneous on the macro, and has a rather thick weathered crust containing four kinds of different weathering state rock such as loose, half loose, half hard, hard (Table 1; Fig. 2), and divides four weathered zones regularly and orderly, complete, intense, weak and light from the outside to the inside of the section (Figs. 2, 3). Due to different weathering intensity in different weathered zones [8], it shows different comprehensive characteristics in terms of the combination of weathered rock mass, rock mass structure and integrity, physical and mechanical properties and hydro-geological features. Therefore, it forms the basis of weathered crust classification [9, 10]. Completely weathered zone (IV) The composition is almost loose and half-loose rock, the content of which is more than 95%. It mixes up with a little fragment stone, with some hard weathered block with round shape distributed sporadically on the bottom. The rock has largely lost crystalline connection. Generally speaking, the quality of rock is more homogeneous with loose structure, low strength. The rebound index is about 10, and the compressive strength in saturation is less than 10 MPa. Intensely weathered zone (III) The composition is partly loose to half-loose rock, mixing up with hard and half-hard rock, and the loose to half-loose rock makes up 30 70%. Among the rock mass, weathered block with round shape of hard and half-hard rock is surrounded by loose and half-loose rock mass. The number of weathered block with round shape is increasing from the top to the bottom. The whole connection force and strength character are almost equal to the rock mass of completely weathered zone. The permeability of the rock mass is strong in intensely weathered zone, whose permeability coefficient is m/day, and some part reaches 11 m/day. Then V p is generally m/s, the minimum of which only reaches 500 m/s. The rebound index is 10 31, average value reaching 19.6; the compressive strength in saturation is less than 20 MPa. Table 1 Physical and mechanical parameters of different weathering state rocks Weathered rock category Unit weight (kn/m 3 ) Water absorption (%) Porosity (%) V p (m/s) Rebound index Deformation modulus (GPa) Compressive strength (MPa) Loose Half loose (dry) Half hard (wet) Hard [ [100 (wet)

3 Innov. Infrastruct. Solut. (2017) 2:51 Page 3 of Fig. 2 The different weathering state rocks and weathered zones. a IV zone (loose rock), III zone (half loose rock and half-hard rock). b II 2 subzone (half loose rock and hard rock, sandwich and cataclastic structure); II 1 (hard rock, sub-block structure). c II 1 (hard rock, sub-block structure), I (hard rock, block structure). d II 1 (hard rock, soft debris interlayer, sandwich structure) Weakly weathered zone (II) Exposed by a large number of boreholes, heavy-caliber and minor-caliber drilling, and through physical and mechanical parameters tests, it fully shows that the weakly weathered zone can be divided into two subzones, the upper zone and the lower zone, and there appears obviously different engineering geologic features between the two subzones. Upper weakly weathered zone (II 2 ) It is composed of hard to half-hard rock, mixed up with loose to half-loose clasts, which occupies 9 20% and reaches 30% at maximum, mainly filling in the structural plane. It results in the junction thickening, and 30 70% of the structural plane contains clasts, whose thickness is m and the thickest are up to m. The rock mass is dominating weathering along fractures with much inhomogenous rock mass quality. The structure type belongs to cataclastic-sub-massive structure, and the integrity of rock mass is medium to poor, appearing very inhomogenous, and the thickness is 2 4 m. Lower weakly weathered zone (II 1 ) The main composition is hard rock, mixed up with a little loose to half-loose rock mass. Among these rock mass, the thickness of the loose and half-loose rock mainly are several millimeters and a few reach 1 4 cm, most distributing in structure plane with steep dip angle. The rock mass quality and the engineering geological features of this zone is more homogeneous, with the compressive strength in saturation being MPa, modulus of deformation being (20 30) MPa, and the rebound index reaching 41. Slightly weathered zone (I) It is made up of hard rock with highly slight weathering. Only along part of fissure surfaces appeared phenomenon of yellow rust or the weathering skin about 1 mm, and a few structural planes were weathered more serious. The hard filling things occupied 5%, the soften plane occupied 1 2%. The behavior of the rock mass in the slightly weathered zone is similar to the fresh rock mass, with good quality and weak permeability. The compressive strength in saturation R c is more than 100 MPa and the value of modulus of deformation is (30 40) MPa. The rebound index value is 46.4 and the V p is generally 5.39 km/s, the maximum of which can reach 6 km/s. On the whole, the rock mass is homogeneous, complete, with superior engineering geological properties. The total thickness of the weathered crust is increasing gradually from the river bed to the mountain ridge (seen in Fig. 4). The maximum of thickness of the weathered crust composed of completely, intensely, weakly weathered zone in the river bed is m and the average is m; the maximum of in the floodplain is m and the average is m; the maximum of in the terrace is m and the average is m; the maximum of in the valley is m and the average is m; the maximum of in the hillside is m and the average is m; the maximum of in the ridge is m and the average is m.

4 51 Page 4 of 10 Innov. Infrastruct. Solut. (2017) 2:51 Fig. 3 Sketch of weathered profile in the dam site of CTGP The possibility of using weakly weathered rock mass as dam foundation Different opinions for choosing the Three Gorges Dam foundation rock The several geotechnical investigation reports that had been submitted by Ministry of Geology and Mineral Resources and Changjiang Water Resources Commission (CWRC) put forward the idea of choosing the slightly weathered zone rock mass as the dam foundation. The specialists in the area of geology, rock mechanics, and hydraulic engineering also agreed with the opinions from the exploration units. The consulting group of rock mechanics and foundation design, which was composed of the expert Anderson of rock mechanics test from the US Bureau of Reclamation and the Army Corps of Engineers, the experts of engineering

5 Innov. Infrastruct. Solut. (2017) 2:51 Page 5 of Fig. 4 Column diagram of weathered crust distribution versus landform geology and the experts of dam foundation design, came to China to consult and investigated in the construction site. The USA expert thought that it was best for the Three Gorges Dam to set up on the rock mass of slightly weathered zone. The upper rock mass of the weakly weathered zone could not be used. Only with less load condition and after the rock mass consolidated, it has the possibility to make use of the lower part of the weakly weathered zone. However, it was better not to use it for the importance of the Three Gorges Project. Because the interface is uneven between the upper part and the lower part, while the lower part was used, the upper part might be left over, which is harmful to the dam foundation stability, and it leads to a waste of money. It is better to dig it up first. In the 70s, the Institute of Three Gorges Survey and investigation from CWRC carried out investigation research on the use of weakly weathered zone rock mass at the Tai Pingxi dam site (comparative dam site). According to the information about the geologic description of footrill, small-diameter diamond drilling and acoustic wave test, the weakly weathered zone was divided into two subzones: the upper zone and the lower zone. The use of the lower weakly weathered zone was emphatically studied, taking grouting tests, the large deformation tests and acoustic wave tests at 5# adit. In the late 70s, the survey and experimental study on the use of the weakly weathered rock mass were kept on after paying attention to the San Douping dam site (Three Gorges Dam site). The research resulted that the engineering geological properties of the lower rock mass in the weakly weathered zone was similar to the rock mass in the slightly weathered zone having the possibility of choosing as the dam foundation. Doctor Campbell, a Canadian expert, from the World Bank Group, insisted on the weakly weathered zone as the foundation base, as well as the opinion of the Doctor Muller. They thought that the loose and cracked rock mass was partial, especially the upper part, surrounded by intact rock mass. It could be treated by excavating like the dental operation. The whole rock mass in the weakly weathered zone could satisfy the requirement of the dam foundation after grouting. Tackling key research on the possibility of use of the weakly weathered rock mass For the possibility of using the rock mass in weakly weathered zone, it had been researched and argued in depth from the seven fields: rock mass engineering geological features, rock mass properties, classification and evaluation of rock mass quality, numerical analysis and stability evaluation for different rock plane of dam foundation and the test result of the strengthening. The main conclusions are summarized as follows. Taking consideration of the overall characteristics and conditions of lower weakly weathered rock mass, it was superior to the upper weakly weatheredrockmassasthe Three Gorges Dam foundation. It was similar to the slightly weathered rock mass, and it does not have the problem such as foundation sliding along the superficial zone, uneven bearing, deformation and seepage stability. Therefore, the lower weakly weathered rock mass can be used for the project completely, and its characteristic and condition would be better after proper reinforcement. However, the geological flaw, with respect to the lower weakly weathered rock mass on its heterogeneity, was obvious. The loose debris sandwich, whose thickness was 5 20 cm, is difficult to handle. There exists security and stability problem that cannot satisfy the engineering requirement. Therefore, first, it was needed to set up a

6 51 Page 6 of 10 Innov. Infrastruct. Solut. (2017) 2:51 dam foundation rock mass evaluation criterion and system to assess the rock mass quality, and second, it was needed to carry out an experimental study on weathered rock mass reinforcement. The establishment of TGP Dam foundation rock mass quality criteria: Three Gorges YZP Method Evaluation of dam foundation rock mass quality was carried out based on geological analysis and rock mass parameter tests, among which the weathered rock mass classification and rock mass structure classification are the more important bases. Based on the Barton Q method and Bieniawski RMR method, the Three Gorges YZP Method (seen in Fig. 5) determines the rock mass quality coefficient M by weighted averaging the following five factors of rock mass such as integrity (U 1 ), rock strength (U 2 ), discontinuity situation (U 3 ), permeability (U 4 ), and deformation (U 5 ). The function formula and the weighted averaging model are as follows: M ¼ f ðu 1 ; U 2 ; U 3 ; U 4 ; U 5 Þ; M ¼ Xn i¼1 W i S i ; S i ¼ x i : x imax In above equations, S i refers to proportionality coefficient, x i stands for the parameter value of No. I factor, and x max is the biggest factor value, W i is the weight value of No. I factor, which satisfies P n i¼1 W i ¼ 1. Derived from experience assessment and calculation results, it was determined that W = [0.3, 0.25, 0.2, 0.1, 0.15]. Changing the M value to score M s gives the below equation: " # M S ¼ Xn ðw i S i Þ 100: i¼1 It obtained the rock mass quality score from above formula as seen in Table 2. The quality of TGP Dam foundation rock mass is classified into five grades as below: Grade A (excellent rock mass): M s C 85, fresh and slighted rock mass with massive and block structure, excellent dam foundation rock mass. Grade B (good rock mass): M s = 70 85, including fresh and slighted rock mass with sub-block structure, lower weakly weathered rock mass with block structure, good dam foundation rock mass after being treated by common engineering methods. Grade C (middle quality rock mass): M s = 45 70, including well-cemented hard tectonite, cataclastic structure rock mass, and the up weakly weathered zone with sub-integrity structure. It will only be well treated and consolidated; the middle quality rock mass could be selected as the dam foundation rock mass. Grade D (bad quality rock mass): M s = 25 45, including soft tectonite with cataclastic structure rock mass, and the up weakly weathered zone with thick sandwich structure. It could not be used for the dam foundation. Grade E (very bad quality rock mass): M s \ 25, including intensive fractured and soft tectonite with montmorillonite, and the completely, intensively weathered zones. It could not be used for the dam foundation. The Three Gorges YZP Method is suitable and better for the TGP Dam foundation rock mass quality evaluation, compared to the Barton Q method and Bieniawski RMR method (seen in Table 3). The evaluation result from the Three Gorges YZP Method is close to that of Barton Q method, while almost one grade higher than of the Bieniawski RMR method. The experimental study on weathered rock reinforcement To study the effect of the rock consolidation grouting test to the upper and lower weakly weathered rock mass, the Yangtze River Academy and the Institute of Three Gorges Fig. 5 Evaluation factors and system of Three Gorges YZP Method Rock mass integrity Rock compress strength A excellent B good Three Gorges YZP Method Discontinuity character Rock mass permeability Rock mass deformation C middle D bad E very bad

7 Innov. Infrastruct. Solut. (2017) 2:51 Page 7 of Table 2 Three Gorges YZP Method Q evaluation in detail Q classification Rock mass Acoustic wave V p (km/s) Integrity K v RQD (%) Compressive strength R c (MPa) Permeability % Deformation index E d (GPa) M (Q index) A I and fresh Slight permeable B II Weak permeability C D II Middleintense permeability D E Cataclastic rock mass Tectonic soft rock mass Middleintense permeability [ \3 \2.5 \20 \ \25 Table 3 Comparison for different rock mass Q evaluation methods Q Rock Mass Structure Integrity and block Block Subblock Mozaic Cataclastic loose Cataclastic Cataclastic Loose Barton Q Fresh, ; slightly, Bieniawski RMR Fresh, 85 92; slightly, Three Gorges YZP method M Fresh, 95.9; slightly, / , lower , up weakly II 1 weakly II , soft tectonite 0.022, intensive 69 71, lower , up , weakly II 1 weakly II 2 intensive , lower , up weakly II 1 weakly II 2 Survey and investigation from CWRC chose three test areas at 5# adit in the Tai Pingxi dam site in Thereinto, II and III test areas were located in the upper rock mass of the weakly weathered zone (I test area reserved for comparison), and IV test area was located in lower rock mass. The three test areas, respectively, adopted three different materials, cement, epoxy resin and polymethyl, to carry out grouting tests. II test area It is the quartz diorite on the upper weakly weathered zone, with passing through six faults, so the rock mass integrity is poor. It was arranged 24 grout holes in this area using the ring oxygen resin grouting, starting the experimental grain filling after high-pressure water washing. Because of the lack of the slurry material, only six grout holes with location dispersing were filled with grain. The maximum single-hole grouting pressure reached 0.2 MPa, the minimum less than 0.01 MPa, and the typical value was MPa. The maximum single-hole grouting-absorption capacity reached 116 L, the typical value being about 40 L and the total was 424 L. III test area It is the quartz diorite on the upper weakly weathered zone, with many fractures of mediumand low-angle dip. It was deployed with 22 grout holes using Portland cement at the area. The maximum grouting pressure reached 0.8 MPa, the minimum being 0.02 MPa, and the maximum single-hole grouting-absorption capacity reached 955 L/min. The total cement consumption was 1531 kg and unit consumption was kg. IV test area It was a quartz diorite black diorite rock in the lower part of the weakly weathered zone, with three small faults whose width was 5 10 cm, fissure ratio about 0.5%. It was layout 22 grouting holes in this area with polymethyl methacrylate casting material. Because of the lack of slurry material, 13 grout holes with dispersing location were filled with grain. The maximum single-hole grouting pressure reached 0.6 MPa, and the typical value was MPa. The maximum single-hole grouting-absorption capacity reached 58.9 L, the typical value being about 7 40 L and the total was L. Both took water pressure test before and after grouting, and the changes of their specific water absorption (x) are shown in Table 4.

8 51 Page 8 of 10 Innov. Infrastruct. Solut. (2017) 2:51 Table 4 Comparative list of the specific water absorption before and after grouting Test area The specific water absorption before and after grouting x (L min -1 m -1 m -1 ) Pressure (MPa) Native state (x) After the grouting (x 0 ) x x 0 x II III IV Table 5 Comparative table of the modulus of deformation and elasticity modulus before and after grouting Test area Test method Modulus of deformation Elasticity modulus E 1 E 2 E 1 E 2 E 1 E 0 1 E 0 2 E 0 1 E0 2 E 0 1 II Flexibility Stiffness III Flexibility Stiffness IV Flexibility Stiffness Table 6 Comparative table of the wave velocity and the dynamic elastic modulus before and after grouting Test area Average wave velocity V p (km s -1 ) Dynamic elasticity modulus (910 3 MPa) Effect Native state After washing After grouting E d E 0 d I II III IV x¼ Ed E0 d E d 100% Elastic modulus and deformation modulus tests were carried out on the spot before and after grouting, and the results are shown in Table 5. All grouting holes were taken for ultrasonic test; the wave velocity changes before and after grouting and the dynamic elasticity modulus rock mass are shown in Table 6. Through consolidation grouting test and comparative analysis, the following elementary opinions were concluded. Lower part of the weakly weathered rock mass (IV test area) was with better homogeneity and integrity, and each index was enhanced than before. After consolidation grouting treatment, the deformation modulus and elastic modulus increased significantly, with obvious low permeability, longitudinal wave velocity increase, and the integrity of rock mass had been improved. The lower part rock mass quality enhanced from grade B to grade A. Therefore, the lower part rock mass can be as the Three Gorges Dam foundation after consolidation grouting treatment. Upper part of the weakly weathered rock mass (II, III test area) is weathered intensively along the fractures and fault zones, with more inhomogeneous and less integrity. Through consolidation grouting treatment, the water permeability reduced obviously, with the deformation modulus and elastic modulus enhanced, and the rock mass behavior improved. However, due to so much loosened-tohalf-loosened debris distributing along the fractures and fault zones, it was unable to wash clean the loosened-tohalf-loosened debris and the consolidation effect was not obvious. It was difficult to reach grade A by consolidation grouting. Thus, it cannot satisfy the fundamental demand of the dam. The anti-sliding stability evaluation for lower weakly weathered rock mass as foundation base The calculation condition 1. Chose the 5# unit on the left dam sections as a typical geological section of the dam (seen in Fig. 6), and took lower part of the weakly weathered rock mass as dam foundation and its surface elevation 90 m. Then the

9 Innov. Infrastruct. Solut. (2017) 2:51 Page 9 of When selecting parameters: f ¼ 1:2; c ¼ 1:5 MPa; K 0 ¼ 5:68 f ¼ 1:0; c ¼ 1:5MPa; K 0 ¼ 5:22: The calculations show that the safety factor against sliding K 0 was greater than 3. Therefore, the performance can meet the engineering requirements of stability against sliding using the lower weakly weathered zone rock mass as the dam foundation. Fig. 6 The excavation image of left 1 5# dam and power house elevation of the dam crest was 185 m, designing reservoir level being 175 m in the upstream, and the water level was 66 m in the downstream. The calculation model is seen in Fig Took two sets of parameters to calculate, one with the shear strength of concrete and the other with bedrock at the bottom of the weakly weathered rock mass: f = 1.2, c = 1.5 MP or f = 1.0, c = 1.5 MPa. 3. Calculation load: the upstream water pressure P H = 1/ 2rH 2 = t, the weight of the dam concrete W = t, the upstream silt pressure force P n = 1/ 4h 2 n = 25 t, the uplift coefficient a = 0.25, the uplift pressure U = U 1? U 2 = 1267 t. The calculation results and evaluation Adopting shear-friction formula: f ðw UÞþC L K 0 ¼ : P H þ P n The TGP Dam foundation rock mass quality detection and the achievements of utilization of the weathered rock mass as the dam foundation The TGP Dam foundation rock mass quality detection The TGP Dam foundation rock mass quality detection practice was carried out by borehole test and acoustic wave detection [11]. The dictation practice, deploying about 1 borehole/ m 2, mainly included geological check, acoustic wave test, permeability test and taking samples for lab mechanical test. The detection results are summarized as below: 1. The dam foundation rock mass quality is above grade A, satisfying the design requirement. 2. The average RQD of lower part of weakly weathered rock mass is above 70%. 3. The average V p of lower part of weakly weathered rock mass exceeds 5 km/s. Fig. 7 The stability calculation model of left 1 5# dam and power house

10 51 Page 10 of 10 Innov. Infrastruct. Solut. (2017) 2:51 4. There is no sandwich structure 5 m beneath the dam foundation rock mass ground surface, the thickness of which surpassing 5 cm. It has saved a large amount of investment for TGP construction by utilization of the lower part of weakly weathered rock mass as dam foundation. The achievements of utilization of the lower weakly weathered rock mass as dam foundation By utilization of the lower weakly weathered rock mass as dam foundation base, it has obtained great benefits economically and technologically as follows. 1. The percentage of dam foundation ground surface for lower part of weakly weathered rock mass is 39%. 2. It has reduced the rock excavation amount about m It has saved the concrete about m It was easier for the dam construction since the dam foundation ground surface was much flat. 5. A certain construction time was shortened for the project. Conclusions The weathered crust rock mass in China Three Gorges Dam Area has a thickness of m, with four different weathering state rocks such as loose, half loose, half hard and hard and four different weathered zones such as complete, intense, weak and light. It has set a rock mass quality evaluation criterion with TGP characteristic Three Gorges YZP Method. The lower part of weakly weathered rock mass was utilized as dam foundation after consolidation grouting treatment, which meets the grade A quality requirement. References 1. Wang H, Zuo C (1999) Utilization of the dam foundation rockmass about the small and medium hydropower stations in hunan. Hunan Geol Z1:84 88 (in Chinese) 2. Shen G, Yang G (1997) The application of using the weakly weathered rock as a gravity dam foundation plane for transshipment in reservoir engineering. Zhejiang Hydrotech 01:29 32 (in Chinese) 3. Suo S-R, Xu R-P, Yong YE (2006) Weathered rock and selection of foundation surface of concrete dams. Adv Sci Technol Water Resour 05:45 47 (in Chinese) 4. Xiao R-Y, Cai J-M (1988) The issue on utilizing the weathered rock of volcanic in Fu Jian. Water Power 04:28 32 (in Chinese) 5. Ren Z, Ma D, Shen T et al (1998) Research on rock mass of the Three Gorges Project dam foundation. China University of Geosciences Press, Wuhan (in Chinese) 6. Huang Y-Y, Wang Z-G (1995) Understanding and practice of the use for the weakly weathered rock masses. Yangtze River 06:33 36 (in Chinese) 7. Gokay MK (2003) Influence of natural weathering on rock mass. Union Chamb Eng Archit Turk 42(1): Zuo S-S, Ren G-M (2002) Discussion of using quantitative indexes to study rock mass weathering. Mt Res 03: (in Chinese) 9. Nie D, Han A, Ju G (2002) Study on integrated zoning of weathering degree of rockmass. J Eng Geol 01:20 25 (in Chinese) 10. Feng Q-Z, Chen L, Nie D (2001) Research on quantifiable zoning of weathering degree of rockmass. J Geol Hazards Environ Protect 12(2):76 79 (in Chinese) 11. Li Z-M (1999) Elastic wave testing technique on the three gorges dam foundation plane. China Three Gorges Constr 03:13 14 (in Chinese)