The Peshawar-Karachi Motorway (Sukkur-Multan Section) implemented by China State Construction Engineering Corporation Co.Ltd.is the largest transport infrastructure project under construction based on EPC mode. The PKM (Sukkur-Multan Section) project is a six-lane bi-directional motorway of 392km, with a cost of USD 2.9 billion. It’s the flagship project under CEPC, and has been completed. Focusing on the technical management of large-scale overseas motorway infrastructure projects on EPC mode, this paper makes the following technical summary according to the characteristics and implementation of this project.
The Technical Management Characteristics of the Project
1.1 Management of Construction Schemes
Due to the long route of the PKM project, a HQ and seven sections were established, and the Employer and the third-party consultancy company also conduct their management according to this kind of establishment. The HQ of the project formulated a unified format for construction schemes. The construction schemes were reviewed and approved both internally and externally to ensure they are simple and easy, convenient, economical and safe, and that the construction quality is secured.
1.2 Implementation of standards
Based on both local and Chinese standards, many manuals and guidelines for standardized construction and acceptance were formulated, including the Standard Guidelines for Construction Scheme of CSCEC Pakistan PKM (Sukkur-Multan Section) Project, the Standard Guidelines for Deflection Testing of Subgrade and Pavement, the Standard Manual for Tests, the Standard Procedures for Acceptance of Materials, the Standard Guidelines for Acceptance of Prefabricated Girder Yards, etc.
1.3 Trial sections before large-scale construction
Before each item of works was implemented at large scale, the trial section had been executed and tested for acceptance, then a summary on its construction methodology was made and approved.
1.4 Overall testing management
A total of seven test laboratories were established along the entire alignment, and a central test laboratory was established at the HQ. The HQ conducted unified management on them, including planning, allocation of instruments and equipment, calibration and implementation of SOP for testing. The central test laboratory at the HQ carried out major checks and supervision for all kinds of main construction materials and the mix design.
1.5 On-site technical services
For the on-site difficulties in technologies and methodologies at sections, senior professional and technical personnel were dispatched by the HQ to tackle them in a timely manner. For key construction methodologies, major technical difficulties and problems at site and major on-site special safety schemes, the HQ would organize technical groups and safety technologists to hold seminars and review meetings for resolutions.
- Management of Overseas Technical Staff
Overseas technical staff consisted of Chinese and Pakistani technicians, with the former as primary technical forces and the latter for ancillary works and assisting external communication. The division of jobs is seen as below:
| Sr.No. | Staff | Division of Jobs |
| 1 | Chinese technical staff | primary technical forces of the project |
| 2 | Pakistani technical consultants | Experienced, familiar with Pakistani specifications and construction technologies, provide professional technical advice and coordination with the Employer as senior technicians |
| 3 | Pakistani technical staff | technical assistance |
- Differentiated Management of Technologies
| Differences | China | Pakistan | Countermeasures |
| Technical standards | Chinese standards, which are systematical and have strong guidance for construction | Pakistani, European and American standards, which are slow in updating, unsystematic and difficult for reference. | Based on the Contract, appropriate technical indicators were selected by fully comparing the design standards of China, America and Pakistan, combining the characteristics of the project and taking into account factors such as safety, economy and the local style. |
| Review and approval of construction schemes for risky and major works | Expert review is required | Reviewed by the Consultant. Expert review is not required. | The expert panel was established to conduct expert review on risky and major works. After the review was passed, the construction schemes would be submitted to the Consultant for review to ensure safe construction. |
| Construction methodologies and practices | The machinery and equipment are advanced and complete, and new technologies and methodologies are widely used. | As the country is economically backward, the machinery and equipment level is low, and the updating of technological standards is slow, which restrict the promotion of new technologies and methodologies. | Based on the experience and recommendations of local technical consultants, local practices were studied, and at the same time, advanced construction equipment and methodologies in China were introduced according to the features of the project. |
| Language and communication | No language issue. | The Contract and standards are all in English, and the English level of local people is different, thus creating deviations in understanding. | Pakistani technical consultants were employed to better understand local specifications, and professional Chinese translators were also employed. |
- Differentiated Management of Standards
By fully comparing the design standards of China, America and Pakistan, combining the characteristics of the project itself and taking into account the factors such as safety, economy and the local style, appropriated technical indicators were selected to design a safe, economical and comfortable motorway in harmony with the environment along the alignment.
The contractual basis for the integration of standards: the Framework Agreement between the governments of China and Pakistan: the design of the project shall follow the Chinese technical standards while comprehensively considering the relevant standards and practices of Pakistan; the Loan agreement: the relevant Chinese standards shall be followed, whereas according to the relevant clauses of the Contract, the pavement design and the structural design of the project shall refer to the American specification and the General Specifications of Pakistan. Therefore, it would be hard to execute the project by simple use of the Chinese specifications.
The technical basis for the integration of standards: the existing Pakistani specifications have not been updated for 20 years and they are systematically unsound. In addition, the climate characteristics and geological conditions of America are quite different from those of Pakistan. Therefore, it needs to be verified whether these specifications are fit for application.
In the actual selection of specifications, full consideration was given to the local climate, geological environment, the characteristics of road construction materials along the alignment as well as the advantages and disadvantages of the specifications of China, America and Pakistan, which were fully integrated and applied. In the meanwhile, each standard was reviewed and verified during the design and implementation process. The principles for selection of technical standards are seen as follows:
Table 01: The principles for selection of technical standards
| Sr.No. | Status of standard selection | Principles for standard selection | Case description |
| 1 | when the Chinese, American and Pakistani standards are similar or complementary to each other | In the design process, the specific requirements of the three countries were studied in detail. According to the actual situations at the site, the American and Pakistani standards were adopted for design, and the Chinese standards were used for review and verification. | As for the design of the bridge pile foundation, under the same geological conditions, the bearing capacity of pile foundation was calculated and the load was calculated by the component coefficient method by adopting the American specifications. The corresponding pile length was verified by the load test, and the bearing capacity and settlement were acceptable, and met the requirements of the specifications. At the same time, the Chinese specifications were adopted to calculate the allowable bearing capacity and pile length of a single pile. Through the comparison and checking calculation, the calculated pile lengths were basically the same. Therefore, the American and Pakistani specifications were applied for calculation of the pile foundation, and the Chinese specifications were adopted for review and verification. |
| As for the design of the pavement structure, the American standard AASHTO (1993) was adopted for the design calculation, and the Chinese standard was applied for verification. In the American standard, the main testing indexes for pavement quality are compaction degree and IRI, while the deflection is tested for acceptance for quality control in the Chinese standard. Therefore, double standards were applied for the pavement quality control on this project to ensure the design and construction quality of the pavement. | |||
| 2 | when the Chinese, American and Pakistani standards conflict with each other | Studies and demonstrations are necessary to select appropriate indicators according to actual situations of the project. | As for the design load of bridges, the Chinese standard adopts highway grade I load, while the Pakistani standard adopts grade A /AA load, and the American standard adopts HL-93. There is a big difference in the load of these standards. According to the actual situations, the Pakistani standard of Grade A /AA load was adopted, and the American standard of HL-93 load was adopted to check the calculation. |
| 3 | when the specifications are not included in the Chinese, American and Pakistani standards | During the design process, detailed investigations were conducted on the actual situations at site . And the relevant technical standards were creatively proposed through experiments and researches. | As for the dynamic stability index of asphalt concrete under high temperature and heavy load conditions, the local temperature is high, with the atmospheric temperature reaching 49 ° C, and the road temperature up to nearly 80 ° C. Besides, there was a large volume of traffic and heavy duty vehicles. This climatic condition is not seen in China and America, where the technical design standards under similar conditions do not exist. According to the local climate features, the project proposed the technical standards for anti-rutting of asphalt mixture under the high temperature environment: rutting at asphalt sub-base ≥1500 times /mm (70℃), rutting at asphalt base ≥3200 times /mm (80℃), and rutting at asphalt wearing course ≥3200 times /mm (80℃). |
Table 02: Selection of Main Design Standards
| Sr.No. | Design item | Chinese design standards | American and Pakistani design standards | Studies on their differences | Selection of standards |
| 1 | Geometric Design of Alignment | Design Specification for Highway Alignment JTG 020-2017 | AASHTO: Geometric Design of Highways and Streets (2011) | The Chinese and American design standards are different in major indicators such as the radius of circular curve, super-elevation, easing curve, etc. The American road design theory and system focus more on the coordination and harmony between routes and terrain and environment. | The American design standards were selected, and the higher standard was selected for the differences between the Chinese and American standards. |
| 2 | Pavement design | Specifications for Design of Highway Asphalt Pavement JTGD50—2017 | AASHTO: Guide for Design of Pavement Structures (1993) | The main design indexes in the Chinese standards are road surface deflection and tensile stress of asphalt surface or base course. The design indexes of AASHTO are fatigue cracking and low temperature cracking of asphalt layer, longitudinal cracking of asphalt layer, fatigue cracking of inorganic binder structure layer, rutting and roughness. The index of road surface deflection is a particular index of the Chinese standards. | The Chinese standard was selected for design, and the American standard was selected for checking. |
| 3 | Structural design of bridges and culverts | General Code for Design of High Bridges and Culverts JTG D60-2016 | AASHTO: LRFD | The Chinese and American specifications for bridges mainly differ in design methods, values of vehicle loads, load combination coefficients, basic calculation assumptions and expressions of sectional deflection capacity, and sizes and guarantee rates of concrete standard specimens. | The American standards were selected for design, and meanwhile based on the local design habits of Pakistan, monolithic piles were applied for piers and simply supported I-beam bridges were applied. |
| WPCPHB: Practical Guide for Motorway Bridges in Pakistan (1967) | |||||
| AASHTO: Standard Specifications for Highway Bridges (2004) |
The selection of main technical indicators has a great impact on the difficulty level of construction activities and the quality of roads. Therefore, all-round comparative studies were made on main indicators in the Chinese and Pakistani standards, which were then integrated accordingly. Based on the climate, geology, traffic and construction conditions of the project area and taking into consideration such factors as economy, construction period and quality, etc., the control indicators of construction suitable for this project were selected and finalized. The integration of main indicators is shown in the following table:
Table 03: Integration of Main Technical indicators
| Sr. No. | Item | Indicator | Chinese Standards | Pakistani Standards | Selection of Standard Indicators | |
| 1 | subgrade | Compaction degree (%) | Upper roadbed | ≥96 | ≥95 | The project is mostly located in the area with silty soil and fine sand, and the silty soil is difficult to be compacted, therefore, the Pakistani standards with lower requirements were adopted for compaction degree of the subgrade. At the same time, the compaction degree of the sand-filled subgrade is increased to 93% to reduce settlement after construction. |
| Lower roadbed | ≥94 | ≥93 | ||||
| Upper embankment | ≥93 | Soil filling≥90 | ||||
| Lower embankment | ≥93 | Sand filling≥93 | ||||
| testing frequency for compaction | 2 points are tested every 1000㎡ | 1 point is tested every 200m（≥7000m2） | In order to ensure the compaction degree of subgrade under control, one test point was selected every 50m based on the Chinese and Pakistani standards. | |||
| 2 | graded gravel layer | Compaction degree (%) | Sub-base | ≥97 | ≥98 | Since this motorway was designed for heavy traffic load, the Pakistani standards with higher requirements was selected in order to improve the strength and stiffness of the pavement, enhance the bearing capacity of the pavement, reduce the deformation in later stages and reduce the possibility of rutting caused by heavy load. |
| Base course | ≥99 | ≥100 | ||||
| CBR（%） | Sub-base | ≥100 | ≥50 | Based on the quality of local rock materials, and given the Chinese and Pakistani standards, it was decided that the CBR of sub-base≥80 and the CB Rof base course≥100 to ensure the bearing capacity of the graded gravel layer. | ||
| Base course | ≥180 | ≥80 | ||||
| compacted thickness | 16cm~20cm | ≤15cm | Verified through trial sections and approved by the Employer, the compaction thickness for graded gravels followed the Chinese standard so as to improve the construction efficiency. | |||
| 3 | Asphalt pavement | Compaction degree (%) | ≥98 | ≥97 | In order to reduce deformation of the asphalt pavement at later stages and improve the rutting resistance, the Chinese standard with higher requirements was followed. | |
| dynamic stability (number/mm) | Testing temperature 60℃ | No requirement in Pakistan. The American standard testing temperature is 60℃. | High temperatures continued from March to October in Pakistan, with the highest temperature of the road surface up to 78 °C. Therefore, we broke through the Chinese and American standards. In order to improve the rutting resistance, the testing temperature of the ordinary asphalt mixture was 70 ° C, and the dynamic stability was not less than 1500 times /mm, the testing temperature of the modified asphalt mixture was 80 ° C, and the dynamic stability was not less than 3200 times /mm. | |||
| 4 | roadbed top, road surface | Deflection (0.01mm) | Follow the design requirements | No requirement. | Deflection testing is not required in the General Specifications of Pakistan. To control the construction quality of the subgrade and pavement in a better way to further ensure the strength and stiffness of the subgrade and pavement, we brought forward the requirements for testing of deflection at different levels of the subgrade and pavement with reference to the Chinese standards. And the QC/QC team at the HQ was responsible for the testing and acceptance which covered the whole alignment to have ensured the actual bearing capacity of the subgrade and pavement. | |
| International Roughness Index (IRI) | IRI≤2.0m/km | IRI≤1.2m/km, IRI≤1.5m/km after 3 years of DNP | The Pakistani standards were followed. | |||
- Application of New Methodologies and New technologies
A number of mature new methodologies and technologies commensurate with local conditions were adopted according to the characteristics and contractual requirements of the project.
5.1 Application of the spiky roller and the impact roller
Since most of the subgrade was filled with the low liquid limit clay, it is very difficult for compaction. The spiky roller was used in compaction of different layers to raise the compaction degree. At the same time, in order to improve the overall strength and stiffness of the subgrade and reduce the settlement after construction, the impact roller was used each time when the subgrade was filled with a thickness of 30cm-50cm to reinforce the subgrade.
5.2 The construction methodology for sand-filling subgrade
Since the project is located in the plain, and the lands along the alignment are farmlands, it was required that the depth for soil borrow shall be less than 1 meter. Moreover, the filling along the alignment was low liquid limit clay, which was difficult to be compacted. These posed a great impact on the effect of the subgrade construction. In order to speed up the construction efficiency of the subgrade, the sandy soil along the alignment was used as much as possible as the filling material of the subgrade, the outer side slope of the subgrade was covered with clay, and the drainage pipes or gravel blind ditches were arranged at the foot of the slope to form a drainage channel. For homogeneous and clean sandy soil, the watertight construction method was adopted, and for unhomogeneous sandy soil containing clay, the construction method of optimal water content rolling was adopted.
5.3 Improvement of the filling materials for the upper roadbed
The CBR of the clay in the entire alignment of the project was about 5%-8%. In order to ensure that the deflection of Zone-95 of the upper roadbed met the design requirements, the CBR of the Zone-95 of the upper roadbed shall be increased to 20%. Therefore, different technical schemes for improvement were adopted for filling materials with different strengths in different sections. The powder clay, natural sand and gravels were mixed in different proportions. They were first mixed outside of the alignment, then transported on the alignment for spreading and mixing, and were finally compacted after fully mixed.
5.4 Improvement of the IRI of the pavement
The International Roughness Index (IRI)of the wearing course specified in the Contract was less than 1.2m/km, which was much higher than other international standards (IRI≤2.0 in the Chinese standards, IRI≤2.0 in the Spanish standards , IRI≤1.4 in the Swedish standards). It constituted a technical difficulty for the project construction, and the cost for rework of the asphalt pavement was very high. In the paving process of different structural layers, pavers with thread-drawing were applied to lay the graded gravel sub-base, base course and gravel asphalt base course to ensure flatness, thickness and elevation. Moreover, the frequency and amplitude of pavers’ rammer for the lower asphalt base course and the upper asphalt base course to improve the initial compaction rate of paving.The balance beam method was adopted for laying of the wearing course, and static pressing and light pressing were mainly used. The number of rolling passes of the pneumatic tires was increased for each layer to improve the flatness. In the laying and rolling process of the asphalt pavement, 5-meter straightedges were used to enhance the testing and control of roughness, and the laser roughness testing instruments were applied for testing of the finished pavement.
5.5 Application of the slip form construction methodology for New Jersey Barriers and curbs
Due to the long project alignment, the construction methodology of slip form was adopted for New Jersey Barriers and curbs. The key points of the slip form methodology were optimization of the concrete mix ratio, adjustment and control of the slump of concrete at site. At the same time, we changed the way of unloading the materials to have solved the difficulty in slip form construction under the high temperature environment. This construction methodology have multiple advantages such as quick construction speed, good alignment and appearance and low construction cost.
- Technical Difficulties for the Project Safety
6.1 Installation of prefabricated girders of the small-angle skew bridges
There were eight bridges (a single span is 30m long) in 23 degree intersection with the main carriageway, and seven bridges (a single span is 30m long) in 25 degree intersection with the main carriageway. The intersection angle was very small. When the bridge girder erection machine was used for installation of prefabricated girders, the vertical spacing of the longitudinal main girders on both sides of the bridge girder erection machine was reduced from the normal spacing, due to which the bridge girder erection machine was prone to lost stability transversely. Meanwhile, the force situation of the various components such as the front leg of the bridge girder erection machine and the crane leg would also change greatly, which would pose many unsafe factors to the overall horizontal movement of the machine and the longitudinal movement of the crane. According to the spacing between the main beams of the bridge erection machine, the stability checking calculation was carried out, and the crane and the main driving rear fulcrum rail machine was modified and widened. The front leg and the crane leg were reinforced, and the overall transverse and longitudinal stability of the bridge erection machine was checked again.
6.2 Construction of inverted awl shell water towers
The service areas along the whole alignment were designed with the inverted awl shell water towers, which mainly consisted of three parts: the foundation, the barrel body and the water tank. The cast-in-place methodology was applied for construction of water towers. It was relatively difficult for the construction safety assurance. The scaffold would be set up at a high height, and was used as a formwork support, which needed to withstand the combined forces of self-weight, wind load, formwork load, reinforced concrete load and construction load. These posed a very high requirement on the bearing capacity and stability of the whole framework. In order to ensure safety, we enhanced the checking of the construction scheme of the scaffold and the erection requirements. The bracket formed a “#” shape around the barrel body, and the rigid connection rod was set up with the barrel body. The scaffold was set up in strict accordance with the requirements of the construction scheme and relevant specifications, and the transverse connection rod was added according to the actual situation at the site.
- Recommendations in the Technical Management
The Pakistani survey engineers have the limited technical expertise, and are far less diligent and dedicated than the Chinese engineers, therefore, they cannot be completely relied on for survey control. It’s recommended that the surveys activities be incorporated into the management by the HQ, and that the position of the professional Chinese survey engineer be arranged to monitor and control the survey activities at the site.
