Case Study on Environmental Geotechnology Problems in Development and Planning of Small and Medium-sized City

Xinmo Zhou Department of Architecture, University, Shaoxing,

Hanyu Miao College of Public Administration, Nanjing Agriculture University, Nanjing, China

Wei Wang Department of Civil Engineering, Shaoxing University, Shaoxing, China

Minyan Guo* Department of Architecture, Shaoxing University, Shaoxing, China *corresponding author, email: [email protected]

Na Li Department of Civil Engineering, Shaoxing University, Shaoxing, China

Feifei Tao School of Chemistry and Chemical Engineering, Shaoxing University, Shaoxing, China

Huaqiang Tao Shuanghe Environment Construction Co. Ltd, Shaoxing, China

ABSTRACT Environmental geotechnology plays a significant partc in planning and development for small and medium-sized cities. As China’s famous historical and cultural city, Shaoxing city is also facing such geotechnical engineering problems. Through the analysis of geographical position, geological conditions, climate characteristics, and current situation of social development of Shaoxing city, the environmental geotechnical engineering problems was studied in terms of the deformation of soft foundation and ground, sewage sludge, and municipal waste disposal in city planning. According to the characteristics of small and medium-sized cities’ development, feasible technical methods to solve the above discussed problems in environmental geotechnical engineering were explored. KEYWORDS: environmental geotechnology; small and medium-sized city planning; soft foundation; sewage sludge; solid waste

INTRODUCTION During the thirty years after reforming and opening up policy, with rapid economic development and urban construction, continuous increase of resident population, growing influence of human activities on environment, relative environmental problems are increasingly outstanding and the environmental geotechnical engineering problems are arising accordingly. For example, a recent landslide accident occurred in Shenzhen in July 2005, on the construction

- 4397 - Vol. 21[2016], Bund. 13 4398 stage of the foundation pit engineering for Guangzhou Haizhu City Plaza, because of the large displacement of the building envelope, the surrounding buildings and pipelines were broken which caused three deaths and eight injured; in 2009, the collapse of one solid waste landfill site in Shenzhen, hundreds tons of waste and sludge flowed to Buji River, and a large amount of toxic wastewater containing heavy metal streamed via Shenzhen to Hong Kong, leading to a large area of water and soil pollution. If the city managers and builders do not attach importance to the environmental geotechnical engineering problems in city development planning, similar events are likely to happen again in the future. Shaoxing is the one of the first 24 historical and cultural cities in China, the important development open city in the southern wing of Yangtze River Delta, and also the National Sanitary City, National Environmental Protection Model City, National Garden City, National Excellent Tourism City. Since the establishment of Keqiao and approved by State Council in 2013, Shaoxing urban area expanded from the original 362 sq.km to 2942 sq.km, ranking second in Zhejiang Province. As one of the transport hub cities in Yangtze River Delta region, and closer contact with city and city, Shaoxing was integrated into the 90 minutes economic circle of Shanghai metropolitan district, which has an irreplaceable and special geographical location and competitive advantage in the Yangtze River Delta city group. With the expansion of city size and the increase of large-scale urban projects, such as the construction of subway, large-scale transport networks, residential and commercial centers, etc., new problems related to environmental geotechnical engineering appear. In this paper, based on the development process, from the aspects of deformation of soft foundation and ground, sewage sludge and municipal solid waste problems, the environmental geotechnical engineering problems was elaborated, and feasible solutions were proposed, which provided a reference for the similar cities’ planning and development.

ENVIRONMENTAL GEOTECHNOLOGY

Definition Environmental Geotechnology was firstly introduced at the 10th International Society for Soil Mechanics and Foundation Engineering which was held in 1981 in Stockholm. It is a new interdisciplinary covering the environmental science and engineering problems involved in geotechnical mechanics, environmental engineering and geology engineering and other disciplines [1]. Applying the solutions, views and technology of geotechnical mechanics, environmental geotechnology aims to reduce or eliminate the adverse effects of human activities on environment, ensure the sustainable coordinated development between human living and engineering activities and environment. The research is divided into two parts. The first is the big environmental issues of mutual interaction between human beings and natural environment. By studying the generation mechanism, inducing factors, and harm effects of earthquakes, soil degradation, storm surges caused by natural disaster, geotechnology was used to withstand these environmental problems. The other one is little engineering problems of mutual interaction between human living and engineering activities, and environment. These problems are mainly caused by human beings activities on the surrounding environment. With the acceleration of urbanization, intensive human living and production will certainly generate a lot of waste which will inevitably harm our living environment. During the project construction, the squeezing effect caused by pilling, the vibration Vol. 21[2016], Bund. 13 4399 caused by dynamic compaction, and rock-soil body change caused by shield construction will adversely affect the surrounding environment [2].

Engineering geological characteristics Deformation of soft foundation and ground Shaoxing city is located in China’s southeast coast areas, which is the southern wing of the Yangtze River Delta, at latitude 29°14' to 30°16', longitude 119°53' to 121°13', east to Ningbo city and west to Hangzhou city, with a distance of 232 km north to Shanghai. The total area is 8256 sq.km, of which the urban area is 3000 sq.km with a population of 4.34 million. It is an important developed open city among the Yangtze River Delta cities bordered by mountain Kuaijishan to the south, ShaoYu Plain (also known as the Mountain Plain) to the north. With densely covered rivers and lakes, and numerous monuments, there are about 1900 kilometers of rivers and streams, the main rivers are Cao E River, Puyangjiang, Hangyong Canal, and the main lakes are Jinghu New Area. Total water resource is 58.8 billion cubic meters, and 17,000 hectares fresh water is available for farming. The southern part of Shaoxing city is hilly area that is bedrock exposed region, and the north-central plains area is with large soft soil distribution. The topographic map is shown in Figure 1.

Figure 1: Shaoxing city topographic map The soft soil layer mainly distribute in the plain surrounding Shaoxing and Keqiao, and the gullies in the river network, from the gully upstream to downstream, from south to north, with gradual increasing thickness, and the maximum thickness is greater than 80m [3-4]. According to the genesis and physical mechanic properties of rock layer, as well as the habits in engineering geological survey industry in Shaoxing area, combined with the preliminary research results of Sequence Stratigraphic Study on the Area since 15000a B. P. conducted by Lin Chunming [5], it is divided into 10 engineering geological layers from top to bottom [4], and further divided into sub-layers in the same layer according to its lithology and physical and mechanical properties differences. On the basis of the statistical analysis of the collected engineering geological survey data [6], the main physical and mechanical index on soil or rock Vol. 21[2016], Bund. 13 4400 layers of foundation in the center area of Shaoxing city are shown in Table 1. In this table, fk means characteristic value of soil bearing capacity.

Table 1: Main physical and mechanical index on soil or rock layers of foundation

Countermeasures and processing methods During rainy season or with rainstorms, the ground deformation caused by subway and other underground space development has great harm which easily leads to project collapse or landslides. For the soft foundation deformation problem, in the case of project planning, design and preparation of construction program, the adverse effects on environment should be fully demonstrated. If there are some issues which may cause serious damage to the surrounding environment, it is necessary to modify the design or select an alternative site. For soft foundations, necessary reinforcement to prevent liquefaction sand foundation shall be taken, such as vacuum preloading, surcharge preloading technology, so as to improve the foundation bearing capacity. For the underground space and tunnel project, we can learn more mature experience from Shanghai, Guangzhou and other coastal cities, and apply the shield methods and pipe-jacking technology to overcome the shortcomings. Due to the complexity of soft soil characteristics in Shaoxing area, the experimental data and constitutive model which took Shaoxing seashore soft soil as the subject should be considered and used in the specific design and computing process. For example, for seashore soft soil foundation, a more accurate stress-strain model was proposed as shown in reference [7]: αe −Gqe / u ()1- Gqu qq=−+α u (1 e ) (1) qGu + e Vol. 21[2016], Bund. 13 4401

Wherein, q represents the deviatoric stress, ε represents the axial strain, qu represents the triaxial shear strength, G represents the initial shear modulus, α is a model parameter between 0 and 1. Meanwhile, a more appropriate soft soil treatment method shall be applied to meet the needs of urban planning. For example, the method of using LCSG pile to treat the seashore super soft soil used in reference [8] may be more appropriate. The cross section and profile section of the pile is shown in Figure 2.

gravel

gravel pile concrete

the LCSG pile CSC pile

(a) Cross section (b) Profile section Figure 2: Improved section of LCSG pile

Effect on Shaoxing city planning Based on basic characteristics of engineering geology and urban development process, although Shaoxing is a small and medium-sized city, the floor space is increasingly crowded, and the building land is gradually tensing. Urban underground space as a new type of land and resources, with timely and orderly manner to develop and utilize, it can make the limited urban land play a greater role, which is a new trend in urban planning. For examples, Tokyo, New York, Paris and other world-class cities, with decades or even century’s time, the underground space network of subway and tunnel were built. Currently, the small and medium-sized city such as Shaoxing also has the ability to develop and utilize the underground space. One planning and development idea for Shaoxing city is to develop the underground space. The use of underground space not only increases the degree of urbanization, but also helps protect the ecological balance and reduce the vandalism to natural environment. Moreover, with the advantage of low noise, low power consumption, shockproof and other properties; the underground space enhances the overall urban disaster prevention and survivability. Recently, State Council has formally approved the first period plan of Shaoxing urban rail transit construction (2016-2021), including the main line and extension line project of Line 1, and the first-stage project of Line 2, with a total investment of 29.2 billion Yuan. The main line project of Line 1 is from Jianhu town in to Diyang Road station in Keqiao District, the length is 23.6 km with 17 stations. The extension line is from Qiandadao station to Keqiao Station, about 6.7 km length and 6 stations. The investment for the main line and extension line of Line 1 is 21.411 billion Yuan, and the planning construction period is from 2016 to 2020. The first-stage project of Line 2 is from Yuexi Road station to Yuexing Road station with 10.8 km length and 8 stations, the total investment of 7.752 Vol. 21[2016], Bund. 13 4402 billion Yuan, and the planning construction period is from 2017 to 2021. The Shaoxing subway planning map is shown in Figure 3.

Figure 3: Shaoxing subway planning map

Water resources situation and countermeasures

Water resources pollution and soil erosion During the long urban development process along with nature transformation, there is no much attention on environment protection. Especially with the growing population, expanding scale of industrial and agricultural production, and direct discharge of living and industrial waste, a large number of fresh water resources are contaminated which leads to the limited water resources can not meet people’s growing needs. In recent years, Shaoxing City has invested a lot of money for treating the living and production sewage, which effectively eases water pollution to some extent.. Solutions and processing methods The basic requirements for site selection of sewage treatment plant include: (1) should be located in low-lying place, which is easy for urban sewage flowing into the plant; (2) should be Vol. 21[2016], Bund. 13 4403 located in the vicinity of water bodies to facilitate the treated sewage flowing into the nearest water bodies; (3) should be located in the downstream of towns, factories and residential areas and below the dominant wind direction in summer; (4) should not be located low-lying areas prone to flood in rainy seasons to prevent pollution of water bodies; (5) combined with short and long term urban development issues, urban planning should be taken into account together. According to the above requirements, combined with the overall planning of Shaoxing City, the sewage plant site is located in the northeast area near to Hangzhou Bay, east to Cao’erjiang, north to the , with a total area of 1,800 acres. Shaoxing sewage treatment plant is the current largest printing and dyeing wastewater treatment plant designed to handle capacity of 100 tons/day in long-term planning, covering more than 2,000 acres. According to the principles in the overall planning “unified planning, phased implementation”, the sewage treatment plant was built by both Shaoxing city and county, with a total designed capacity of 500,000 t/d for the first period project, in which, the designed capacity of 300,000 t/d sewage treatment plant was put into operation in June 2001. The designed capacity for Phase II project of Shaoxing sewage treatment plant is 300,000 m3/d with 640 million Yuan investment, the processing capacity can reach 400,000 m3/d after preprocessing transformation, and the annual handling capacity reaches 140 million tons, which reduces pollution emissions of biochemical oxygen demand (BOD) of 8400 tons, chemical oxygen demand (COD) of 21000 tons, ammonia nitrogen (NH3-N) of 326 tons, and total phosphorus (TP) of 65 tons to Qiantang River. Firstly, these measures upgrade the grade of Shaoxing city, improve the quality of life and economy; secondly, it reduces the pollution of Cao E River and Qiantang River; lastly, it promotes the stable development of traditional industry in Shaoxing especially the rice wine and aquaculture industry, forms a reasonable distribution of printing and dyeing, chemical industry and other industries, so as to boost the construction of urban infrastructure. The operation of sewage treatment plants control the industry wastewater and living sewage in Shaoxing city and county, with significant improvement on water quality, which has brought great benefits for Shaoxing’s economic construction, urban construction and environmental construction. Consideration in urban planning The planning positioning for Shaoxing city is a national ecological civilization city. The planning guidelines are to strengthen the scientific protection on ecological environmental resources, delineate the ecological red line, and control the ecological background to maintain the unique attractive ecological pattern of mountain, water and city. The river water quality meets the functional area requirements; the days with good air quality increase year by year, reduce the average carbon intensity to the maximum possible extent, promote low-carbon ecological zone construction, and build a suitable indicator system of ecological low-carbon development. Therefore, in city planning layout, the northern part is with industry-oriented economy and emerging industries features; the central part is with service-oriented economy and urban economy features; the southern part is with ecological-oriented economy and leisure and health features. Urban sports and leisure base in Jianhu-Keyan region, elderly care and health services base in Kuaijishan region, characteristic culture and leisure base in Lanting region, national culture water scenic area in Cao E River region, and rural leisure base in Siming Mountain region are constructed. The planning layout for Shaoxing city is shown in Figure 4. Vol. 21[2016], Bund. 13 4404

Hangzhou Bay

Figure 4: Overall planning layout of Shaoxing city (Cited from: http://news.focus.cn/sx/2014-04-09/4913263.html)

Municipal waste disposals Waste situation In 2015, the resident population in Shaoxing City is 496.8 million, accounting for 8.96% in Zhejiang province. A large number of people produce a large amount of solid waste and garbage, and the main ingredients are shown in Figure 5. According to preliminary statistics and projections, the garbage will rapidly increase, and the daily amount of waste per capita and total amount is shown in Table 2. The daily amount of garbage of only the three zones of Yuecheng District, Keqiao District and Shangyu District in 2014 has reached 2600t, and with 7% to 8% annual growth rate in recent years. According to this growth rate, the waste landfill site in main city will basically become saturated in 2017. These wastes have lead to potential threat to city image, disease breeding and spreading, environmental destruction and other problems.

Table 2 : The prediction structure of garbage amount in Shaoxing City Daily amount per Year Population/10,000 Total amount (t/d) capita(kg/(d.p)) 2009 48.4 0.87 422 2015 61.7 1.2 701 2020 82.9 1.4 1161

Vol. 21[2016], Bund. 13 4405

Figure 5: Waste composition

Countermeasures and processing methods The main treatment methods for existing municipal waste are incineration method, land filing method and recycling method. Incineration causes air pollution, landfill easily leads to environmental disasters such as landfill slope failure, leachate leaking, and disorder gas spreading to atmosphere. Two major issues which land filling method faces are: on one hand, the sedimentation of solid landfill body and uneven settlement affects the safe operation of the landfill treatment system; on the other hand, how to properly design the slope, it is difficult to find a balance in both economic and security aspect. To solve the above problem, it is necessary to find a sustainable landfill technology or other more rational solid waste disposal methods. By means of using leachate recirculation to accelerate waste decomposition, optimizing the landfill partition, reducing landfill leachate levels and other measures to improve the landfill technology; municipal solid waste incineration plant was constructed. Shaoxing City has proposed to build the waste incineration power plant projects (PPP) in cycling ecological industrial park, the project is located in northern waterfront land in Keqiao Binhai Industrial Zone, Shaoxing City, Zhejiang province, south to the planning Binhai road, about 5 km distance east to the Cao E River, north to Hangzhou Bay, west to Xiaoshan border. The construction scale is 2250 t/d for the municipal waste incineration power plan with 3 MSW incineration line. The total investment is 1.2 billion Yuan. It will gradually replace the landfill site, but need to reprocess the generated flue gas, and make secondary use of some solid waste, such as abandoned buildings concrete can be used for the production of tiles, wallboard and other building materials, the waste residue soil can be applied to road construction, pile filling, foundation reinforcements, etc. For the existing landfills site, long time settlement observation shall be taken, and a mathematical model shall be established based on observation data in order to evaluate its safety and impact on the surrounding environment and provide technical reference for urban planning. Equation (2) is a typical landfill construction post settlement model, wherein, s represents the post settlement, t represents time, a, b and k are three undetermined parameters [9]. abe−−kb() at− ab s = (2) ae−−kb() at− b Planning and selection for waste incineration power plant site Generally, the site selection for waste incineration power plant project should follow the following principles [9,10]: (1) built in downstream of the river system, but not in the upstream; (2) built in region that the soil water system was severely contaminated, but not in the area with good natural environment; (3) built in the place a little far away from the city, but not on city outskirts; (4) built in the area with convenient traffic with a number of roads access, but not in the place with only one road access. According to the above requirements, combined with the overall planning layout of Shaoxing city, the waste Vol. 21[2016], Bund. 13 4406 incineration power plant site is located in Binhai Industrial Zone, Keqiao district, Shaoxing city, the effect drawing is shown in Figure 6.

Figure 6: A photograph of Shaoxing municipal waste incineration power plant

CONCLUSIONS During the accelerating process of urbanization, environmental geotechnical problems have aroused great attention on relevant government departments; a lot of manpower, material and financial resources have been invested to solve these difficulties. It is not only an opportunity but also a challenge for the geotechnical works who must strive to combine the geotechnical engineering and environmental engineering, geological engineering and other related disciplines together, look for new technologies, develop new areas, in order to solve the environmental geotechnical problems in the development process of small and medium cities before they occur.

ACKNOWLEDGMENTS The authors thank the reviewers who gave a through and careful reading to the original manuscript. Their comments are greatly appreciated and have help to improve the quality of this paper. This research is partly supported by the National Natural Science Foundation of China (41202222), and the Ministry of Housing and Urban-Rural Development of China (2012-k3-4, 2015-k4-003, 2016-k5-008). REFERENCES 1. Hsai-Yang Fang and Hilary I Inyang: “Environmental Geotechnology”, Proceedings of the 3rd International Symposium-volume one, Technomic Publishing Company, Inc, 1996.

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Editor’s note. This paper may be referred to, in other articles, as: Xinmo Zhou, Hanyu Miao, Wei Wang, Minyan Guo, Na Li, Feifei Tao, Huaqiang Tao: “Case Study on Environmental Geotechnology Problems in Development and Planning of Small and Medium-sized City” Electronic Journal of Geotechnical Engineering, 2016 (21.13), pp 4397-4407. Available at ejge.com.