Research on Risk Assessment of Expressway Project under PPP Mode

: On the basis of literature survey, this paper combines qualitative research with quantitative research to evaluate the influencing factors of expressway project risk under PPP mode. This paper starts from three parts:Firstly, starting from the current situation of expressway construction projects at home and abroad through the analysis of the advantages and disadvantages of PPP mode and three characteristics, the necessity and importance of project risk management under PPP mode are obtained. Secondly, the paper elaborates the risk of PPP project of expressway identifies the corresponding risk, and initially determines the three major factors affecting the risk of expressway project under PPP mode. Finally, according to expert judgment, the most critical factor is determined and a scientific, reasonable and effective risk factor evaluation index system is established. The index system includes three first - level indicators and six second - level indicators. On this basis, the judgment matrix is constructed by using the analytic hierarchy process, so as to form the influencing factor model. Finally, taking Fuling Fengdu Expressway in Chongqing as an example, this paper uses the analytic hierarchy process (AHP) to carry out an empirical study on the model, in order to determine the importance of different risk factors.


Highway Profile
Chongqing fuling-fengdu expressway is an important part of chongqing expressway network, it belongs to the "ten arrows" part of the "three rings ten radiations three lines" skeleton highway network in "chongqing expressway network planning. Along the route of this project, there are chongqing, fuling, qingxi, nantou, zhanpu, fengdu and shuanglu. According to the highway two-way four-lane standard to build, a total of 46.5 km,the total investment is 4.179 billion yuan [1]. Figure 1 is the highway route map from fuling to fengdu [2]. 1 Figure 1. The highway route map from fuling to fengdu.

Adopt BOT+EPC Mode
The public sector issues special admissible management authority to the private sector, while the private sector controls and contracts the project by using the general contracting mode during the specified construction period of the project. Once the admissible period of the government expires, the management authority of the facility is in the hands of the government.

Project Implementation Program
The management of the project is in the hands of private organizations, which are allowed to collect administrative fees for a period of 30 years. Project financiers have the right to collect vehicle tolls and to manage within the jurisdiction of the high speed. The government said: "The public sector will severely rectify the emergence of other management methods caused by poor construction." The Chongqing Municipal People's Government has promised to introduce corresponding convenience measures and substantive priority to ensure a smooth return of the profits of the contractor. The Chongqing Municipal Government agreed to provide policy support to the contractor, provide reputation guarantee for its financing, and ensure a good social environment during the construction of the project.

3
Case Analysis

Build a Hierarchy
According to a large number of literature and expert evaluation, using the analytic hierarchy process (ahp) concluded that target layer is the PPP mode of project risk evaluation, criterion layer from the construction risk, cooperation risk, environment risk, nature, society, the design and construction are obtained, such as cost, negotiation and cooperation risk index layer, construct of the highway of chongqing fuling to video class hierarchy, as shown in table 1. Define the factor indicator as set X, X= (X1, X2... I = 1,2... , n). Therefore, the influential factor sets are as follows: X={ X1， X2， X3 }， X1={ X11， X12}， X2={ X21， X22 }， X3={ X31， X32 }.

Specific Calculation Process
According to expert rating and 1-9 scale method [3], the weights are determined from three aspects of environmental risk, construction risk and cooperation risk, as shown in table 2, table 3, table 4, table 5, table 6  and table 7. I is as important as j 3 I is slightly more important than j 5 I is more important than j 7 I is much more important than j 9 I is absolutely more important than j 2 、 4 、 6、8 It is between the two adjacent judgment scales mentioned above The bottom If the importance ratio of I to j is λ, then the importance ratio of j to I is 1/λ

Total Hierarchical Ordering
For the target layer, the index Cj [4] contained in the criterion layer Bi is calculated as follows: W=W Bi × W C j (1) According to the weights W1, W2 and W3, the following weight table is obtained, as shown in table 8. Consistency check: Suppose that the consistency index of some factors in layer N to the J elements in layer N-1 is CIj (k) , and the average random consistency index is RIj (k) .

(3)
When CR (k) ≤0.10, it shows that the results of the total ranking are consistent [5]. From the above weight table, we can see that CI1 = 0.013,CI2 = 0.018, RI1 = 0, RI2 = 0, because the judgment matrix with the order less than or equal to 2 has complete consistency, so there is no need for consistency test [6], therefore, (4) So, the judgment matrix has the whole consistency.

Evaluation Results
Therefore, it can be known from the above calculation that the consistency of all judgment matrices has passed the test, and the single-level ranking result is the overall ranking result. The specific analysis results are as follows: Among the influencing factors of expressway risk projects under PPP mode, the proportion of cooperation risk is the highest, followed by construction risk, and the proportion of environmental risk is the lowest.
Among environmental risk factors, the proportion of natural environment and social environment is equal, so it is the main influencing factor for chongqing fuling-fengdu expressway project. During the construction of the project, it is necessary to make early preparation, take preventive and remediation measures against uncontrollable factors such as topography, geology and weather, timely communicate with the government, and implement land expropriation and demolition and related policies.
In the construction risk, the weight of design is equal to that of construction risk and cost risk, so it is also an important influencing factor. In the whole process of project construction, design, construction and other processes should be strictly controlled to prevent or prevent the occurrence of risk factors as early as possible, so as not to cause unnecessary losses.
The proportion of credit risk is relatively large and the negotiation risk is relatively low, which indicates that during the cooperation period of this project, the government should prevent the contractor from exaggerating its own strength in order to obtain the right of management. At the same time, the chongqing government also needs to keep its promise to avoid losing credibility with the public, so the policies should be timely made public and reviewed by the public.

Epilogue
On the basis of consulting a large number of documents and case studies, this article starts with the relevant theory of PPP model, expounds the basic steps of project risk management, and makes a preliminary identification of the risks of expressway projects under PPP model, using Chongqing Fuling to Fengdu Expressway As an example, the main risk factors of the project were obtained through the establishment of a model and analysis, and the study of risk management analysis was conducted, and the following conclusions were obtained: Based on the principle of holism and omnibearing, based on the basic theory of the PPP model, the analysis of the highway project under this model shows that the hidden risk factors in the project are very complicated. According to the different degrees of project risk sources, project risks are classified into systematic risks and nonsystematic risks. Systemic risks include political risks, financing risks and force majeure risks; non-systemic risks include construction risks and cooperation risks.
Taking Fuling Fengdu Expressway in Chongqing as an example, it can be seen that cooperation risk is the main risk of the project, followed by construction risk, and the weight value of environmental risk is the least. According to the inspection, the direction that the project should be strictly controlled in the construction process is defined, that is, the government and all parties involved should abide by their commitments and jointly undertake the possible problems during the construction of the project.
This study not only verifies the practicability and scientificity of AHP, but also judges the risk factors that may exist in the process of expressway construction, providing scientific guidance for the construction of Expressway under PPP project in China, and provides a new idea and optimal design for scientific risk sharing.