Classification and quantification of excavated soil and construction sludge: A case study in Wenzhou, China

Abstract

With rapid urbanization in China, a large amount of excavated soil and construction sludge is being generated from geotechnical and underground engineering. For sustainable management of these construction wastes, it is essential to quantify their production first. The present study has attempted to classify the excavated soil and construction sludge according to their composition and geotechnical properties (particle size, water content, plasticity index). Based on these classifications, a new approach was proposed to quantify the production. The said approach was based on multi-source information, such as the urban topographic map, geological survey reports, urban master plan, and remote sensing images. A case study in Wenzhou city of China was also pursued to illustrate the validity of the newly developed approach. The research showed that in 2021–2025, the total excavated soils and construction sludge production in Wenzhou would reach 107.5 × 10⁶ and 81.7 × 10⁶ m³, respectively. Furthermore, the excavated soil was classified into the miscellaneous fill, crust clay, muddy clay and mud with silty sand. Likewise, the construction sludge was classified as liquid sludge and paste-like sludge. The classification and quantification can serve as guidance for disposal and recycling, thereby leading to high-level management of waste disposal.

Graphical abstract

Keywords

excavated soil / construction sludge / geotechnical and underground engineering / production / classification

1 Introduction

With rapid urbanization in China, the construction activities there have undergone wide expansion and active promotion. At the same time, this also led to the generation of a huge amount of construction and demolition waste (C&D waste) [1]. Excavated soil and construction sludge both belong to C&D waste [2,3]. Excavated soil mainly refers to the soil generated during the excavation process in building foundation and tunneling engineering [4]. Construction sludge is the sludge generated from construction work, such as cast-in-place concrete piles, continuous diaphragm walls, and shield tunnel [5]. Tab.1 shows the C&D waste generated in 12 typical cities of China, including 4 first-tier cities (i.e., Beijing, Shanghai, Guangzhou, and Shenzhen), 4 new first-tier cities (i.e., Hangzhou, Chengdu, Xi’an and Changsha) and 4 other cities (i.e., Jinan, Hohhot, Handan, and Tai’an). The total amount of C&D waste reached more than 740 × 10⁶ tons of which excavated soil alone was 598 × 10⁶ tons, accounting for more than 80% of the total waste. Furthermore, as the main part of the construction waste, construction sludge accounts for more than 50% of the total construction waste in Shanghai and Shenzhen. In Hangzhou, the construction sludge even reaches nearly 95% of the total construction waste. Needless to say, with further development of urban underground space, the amount of excavated soil and construction sludge would keep increasing, and therefore, proper management of such waste with respect to disposal and recycling is of utmost importance.

Quantification of production is the premise of managing excavated soil and construction sludge. Previous studies about the quantification method mainly focused on demolition waste and construction waste (excluding construction sludge), while only a handful of studies dealt with the excavated soil and construction sludge [6–8]. Qiao et al. [7] analyzed the current output of construction waste (excluding construction sludge) in Shandong Province by estimating building area. They predicted the output of the next few years using the exponential smoothing method. Their results indicated that the amount of construction waste (excluding construction sludge) would reach 141 × 10⁶ tons by 2025. Similar studies using the building area to quantify production had also been reported [9–12]. Material flow analysis (MFA) is another commonly used approach to calculate the production of minerals, construction waste (excluding construction sludge), and demolition waste [13–15]. Gao et al. [16] proposed a dynamic material flow and stock model which integrated the historical rural-urban land transition to estimate the quantity of demolition waste from the residential buildings of Shanghai. Results showed that demolition waste is expected to peak at 29 ×10⁶ tons in the 2060s. In recent years, geographic information system (GIS) has become an important aid for gathering and analyzing geospatial information data in space [11]. Wu et al. [17] proposed and applied a GIS-based model to estimate the production of demolition waste in Shenzhen, China. Results showed that over 135 × 10⁶ tons of demolition waste would be generated in the Nanshan district during 2015–2060. Obviously, all the existing production quantification methods had been employed for construction and demolition wastes, but not specifically for the excavated soil and construction sludge.

Current studies on excavated soil and construction sludge primarily focused on the classification, recycling and management. Due to the difficulty of quantification, such studies rarely involved the production of excavated soils and construction sludge. Since the 1990s, some scholars began to consider re-utilization of excavated soil and construction sludge from the environmental, geotechnical point of view [5,18–21]. The Japanese Ministry of Land, Infrastructure and Transport [22] integrated the related researches of Kamon and proposed a classification of excavated soils and construction sludge to promote their reuse. In the last 20 years, modification and improvement treatment of excavated soil and construction sludge such as dehydration, solidification, and stabilization have become the primary focus of several researchers [23–27]. Accordingly, studies related to recycling and management also increased [28–31]. In addition, natural contamination inside these soil materials also became an attractive topic of research [4,32].

In the present work, the excavated soils and construction sludge were classified according to composition and geotechnical properties (particle size, water content, plasticity index), and based on the classification, an approach to quantify the production of excavated soils and construction sludge was proposed. By collecting information from multi-sources, such as urban topographic maps, geological survey reports, and construction master plan, combined with remote sensing (RS) images, the proposed approach can be applied to areas with different terrains generating more reliable results. In addition, a real case was used to calculate the excavated soils and construction sludge production in Wenzhou, a typical multi-terrain city in southeast China for better evaluation. The classification and quantification of excavated soils and construction sludge can serve as a reference for disposal and recycling, thereby providing a basis for planning disposal facilities and leading to high-level management of waste disposal.

2 Methodology

Data from multiple sources were used, and a newly developed method was employed, divided into five steps as described below. Fig.1 shows the flowchart of the method used in the study.

Step 1: Different terrains often have different geological structures, which lead to differences in the composition of the excavated soils and construction sludge. Therefore, a studied city should be divided according to its terrain. For this, an urban topographic map should be collected first and then divided into several areas. The different terrains such as plains, mountains, basins, and islands should be treated separately.

Step 2: Based on the terrain-wise division (Step 1), geological survey reports of each kind of area should be collected to determine the soil strata. The thickness of each soil stratum within the excavation depth should be recorded to calculate the proportion of each stratum in the whole strata. For example, say, a construction site has four soil strata, which are miscellaneous fill (0.5 m), silt (1 m), muddy clay (3 m), and medium sand (1 m). Assuming the excavation depth is 5 m, the excavated soils could be classified into four types (miscellaneous fill, silt, muddy clay, and medium sand), accounting for 10%, 20%, 60%, and 10%, respectively.

Similarly, the construction sludge can be classified into liquid sludge (high water content and uniform) and paste-like sludge (low water content with coarse dregs). The construction sludge is usually liquid in areas where the soil strata are either thick clay soil or thick muddy soil. On the other hand, in areas with thick sand strata and shallow bedrock, the construction sludge is paste-like (low water content with some coarse dregs) because the pile foundation reaches the bedrock easily. Therefore, the type of construction sludge is directly related to the local terrain.

Step 3: Since excavated soil and construction sludge are underground wastes, the amount produced is directly related to the construction land area (S). Therefore, to quantify these wastes, the area S needs to be estimated. As the first step to this, the urban master plan should be used to determine the location and planned area of construction. Additionally, technologies such as RS, GIS, and unmanned aerial vehicle (UAV) are also useful in the area measurement. Through these technologies, the scope of a construction land can be accurately identified, and the coverage area can be calculated. Considering that the master plan is only effective for a short period, estimating the production for the next 5–10 years would be more accurate. To note, previous studies on the quantification of demolition waste were often based on the calculation of the construction gross area (CGA) [10–12].

Step 4: Based on the divisions in Step 1, representative construction sites in each area should be selected for investigation. These sites must contain various construction activities like building construction, metro engineering, or municipal pipe network constructions for accurate estimation. Furthermore, site geological survey reports, project design documents should be referenced to determine the production (q) of excavated soils and construction sludge per unit land area for construction. The local excavated soil and construction sludge should be characterized during the investigation to determine soil and sludge composition.

Step 5: Based on the waste classification (in Step 2), the estimated land area for construction (in Step 3), and the production of excavated soils per land area (in Step 4), the amount of a certain kind of excavated soil (Q_{ij}^{\text{e}}) in a construction site can be calculated as:

(1)Q_{ij}^{\text{e}}={\gamma }_{ij}{q}_i^{\text{e}}{S}_i,

where i means the ith site out of n sites (i = 1,2,...,n), j means the jth soil stratum from top at the ith construction site (j = 1,2,...,m), Q_{ij}^{\text{e}} is the amount of the excavated soil produced in the jth stratum, γ_ij refers to the proportion of jth soil stratum with respect to the whole strata, q_i^{\text{e}} is the amount of excavated soils generated per unit area of the construction land, S_i means the area of the construction land. For example, assuming there are three construction sites, and the first soil stratum in each site is miscellaneous fill, then the total amount of the miscellaneous fill is the sum of the first soil stratum of all the three sites.

For each kind of excavated soil, the total amount of excavated soils (Q_{\text{t}}^{\text{e}}) could be calculated as follows:

(2)Q_{\text{t}}^{\text{e}}=\sum _{i=1}^n\sum _{j=1}^m{\gamma }_{ij}{q}_i^{\text{e}}{S}_i,

(3)\sum _{j=1}^m{\gamma }_{ij}=1,

where n is the number of the construction site (i = 1,2,...,n), m is the number of soil strata in the ith construction site (j = 1,2,...,m).

As for construction sludge, the production of construction sludge (Q_i^{\text{c}}) in the ith construction site is calculated from Eq. (4):

(4)Q_i^{\text{c}}=q_i^{\text{c}}{S}_i,

where i refers to the ith site out of n sites (i = 1,2,...,n), q_i^{\text{c}} is the amount of construction sludge of per unit area of the construction land at the ith site, S_i is the area of the construction land involved. For a construction site, the type of construction sludge is usually uniform. For example, the construction sludge in the riverside area is often liquid, and the construction sludge in the hill area is often paste-like.

With respect to each kind of construction sludge, the total amount of construction sludge (Q_{\text{t}}^{\text{c}}) could be calculated as follows:

(5)Q_{\text{t}}^{\text{c}}=\sum _{i=1}^n{q}_i^{\text{c}}{S}_i,

where n is the number of the construction site (i = 1,2,...,n).

Wenzhou, a coastal city in southeast China, was chosen to demonstrate our approach. Wenzhou is the southernmost city of Zhejiang Province, with a total area of 11612.94 km² and a population of 9.3 × 10⁶. It has jurisdiction over four districts (Lucheng district, Ouhai district, Longwan district, and Dongtou district), three county-level cities (Rui’an city, Yueqing city, and Longgang city), and five counties (Yongjia county, Pingyang county, Cangnan county, Wencheng county, and Taishun county). The present study was based on the four urban districts of Wenzhou, namely Lucheng, Ouhai, Longwan, and Dongtou. As a city with complex terrain, including hills, plains, rivers, and ocean, the case study of Wenzhou can be considered as a general reference.

3 A case study in Wenzhou, China

3.1 Division refers to terrain

From the urban topographic map, Wenzhou’s terrain has the characteristics of “70% hills, 20% rivers, and 10% farmlands”. There are hills in the central and western parts, while coastal plains and tidal flats in the east. As a result, the whole terrain is high in the west and low in the east. Oujiang River, the largest river in Wenzhou, flows through the north of the four urban districts into the East China Sea.

The urban area of Wenzhou can be divided into six types of landforms, as shown in Fig.2. They are the hill, plain, riverside, estuarine, reclamation, and island areas. The Lucheng district mainly includes the riverside and hill areas with some estuarine areas in the lower reaches of the Oujiang River. On the other hand, the Ouhai district comprises an urban area with hills and plains distributed alternately. The third district, Longwan is divided into three types: the reclamation, estuarine and plain areas. Lastly, the Dongtou district is a natural island except for the Lingkun islet, which belongs to the estuarine-reclamation area.

3.2 Classifying the excavated soils and construction sludge in each division

A total of 25 geological survey reports were collected from the Wenzhou Housing and Urban-Rural Development Bureau, and the geological profiles of each area are shown in Fig.3. The survey reports showed that building construction in Wenzhou generally included two types of basement: 1 level and 2 levels. The excavation depth of 1-level basement was about 6.5 m, and that of the 2-level was about 10 m. The corresponding depth position in Fig.3 is marked with a red dashed line. In addition, metro construction excavated up to a depth of 20–30 m; so, the geological profiles within 30 m received more attention. The distribution characteristics of the soil strata in each division are as follows.

(a) Hill area: The soil strata from top to bottom are of miscellaneous fill, clay, mud, silty clay with gravel, strongly weathered bedrock and moderately weathered bedrock. Compared with the other areas, the soft soil strata are thinner and about 10 m depth under which there are shallow bedrocks with different degrees of weathering.

(b) Plain area: The soil strata from top to bottom contains miscellaneous fill, clay, mud, muddy clay, and clay. The geology of this area is dominated by thick, soft soil strata.

(c) Riverside area: The soil strata from top to bottom are of miscellaneous fill, clay, mud with silty sand, silty sand with mud, mud, mud with silty sand, and muddy clay. Unlike the plain area with thick soft-soil strata, the soft-soil strata of riverside contain more sands due to the sedimentation from the Oujiang River.

(d) Estuarine area: The soil strata from top to bottom contains miscellaneous fill, clay, mud, muddy clay, and clay. The estuarine area has the characteristics of both the plain and riverside areas. In the shallow strata (within 40 m), there is a thick soft-soil stratum (similar to the plain area) formed by an accumulation of mud. In the deep strata (below 40 m), there is a soft-soil stratum interlaid with more sands and the estuarine delta features. In addition, due to the backflow of the East China Sea, the soil in the estuarine area often contains salt, debris, and shells.

(e) Reclamation area: The soil strata from top to bottom comprises miscellaneous fill, clay, muddy silty clay, mud with silty sand, mud, and muddy clay. Since the reclamation area is man-made, the upper soil stratum of mixed fill is thick (miscellaneous fill, clay, muddy silty clay, mud with silty sand).

(f) Island area: The soil strata from top to bottom are miscellaneous fill, mud, gravelly sand, strongly weathered bedrock, and moderately weathered bedrock. There is a lack of crust clay beneath the surface miscellaneous fill. The soft soil stratum is below the miscellaneous fill, and the gravel sand and bedrock with different degrees of weathering are under the mud stratum of thickness ~10 m. The bedrock stratum is inclined.

From the geological survey reports in Fig.3 and the description of soil strata distribution above, the proportions of different soil strata in different divisions are shown in Tab.2. Since the proportion of soil strata depends upon the basement type, the proportions are listed separately according to 1-level and 2-level basements. The main section of the metro construction is located in the Lucheng and Ouhai districts, which are mainly composed of plain areas. Therefore, the soil stratum along the metro route was analyzed as a plain area, and the default excavation depth is 30m. As shown in Tab.2, except for miscellaneous fill and gravel sand, the excavated soil was a different soft soil. To note, the composition of the sludge produced from the construction of the bored pile depended on the depth of the bedrock. In areas with shallow depth of the bedrock, such as the hill or island areas, the pile foundation reaches the bedrock, leading to the formation of paste-like sludge with low water content and more coarse-grained dregs. By contrast, the sludge is liquid with high water content in areas with thick soft-soil strata (e.g., riverside area, estuarine area, plain area, reclamation area, Metro route). The proportion of different soil strata and the sludge characteristics in Tab.2 are the bases for the classification of excavated soils and construction sludge.

3.3 Estimating the land area for construction in the city

The present study involved three types of construction lands as described below.

Type 1: The zones where demolition waste was accumulated but construction work would be carried out according to the master plan in 2021–2025;

Type 2: The zones where buildings are to be demolished and rebuilt according to the master plan in 2021–2025;

Type 3: The zones where land is vacant but construction work would be carried out following the master plan in 2021–2025.

The urban master plan was used to calculate the land area for the construction of the city [33]. According to the plan, each district has its own construction blocks in 2021–2025. In Lucheng district, the building land contains Shuangyu block, Huanwuma block, Wuma business block, Binjiang business block, and Central park block. In Longwan district, the building land comprises Zhuangpupian block, Zhenan science and technology block, Eastern hub block, Oufei block, Jinliwen Expressway East extension line, and Tonghai Avenue, and Luodongnan street. In Ouhai district, the building land contains Guoxi/Zhaixi village, a high-speed railway block, a west railway station block, Tangshuihe Riverbank, and Sanyang wetland. In Dongtou district, the building land only contains Lingkun islet.

For accurate quantification, RS and UAV were applied to distinguish the three types of building land. Additionally, from RSimages of the last 10 years, the construction land area can be estimated. In detail, if the buildings of a site have turned into ruins with time, the site belonged to building land of type 1; a site where the landscape did not change with time belonged to building land of type 2; if a site was either vacant or a grassland, it was of the building land type 3. Accordingly, the area of the construction land was calculated using RS image analysis software. However, when the RS image was not distinct, UAV was used as an auxiliary tool for on-site image acquisition.

With the help of the above two tools, the land area for construction was estimated, as shown in Fig.4. In Lucheng district, the areas of land for construction in Shuangyu block, Huanwuma block, Wuma business block, Binjiang business block, Central park block were 2.36, 0.31, 0.73, 1.67, and 0.72 km², respectively. In Longwan district, the areas in Zhuangpupian block, Zhenan science and technology block, Eastern hub block, Oufei block, Jinliwen Expressway East extension line and Tonghai Avenue, Luodongnan street were 1.27, 6.09, 0.98, 0.81, 0.79, and 0.22 km², respectively. In Ouhai district, the areas in Guoxi/Zhaixi village, High-speed railway block, West railway station block, Tangshuihe Riverbank, Sanyang wetland were 0.08, 2.85, 0.96, 1.77, and 2.01 km², respectively. In Dongtou district, the area in Lingkun islet was 0.73 km². Therefore, the total land area for construction in the city was 24.35 km².

The basement type of the above several blocks are summarized in Tab.3. Low-rise buildings and mid-rise buildings usually have 1-level basement, whereas high-rise buildings in commercial areas usually have 2-level basement. In addition, the total length of metro route in Wenzhou was 32.5 km, with 23 metro stations.

3.4 Generation of excavated soils and construction sludge per unit area of construction land from each landform type

Several corresponding construction sites were selected for investigation from the six landform types described in Section 3.1. These selected sites were Yangfushan Residential Quarter (Riverside area), Oupuyang Public Rental Quarter (Hill area), Longshuipian village in Zhenan science and technology City (Estuarine area), Oujiangkou New District in Lingkun islet (Reclamation area), Sanyang Wetland construction project (Plain area), and Niyuxiang village (Island area). For the study, local geological survey reports were collected, the excavated soils and construction sludge production was investigated, and soil/sludge was sampled. By combining the total amount of excavated soil and construction sludge generated and the construction land area, the amount of excavated soil and construction sludge production per unit area of the construction land was obtained (see Tab.3).

Tab.4 shows that the generation of excavated soil per unit land area was not related to the terrain of the construction site but only related to the number of levels of the basement. A certain correlation exists between the formation of construction sludge and terrain. This is because the higher the water content of the local soil strata, the greater the construction sludge produciton (Estuarine area > Riverside area, Plain area, Reclamation area > Hill area, Island area). As for metro construction, 30000 m³ of excavated soils is produced per kilometer, 100000 m³ of excavated soils is produced in the construction of each metro station, and 100000 m³ of sludge is also produced due to shield tunneling.

4 Results and discussion

4.1 Production of excavated soils and construction sludge

Using the classification of excavated soils and construction sludge (in Section 3.2), the land area for construction (in Section 3.3), and amount of excavated soils and construction sludge generated per unit area (in Section 3.4), the excavated soils and construction sludge production in the years 2021–2025 were calculated using Eqs. (2) and (5) are shown in Tab.5. The total excavated soils and construction sludge production in Lucheng district (Tangshuihe Riverbank, Shuangyu block, Binjiang business block, Central park block, Huanwuma block) was 33.0 × 10⁶ and 21.3 × 10⁶ m³, respectively. The total excavated soils and construction sludge production in Ouhai district (High-speed railway block, Sanyang wetland, West railway station block, Guoxi/Zhaixi village) was 26.1 × 10⁶ and 13.7 × 10⁶ m³, respectively. The total excavated soils and construction sludge production in Longwan district (Zhenan science and technology city, Zhuangpupian block, Eastern hub block, Oufei block, Luodongnan street) was 44.0 × 10⁶ and 43.2 × 10⁶ m³, respectively. The total excavated soils and construction sludge production in Dongtou district (no construction except Lingkun islet) was 1.1 × 10⁶ and 1.2 × 10⁶ m³, respectively. In addition, the metro construction would produce 3.3 × 10⁶ m³ excavated soils and 2.3 × 10⁶ m³ construction sludge. To sum up, in the next five years (2021–2025), the total excavated soils and construction sludge production is anticipated to reach 107.5 × 10⁶ and 81.7 × 10⁶ m³, respectively. The Lucheng district, Ouhai district, Longwan district, and Lingkun islet areas are 294, 614, 279, and 25 km², respectively. The Longwan District, being the smallest urban district, would observe the maximum production of excavated soils and construction sludge, whereas, Ouhai, the largest urban district, would observe the minimum. An obvious imbalance between the production of excavated soils and construction sludge and the area occupied can be speculated in the next five years (2021–2025).

4.2 Classification of excavated soils and construction sludge

Fig.5 shows the production of different types of excavated soils and construction sludge in the next five years (2021–2025). According to the composition and geotechnical properties of soil (particle size, plasticity index and water content), the excavated soils can be divided into four types: miscellaneous fill, crust clay, muddy clay and mud with silty sand, while the construction sludge is divided into two types: liquid sludge and paste-like sludge. The productions of miscellaneous fill, crust clay, muddy clay and clay with sand are 20.2 × 10⁶, 15.2 × 10⁶, 31.1 × 10⁶, and 41.0 × 10⁶ m³, accounting for 19%, 14%, 29%, and 38%, respectively. The productions of liquid sludge and paste-like sludge are 71.5 × 10⁶ and 10.2 × 10⁶ m³, accounting for 88% and 12%, respectively. Clearly, in the next five years (2021–2025), muddy clay, mud with silty sand, and liquid sludge would become the focus of disposal.

Tab.6 shows the geotechnical properties of our collected samples. The miscellaneous fill and crust clay, which are excavated soils of good quality, can be utilized for road sub-base, as filling or backfill for foundations of embankments, and for protection of slopes. The muddy clay and mud with silty sand, which are excavated soils of poor quality, are suitable for land reclamation. As for the two types of construction sludge, the materials are summarized as 1) flowable materials for grouting or excavating sludge, 2) earthen materials for embankment or backfilling, 3) clay materials for cement or ceramic manufacturing, and 4) granular materials for use as aggregates [21].

4.3 Discussion

By using the proposed approach, based on the construction area of Wenzhou from 2018 to 2020 [34], the production of excavated soil was predicted as 16.9 × 10⁶ m³ in 2018, 18.7 × 10⁶ m³ in 2019, and 20.5 × 10⁶ m³ in 2020. Through interviews with the Wenzhou Housing and Urban-Rural Development Bureau, Wenzhou Ecological and Environment Bureau, it was learnt that the actual amount of excavated soil generated in Wenzhou was 16 × 10⁶ m³ in 2018, 18 × 10⁶ m³ in 2019, and 19.5 × 10⁶ m³ in 2020. The relative errors of predictions are 5.6%, 3.9%, and 5.2%, respectively. Since the quantity of excavated soils estimated in the current study represents the total amount for the next five years (2021–2025), the average annual quantity would be about 21.5 × 10⁶ m³, which is consistent with the dynamic increase of the annual excavated soil production. For construction sludge, the predicted productions in 2019 and 2020 are 12.4 × 10⁶ and 15.1 × 10⁶ m³, respectively, while the actual production was 12 × 10⁶ m³ in 2019 and 15 × 10⁶ m³ in 2020 (The relative errors are 3.3% and 0.7%, respectively). The estimated annual production of the sludge, 16.3 × 10⁶ m³ is also consistent with the dynamic change of sludge production. In the past two years, Wenzhou demolited and reconstructed 96 villages, covering an area of 17.3 km² [35]. Besides, Metro Line 1 and Oufei reclamation areas would be constructed in the next five years [36]. Therefore, the calculated production of excavated soils and construction sludge is in accord with the actual situation of urban construction.

The approach developed in the present study should be carried out according to the local characteristics of the construction land. Reasonable division of landform in Step 1 should be done considering the actual topography of the site of interest. For example, in China, where the terrain is “High in the West and low in the East”, plain is the main terrain in the Middle or Northeast, the plateau is the main part in the Northwest, and mountains are primarily in the Southwest. Different representative soils from different regions were considered while classifying the excavated soil and construction sludge (Step 2). For example, located in Nanjing beside the Yangtze River, the sand content of excavated soil is high. Located in Xi’an on the Loess Plateau, the excavated soil is mainly loess with low water content. To estimate the area of the construction land (Step 3), one should refer to the government master plan, combined with RS, GIS, and UAV to verify the estimation accuracy. To calculate the quantity of excavated soils and construction sludge generated per unit area of the construction land in each division (Step 4), it is necessary to select representative construction sites for investigation and check the obtained data using construction drawings to ensure the reliability of the sources.

The approach for quantifying excavated soils and construction sludge has the following advantages: 1) quantification with classification helps to manage disposal and recycling; 2) being reliable because of collecting information from official and investigated representative construction sites; 3) shows dynamic changes due to the use of various instrumental analyses, such as RS, GIS, and UAV. Lastly, this approach is applicable for areas that have clear master plan and complete geological information.

5 Conclusions

Due to the lack of relevant research on excavated soil and construction sludge production, this study has presented an approach to quantify excavated soil and construction sludge. In this approach, urban topographic map should be referred to first to divide the city into different areas according to the terrain. Geological survey reports of each area should be then used to classify the excavated soil and construction sludge. Subsequently, based on the urban master plan, the city’s construction land area should be estimated through RS. The excavated soils and construction sludge production per unit land area in each area should be calculated through site investigation. Our approach is based on classification and can deliver reliable and dynamic results. The classification and quantification of excavated soils and construction sludge can provide a basis for planning of disposal facilities and a reference for proper disposal and recycling of the construction wastes, leading to sustainable management of construction wastes.

The Wenzhou case was introduced to illustrate the approach’s general applicability. The estimation results showed that in the next five years (2021–2025), 107.5 × 10⁶ m³ of excavated soils and 81.7 × 10⁶ m³ of construction sludge would be generated in Wenzhou. In regard to classification, the excavated soil was classified into four types: miscellaneous fill (20.2 × 10⁶ m³, 19%), crust clay (15.2 × 10⁶ m³, 14%), muddy clay (31.1 × 10⁶ m³, 29%), mud with silty sand (41.0 × 10⁶ m³, 38%), while the construction sludge was classified into two types: liquid sludge (71.5 × 10⁶ m³, 88%), paste-like sludge (10.2 × 10⁶ m³, 12%).

References

[1] Zhang N, Duan H, Sun P, Li J, Zuo J, Mao R C, Liu G, Niu Y N. Characterizing the generation and environmental impacts of subway-related excavated soil and rock in China. Journal of Cleaner Production, 2020, 248 : 119242

[2] TheU.S. Environmental Protection Agency. Characterization of Building-related Construction and Demolition Debris in the United States. Report No. EPA530-R-98-010. 1998

[3] WRAP. Guidelines for Measuring and Reporting Construction, Demolition and Excavation Waste. 2010

[4] KatsumiT. Soil excavation and reclamation in civil engineering: Environmental aspects. Soil Science and Plant Nutrition, 2015, 61(Suppl 1): 22–29

[5] Kamon M, Katsumi T, Imanishi H. Utilization system of waste slurry from construction works. Bulletin of the Disaster Prevention Research Institute, 1993, 43( 4): 73–89

[6] Kupusamy K, Nagapan S, Abdullah A H, Kaliannan S, Maniam H. Construction waste estimation analysis in residential projects of Malaysia. Engineering, Technology and Applied Science Research, 2019, 9( 5): 4842–4845

[7] Qiao L, Liu D D, Yuan X, Wang Q, Ma Q. Generation and prediction of construction and demolition waste using exponential smoothing method: A case study of Shandong province, China. Sustainability, 2020, 12( 12): 5094–5105

[8] Lu W S, Lou J F, Webster C, Xue F, Bao Z K, Chi B. Estimating construction waste generation in the Greater Bay Area, China using machine learning. Waste Management, 2021, 134( 10): 78–88

[9] Cochran K, Townsend T, Reinhart D, Heck H. Estimation of regional building-related C&D debris generation and composition: Case study for Florida, US. Waste Management, 2007, 27( 7): 921–931

[10] Llatas C. A model for quantifying construction waste in projects according to the European waste list. Waste Management, 2011, 31( 6): 1261–1276

[11] Li J, Ding Z, Mi X, Wang J. A model for estimating construction waste generation index for building project in China. Resources, Conservation and Recycling, 2013, 74( 5): 20–26

[12] Ding Z K, Liu R S, Wang Y F, Tam V W, Ma M X. An agent-based model approach for urban demolition waste quantification and a management framework for stakeholders. Journal of Cleaner Production, 2020, 285( 2): 124897

[13] Huang S L, Hsu W L. Materials flow analysis and emergy evaluation of Taipei’s urban construction. Landscape and Urban Planning, 2003, 63( 2): 61–74

[14] Rosado L, Niza S, Ferrão P. A material flow accounting case study of the Lisbon metropolitan area using the urban metabolism analyst model. Journal of Industrial Ecology, 2014, 18( 1): 84–101

[15] Guo D M, Huang L Z. The state of the art of material flow analysis research based on construction and demolition waste recycling and disposal. Buildings, 2019, 9( 10): 207–217

[16] Gao X F, Nakatani J, Zhang Q, Huang B J, Wang T, Moriguchi Y. Dynamic material flow and stock analysis of residential buildings by integrating rural-urban land transition: A case of Shanghai. Journal of Cleaner Production, 2020, 253( 4): 119941

[17] Wu H, Wang J, Duan H, Ouyang L, Huang W, Zuo J. An innovative approach to managing demolition waste via GIS (geographic information system): A case study in Shenzhen city, China. Journal of Cleaner Production, 2016, 112 : 494–503

[18] Kataguiri K, Boscov M, Teixeira C E, Angulo S C. Characterization flowchart for assessing the potential reuse of excavation soils in Sao Paulo city. Journal of Cleaner Production, 2019, 240 : 118215

[19] Kamon M, Katsumi T, Inui T. Dehydration-solidification treatment and geotechnical utilization of waste sludge from construction works. Environmental Geotechnics, 1998, 603–608

[20] Kamon M, Inazumi S, Rajasekaran G, Katsumi T. Evaluation of waste sludge compatibility for landfill cover application. Journal of the Japanese Geotechnical Society Soils & Foundation, 2002, 42( 4): 13–27

[21] Katsumi T, Kamon M, Inui T. Japanese status on the use of waste and by-products in geotechnical applications. recycled materials in geotechnics. Sessions at ASCE Civil Engineering Conference & Exposition, 2005, 22–41

[22] JapaneseMinistry of Land. Ministerial Ordinance for Determining the Standards of Judgment Concerning the Use of Recycled Resources for Persons Engaged in Construction Business. 2001 (in Japanese)

[23] Mori M, Takahashi H, Ousaka A, Horii K, Kataoka I, Ishii T, Kotani K. A proposal for a new recycling system for high-water content muds by using paper debris and polymer and strength property of recycled soils. Journal of the Mining and Materials Processing Institute of Japan, 2003, 119( 4): 155–160

[24] Takahashi H. State-of-the-art and future problems of countermeasures for excavated soils discharged from excavation construction. Micro-Tunneling Technology, 2006, 20( 4): 3–8

[25] Yamazaki J, Takahashi H, Kanari H, Mori M. An experimental study on production of planting soil from the viewpoint of soil physical properties. Journal of the Mining and Materials Processing Institute of Japan, 2008, 124( 12): 818–823

[26] Gulsen F, Inui T, Kato T, Takai A, Katsumi T. Numerical investigation on utilization of natural contaminated soil in the embankments. In: Proceedings of the 8th International Congress on Environmental Geotechnics. Singapore: Springer, 2018, 466–473

[27] Meda S R, Sharma S K, Tyagi G D. Utilization of waste sludge as a construction material—A review. Materials Today: Proceedings, 2021, 46( 9): 4195–4202

[28] Murakami O, Masuda T, Hanada O, Tamura T, Kamao S. Recycling and treatment of construction sludge. WIT Transactions on Ecology and the Environment, 2012, 155 : 1129–1138

[29] Takahashi H. Topical Themes in Energy and Resources. Tokyo: Springer, 2015, 177–194

[30] Magnusson S, Lundberg K, Svedberg B, Knutsson S. Sustainable management of excavated soil and rock in urban areas—A literature review. Journal of Cleaner Production, 2015, 93( 4): 18–25

[31] Yamana M, Tomizawa Y, Fujiwara T, Mizuta K, Mizuno K, Inui T, Katsumi T, Kamon M. Management of the Soils Discharged from Shield Tunnel Excavation. In: Proceedings of the 8th International Congress on Environmental Geotechnics. Singapore: Springer, 2018, 374–381

[32] Katsumi T, Inui T, Yasutaka T, Takai A. Towards sustainable soil management—Reuse of excavated soils with natural contamination. In: Proceedings of the 8th International Congress on Environmental Geotechnics. Singapore: Springer, 2018, 99–118

[33] WenzhouPlanningNaturalResources Bureau. Master Plan of Wenzhou City (2021–2025). 2017 (in Chinese)

[34] WenzhouPlanningNaturalResources Bureau. Master Plan of Wenzhou City (2016–2020). 2012 (in Chinese)

[35] WenzhouMunicipal People’s Government. Notice of the Office of WenzhouMunicipal People’s Government on Printing and Distributing the Three Year Action Plan for Major Construction Projects in Wenzhou (2016–2018). 2016 (in Chinese)

[36] WenzhouMunicipal People’s Government. Short Term Construction Planning of Wenzhou Urban Rail Transit (2020–2026). 2019 (in Chinese)

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