CN106156343B

CN106156343B - Deep foundation pit construction scheme safety evaluation knowledge base and automatic safety evaluation method

Info

Publication number: CN106156343B
Application number: CN201610578011.7A
Authority: CN
Inventors: 宫培松; 郭海湘; 於世为
Original assignee: China University of Geosciences
Current assignee: China University of Geosciences
Priority date: 2016-07-21
Filing date: 2016-07-21
Publication date: 2020-02-18
Anticipated expiration: 2036-07-21
Also published as: CN106156343A

Abstract

The invention discloses a deep foundation pit construction scheme safety evaluation knowledge base and an automatic safety evaluation method. The knowledge base carries out scientific and orderly storage and management on all relevant knowledge required by the safety evaluation of the deep foundation pit engineering construction scheme, so that the safety evaluation work eliminates the uncertainty brought by the current manual evaluation, and the evaluation result with stable quality and space-time information is obtained in a short time to support the field safety management. The method can be used for managing the safety review knowledge of the construction scheme of the deep foundation pit, realizes automatic safety review, overcomes the practical difficulty in the construction scheme safety review in the construction preparation period at present, improves the quality and efficiency of the safety review work of the construction scheme of the deep foundation pit, and provides better decision support for the safety management in the future construction period.

Description

Deep foundation pit construction scheme safety evaluation knowledge base and automatic safety evaluation method

Technical Field

The invention belongs to the field of engineering risk identification, and particularly relates to a deep foundation pit construction scheme safety review knowledge base and a safety review method thereof.

Background

Deep foundation pit engineering has very high safety risk, and the incident takes place occasionally. According to the regulations in the "safety management method for the project with high risk of parts and items" (No. 2009] 87), before construction, the construction scheme of the deep foundation pit project must be subjected to safety review by an expert committee, and if the review fails, the construction cannot be started. The safety evaluation of the deep foundation pit construction scheme is an important link of the construction safety management of the deep foundation pit and is also a starting point of the construction safety management of the whole deep foundation pit engineering.

At present, the construction scheme safety evaluation work of the deep foundation pit in China is mainly carried out by reporting the construction scheme by a construction unit and establishing an expert group by a local construction administrative department. In actual work, there are the following difficulties.

(1) The manual review can not ensure complete accuracy and the working efficiency is lower

The safety evaluation work of the deep foundation pit engineering construction scheme is theoretically understood to be based on the deep foundation pit engineering construction scheme information to carry out safety risk evaluation, and the safety evaluation is a name for actual work and is consistent with the safety risk evaluation in theoretical meaning. The construction scheme of the deep foundation pit engineering is the basis of evaluation work, comprises a plurality of technical files, takes open cut deep foundation pit engineering as an example, and the evaluation basis comprises the following steps: the construction method comprises the following steps of designing all necessary technical files of various deep foundation pit professional construction schemes (excavation schemes, precipitation schemes, monitoring schemes and the like), geological survey reports, foundation pit design drawings, meteorological data and the like of the deep foundation pit engineering.

At present, the safety evaluation work is manually completed by an expert group. The expert group firstly reads key technical information in the construction scheme, analyzes the safety risk in the construction period and evaluates the risk level by using the experience of the expert group for carrying out construction work of the deep foundation pit for many years, provides corresponding prevention and control measures, and receives review again after the construction scheme which does not meet the safety requirement is modified, and the scheme which does not pass the review can not be implemented.

The analysis of the safety risk is the main content of the evaluation work, and a large amount of safety evaluation knowledge of the deep foundation pit engineering construction scheme is required. The safety review knowledge can theoretically be expressed as a series of rules in the form of "… … results if there is … … premise". The security risk is affected by risk factors, and the security risk event is caused by several risk factors, these two sets of relationships may also be expressed as "… … security risk if there is an … … risk factor condition" and "… … security risk event may occur if there is a … … risk factor condition".

Suppose a security risk is associated with m risk factors, the ith risk factor having n_iA possible value, such a security risk corresponds to

Each risk factor value combination represents a possible working condition, namely a review rule. Assuming that risk factors and values of the safety risk are scientific and reasonable, then

The combination of the risk factors includesAll review rules for security risks.

Taking the safety risk of "water and sand gushing at the bottom of the foundation pit" as an example, it is assumed that the safety risk is at least related to 6 risk factors, which are respectively: underground water condition, foundation pit bottom soil quality, enclosure structure soil penetration ratio, foundation pit internal and external water head difference, foundation pit bottom reinforcement condition and enclosure structure rock penetration condition. Each risk factor at least comprises 2 possible values (such as the rock entering condition of the building envelope), and some of the risk factors reach more than 5 values (such as the foundation pit bottom soil property). Thus, the combination of the risk factors of the security risk easily exceeds 1000, i.e., the review knowledge of the security risk is expressed by thousands of review rules. The deep foundation pit engineering construction comprises three construction methods of open excavation, cover excavation and underground excavation, and the construction safety risk under each construction method is numerous. Therefore, the safety review knowledge of the construction scheme of the deep foundation pit engineering is huge.

The safety review knowledge of the deep foundation pit engineering construction scheme is huge, and no document or patent comprehensively summarizes the types of the safety risks of the deep foundation pit engineering construction and the corresponding risk factors so far. More importantly, the deep foundation pit engineering construction safety risk assessment knowledge is not expressed in a unified and standard mode, so that various different angles and methods exist for evaluating the safety risk, and the quality stability of the current assessment work is influenced. The experts participating in the review process cannot completely master the information with such orders of magnitude, so that the review result is not completely accurate, and in addition, the review work consumes a lot of time due to the large information processing amount in the risk analysis process, and the efficiency is low.

Summarizing, manual review has the difficulty of poor accuracy and low work efficiency.

(2) Lack of effective mechanism enables the deep foundation pit engineering construction scheme to share and update the safety review knowledge

Related knowledge is scattered in massive various documents, technical data and expert brains, and because a huge amount of safety evaluation knowledge is difficult to master manually, and experts participating in evaluation have respective adept fields in the aspect of construction safety of deep foundation pit engineering, the experts are difficult to master all knowledge. The knowledge is accumulated in long-term engineering practice, and at present, no mature mechanism can carry out standard arrangement on the knowledge, so that the knowledge for evaluating the safety of the deep foundation pit engineering construction scheme is difficult to share, and the safety management of the deep foundation pit engineering construction is adversely affected.

In addition, in the process of continuous updating of the deep foundation pit engineering construction technology, new safety risks and new risk factors can appear, so that the safety review knowledge is continuously updated, and the difficulty of safety review knowledge sharing is increased.

(3) The information provided by the manual review result is not complete enough, has a single form and is difficult to understand and master by all people.

At present, the opinion of evaluation is often in a text form to list the events which are considered by experts to have higher risk degree, and to propose a prevention and control suggestion. Other events with lower risk levels are easily ignored; second, these events are listed individually, without reflecting the evolution path of the events and the associations between the events. In fact, complex coupling effects exist among the risk events, and obvious cause and effect relationships exist among the risk events; again, the review opinions rarely explicitly indicate when and where all risk events occur roughly, i.e., lack spatiotemporal information. The result of such a review, in fact, is that it is difficult for most of the underlying managers and front-line operators lacking comprehensive and profound engineering technical knowledge to understand, with only a few managers having sufficient technical abilities. Therefore, most of the review opinions stay at the construction management high level, and the bottom-level managers and front-line constructors most closely related to the safety risk are often not effectively guided.

A great deal of research is carried out on the theory and method aspects of the identification and evaluation of the construction safety risk of the deep foundation pit engineering at home and abroad, and the research has the following characteristics through the analysis of relevant documents:

(1) on the aspect of research subjects, the research on behavior risks is more (a large amount of research related to professional health safety review); secondly, overall evaluation of safety risks of a construction site is carried out; the research on the technical risk mostly shows that the risk size is evaluated by a certain method, and the research related to the evaluation rule is rare.

(2) In the aspect of research targets, most of the methods are the means of construction safety risk evaluation, and decision support information is provided for safety management. Some studies have integrated management goals for other aspects of project management, such as combining safety with cost management, and studying optimal safety management schemes under consideration of cost input constraints.

(3) In the aspect of research idea, most of the methods establish a set of index system on the basis of completing safety risk identification, and utilize a certain theoretical method (mostly a quantitative method) to complete risk evaluation, wherein the evaluation result is represented as the grade (aiming at a single risk) or the ranking (aiming at a plurality of risks) of the risk.

(4) The research method is divided into qualitative and quantitative categories. The qualitative analysis method is mainly used for collecting original data, such as questionnaire adjustment, expert investigation and the like, and is mainly used for establishing an evaluation index system of safety risks; the quantitative Analysis method is often expressed as a fuzzy Set (Rough Set), an Analytic Hierarchy Process (Analytic Hierarchy Process), various comprehensive evaluation theory methods, an Artificial Neural network (Artificial Neural Networks), an Event Tree (Event Tree Analysis), a Fault Tree (Fault Tree Analysis), a Support Vector Machine (Support Vector Machine), and the like, and a combination of these methods.

According to the characteristics of the research at home and abroad, the following weak links exist in the current related research.

(1) There is little research into evaluation rules relating to security technology risks.

(2) Less attention is paid to how to effectively manage the related security risk evaluation knowledge, so that the related knowledge is difficult to share.

(3) The identification and evaluation of risks lacks a systematic view, i.e. the risks are evaluated individually, taking into account less the mutual influence between the risks.

(4) The evaluation method is mostly comprehensive evaluation in theory, and is difficult to evaluate a plurality of risks with loop characteristics.

(5) There are more studies on evaluation methods, but less studies on how to manage relevant knowledge. The research on the domestic construction safety knowledge base is very weak, and at present, no knowledge base specially aiming at the construction safety technical risk of the subway deep foundation pit engineering exists, and no knowledge base capable of supporting the safety review of the subway deep foundation pit engineering construction scheme exists.

The invention also provides a patent for identifying and evaluating the safety risk in the preparation period of deep foundation pit engineering construction in the past, and is more typical 'a subway construction safety risk identification inference system and an identification inference method thereof' (ZL 201210021691.4). The patent technology discloses a method for automatically identifying and evaluating safety risks in the preparation period of subway construction, the core of the method is to establish an evaluation risk size of a comprehensive evaluation model, each calculation parameter (such as risk factor reliability) of the model needs to be set in advance, and the evaluation rule is actually a comprehensive evaluation model.

The patent technology has the following weak links:

(1) the risk factors of the safety risk have huge value combination quantity, and the action modes of the risk factors on the risk events are different. There are several decision variables for the same security risk event, some of which are related to only one risk factor and some of which are related to all risk factors. The specific situations of all safety risk events are different, the association is quite complex, only a fixed credibility is given to the risk factor value, and the aggregation function is used for calculating the evaluation value, so that the complicated relation between the risk event and the risk factor is difficult to reflect, and the engineering technical principle is not very consistent.

(2) The security risk events are evaluated individually without taking into account the coupling effects between the risk events. According to engineering principles, there is a well-defined coupling effect between safety risk events, the impact of which is bidirectional, i.e. there is a loop. If the building envelope deforms, the degree of peripheral surface subsidence is increased, and the increase of the degree of peripheral surface subsidence also increases the lateral pressure borne by the building envelope, so that the deformation of the building envelope is further increased. The engineering technology relationship is still more in deep foundation pit engineering construction, but the patent technology does not consider the coupling effect between safety risk events and is not very consistent with the engineering technology principle. The current research on the aspect of evaluating the construction safety risk of the deep foundation pit engineering also relates to the correlation less.

(3) The comprehensive evaluation model cannot handle risk systems with loop characteristics. If a risk system having a loop characteristic is established in consideration of the correlation between risk events, a common analysis method represented by an artificial neural network, the number of events, a fault tree, and the like is difficult to function in such a case.

In summary, there are many research achievements and application cases for identifying and evaluating the construction safety risk of the deep foundation pit engineering, and the research and the specific technical scheme for scientifically managing the huge amount of safety review knowledge of the deep foundation pit construction scheme have not been reported so far.

The invention fully analyzes the practical difficulty of the safety review of the construction scheme of the current deep foundation pit engineering, researches the weak links of related documents at home and abroad and the prior invention patents, fastens the technical principle of the deep foundation pit engineering, provides a safety review knowledge base of the construction scheme of the deep foundation pit engineering for scientifically managing related knowledge, stores huge amount of safety review knowledge by using the information technology, carries out structuralized treatment on the safety review knowledge, can be continuously enriched and adjusted along with the progress of the construction technology, and can enable the safety review work of the construction scheme to be based on all the review knowledge to eliminate quality risks; the dependence on experts can be reduced; the evaluation process is free from the influence of uncertain factors, the advantages of a computer on the information processing scale and speed can be exerted, and the evaluation efficiency is improved;

the automation of the deep foundation pit engineering construction scheme safety review can be realized based on the knowledge base. The coupling effect and the loop characteristic among the safety risk events are deeply researched, an evaluation model based on the system dynamics principle is established to describe the safety risk evolution process of the whole construction period, more complete review information including the evolution path and the null information which can reflect the coupling effect among the risks can be output by a computer, and the work result of the safety review can be brought to the real place.

Disclosure of Invention

The invention provides a deep foundation pit construction scheme safety review knowledge base and an automatic safety review method, overcomes the defects in the background technology, is used for managing the deep foundation pit engineering construction scheme safety review knowledge and realizes the automation of review work.

The technical scheme adopted for realizing the above purpose of the invention is as follows:

a deep foundation pit construction scheme safety review knowledge base comprises a project construction method information sub-base, a safety risk event sub-base, an adventure factor sub-base, a basic event review rule sub-base, a coupling relation sub-base and a risk grade evaluation rule sub-base;

the project construction method information sub-base is used for structuring construction method information of a construction scheme;

the safety risk event sub-library is used for storing the name and code of a safety risk event, the property of the risk event, the loss grade of the risk event and pre-control measures; the safety risk event sub-library defines each safety risk event as three event properties of a basic event, a symptom event and a loss event according to the characteristics of the risk event and the different functions of the safety risk event in the whole project safety risk system, wherein each risk event has one to two event properties;

the risk factor sub-library is used for storing risk factors related to the basic event, defining all values of the risk factors, and defining the relation between the risk factors and the basic event, wherein the relation is actually a review rule form of the basic event;

the basic event review rule sub-library is used for storing each basic event review rule;

the coupling relation sub-library is used for storing basic parameters required by coupling calculation and providing necessary calculation conditions for multi-risk evaluation calculation;

and marking corresponding risk grade labels in the risk grade evaluation rule sub-library according to different combinations of the loss event occurrence probability grade and the loss grade, and establishing a risk grade evaluation rule so as to realize the final risk grade evaluation of the loss event.

The basic event, the symptom event and the loss event are specifically as follows:

(1) basic events are as follows: in the construction process of the deep foundation pit engineering, the inducement of the basic event is directly from the construction progress, and along with the extension of the construction progress, the attribute values of the related risk factors are continuously changed, and the possibility of the basic event to generate the risk is directly changed; the basic events are divided into two types, namely basic events with the property of a symptom event and basic events with the property of a loss event;

(2) a symptom event: in the construction process of deep foundation pit engineering, the possibility of occurrence of a sign event is very high, even the sign event is inevitable, but the occurrence of the sign event does not immediately bring loss, the sign event does not bring actual loss if being effectively controlled, and subsequent events can be caused and loss can be brought if being improperly controlled;

(3) loss event: the method refers to events directly causing personnel and property loss, events which must be avoided in construction, loss events are directly or indirectly caused by symptom events or basic events, and the occurrence possibility of the events is the result of risk coupling with the events; the loss event can be a basic event by itself, the event occurrence possibility of the loss event is only influenced by risk factors associated with the loss event, and the risk flow generated by the loss event influences other events due to the nature of the basic event.

The basic event evaluation rule sub-library establishes risk occurrence probability grades of all basic events under all possible risk factor value combinations by collecting and sorting original construction information of previous construction projects, taking risk factor values of all safety risk events in actual projects as precondition, taking corresponding safety management measures in construction records as basis and taking a production expression as form;

the original construction information comprises design drawings, geological survey data, construction schemes, construction diaries, supervision diaries and meeting summary.

The basic event evaluation rules in the basic event evaluation rule sub-library adopt a production expression method, and the basic event evaluation rules consist of preconditions and decision variables, wherein the preconditions are risk factor value combinations of the basic events, the decision variables are occurrence probability levels or occurrence degree levels of the basic events, and the total evaluation rule quantity of any specific basic event is the product of all the precondition value numbers of the basic events.

The method for determining the risk accumulation rate of the basic event comprises the following steps:

(1) for a basic event with the nature of a symptom event:

firstly, selecting a plurality of finished projects with the same foundation pit design form such as an enclosure structure and a support system from the previous deep foundation pit engineering project, observing related monitoring data of the projects at each construction stage, and obtaining the evaluation level of the occurrence degree of events at each stage; then reversely calculating the average accumulation rate according to the construction time of each stage recorded by the construction diary, thereby obtaining the accumulation rate of each evaluation grade; finally, integrating data of a plurality of projects to carry out mean value processing to obtain an estimated value of the accumulation rate;

(2) basic events with loss event properties:

firstly, selecting a plurality of finished deep foundation pit engineering projects with the same foundation pit design form such as an enclosure structure and a support system, determining risk occurrence probability evaluation values of all construction stages of the projects based on expert evaluation results before the projects are started, then marking the evaluation levels of all the stages by the maximum values of corresponding evaluation value intervals, reversely calculating the average accumulation rate by taking the construction duration of all the stages as a time axis, and synthesizing the calculation results of a plurality of the projects to obtain the accumulation rate estimation value of all the risk occurrence probability levels.

The method for determining the coupling coefficient of the coupling event group comprises the following steps:

using foundation ditch bottom uplift, envelope warp and three incident of peripheral earth's surface subside as the example, there is coupling effect between the three incident, and the envelope degree of deformation can all be influenced to foundation ditch bottom uplift degree and peripheral earth's surface subside degree, and it is peripheral earth's surface subside and the accumulative monitoring value of foundation ditch bottom uplift respectively to establish A and C, and B is envelope deformation rate monitoring value, arranges 3 numbers on same time axis, then:

the coupling coefficient of the deformation of the enclosure structure and the peripheral surface subsidence is as follows:

ρ_AB＝Cov(A，B)/[Cov(A，B)+Cov(C，B)]

the coupling coefficient of the deformation of the enclosure structure and the bottom bulge of the foundation pit is as follows:

ρ_CB＝Cov(C，B)/[Cov(A，B)+Cov(C，B)]。

the invention also provides an automatic safety review method of the deep foundation pit construction scheme based on the safety knowledge base, which comprises the following steps:

(1) carrying out structuring processing on the main construction method information of the construction scheme under a frame of a project construction method information sub-library;

(2) based on the structured project construction method information, retrieving a safety risk event sub-library, extracting all safety risk events associated with the project construction method information to generate a risk identification list, wherein the safety risk event sub-library defines the reason events and the result events of each safety risk event, so that the list also comprises the reason event and the result event information of each safety risk event;

(3) searching an risk factor sub-library based on the basic events in the risk identification list, and matching corresponding risk factors for each basic event in the risk identification list;

(4) the security risk event and the result event thereof form a coupling event group, and the risk identification list comprises each security risk event and the result event information thereof, namely a plurality of coupling event groups; then, based on each coupling event group in the risk identification list, searching a coupling relation sub-library and matching corresponding coupling factors for each coupling event group;

(5) establishing an evaluation model, and assigning values to each risk factor and coupling factor based on the construction scheme information;

(6) retrieving a review rule sub-library and determining an initial evaluation value for each basic event;

(7) retrieving the sub-library of coupling relationships and determining a value of a coupling coefficient for each group of coupling events;

(8) completing the evaluation calculation of the whole construction period;

(9) and outputting an evaluation result.

The corresponding evaluation model construction principle in the step (5) is as follows:

(1) the basic event is a risk source of the whole risk system, the risk of the whole risk system at each construction stage must be evaluated according to a review rule, and risk causing factors appear in a model in the form of auxiliary variables;

(2) non-essential events, the magnitude of which is determined by coupling effects;

(3) taking Time as an axis, the value of each risk factor of all basic events in the whole construction period is a function of a shadow variable 'Time';

(4) the loss event is marked by a horizontal variable to indicate the evaluation value of the occurrence probability of the loss event, and the symptom event is also marked by a horizontal variable to indicate the evaluation value of the occurrence degree of the symptom event;

(5) the coupling effect is determined by the coupling coefficient, the magnitude of which is determined by the associated coupling factor.

Compared with the prior art, the invention has the following advantages: (1) at present, the traditional risk identification and evaluation mainly depends on the individual knowledge ability of technicians, but the ability of human brain for processing information is limited, and the human brain is difficult to completely master for the safety evaluation of huge deep foundation pit engineering construction schemes, so the evaluation quality is difficult to completely ensure; the manual evaluation work efficiency is low; at present, a knowledge base aiming at the safety evaluation of the deep foundation pit engineering construction scheme does not exist, related knowledge is not scientifically managed, and the knowledge is difficult to share and update. The invention provides a method for processing and arranging original data based on actual data generated in the previous deep foundation pit engineering construction, and establishes a large amount of safety review knowledge for managing a safety review knowledge base of a deep foundation pit engineering construction scheme so as to overcome the difficulty in the current actual work and fill up the defects of related knowledge management.

(2) The invention carries out structured arrangement on the construction scheme and construction method information, establishes a hierarchical structure of the construction method information, and associates corresponding safety risk events with each specific node in the hierarchical structure, so that a computer can carry out rapid risk identification according to the construction method information in the construction scheme to form a risk identification list. Saving a large amount of risk preliminary screening working time.

(3) The present invention defines all security risks with the concept of basic events, symptom events and loss events in a sub-library of security risk events. The three concepts describe different properties and effects of the security risk event in the whole project security risk system, and directly determine a calculation method in a flowsheet evaluation model, so that evaluation calculation is more consistent with engineering practice, and the generation and development process of the risk event is described.

(4) According to the invention, an evaluation model is not established according to a traditional method for risk evaluation, but a rule evaluation risk is directly established in an IF THEN form. The precondition value combination of the evaluation rule can express all possible actual working conditions of a specific safety risk event, the obscure theoretical calculation of a comprehensive evaluation model is avoided, and the evaluation rule is simple and clear and is closely attached to the actual work on site. Because the review rule has a simple and clear structure, the related rule can be conveniently adjusted (modified, added or deleted) in time according to the latest information, and the high sharing and timely updating of the review knowledge are ensured. The invention stores all basic event evaluation rules in a basic event evaluation rule sub-library which can theoretically store all basic event evaluation rules and collects main safety evaluation knowledge scattered in expert individuals and various literature data.

(5) The method overcomes the weakness of independent evaluation on the security risk events in the past research and practice, fully considers the coupling effect among the security risk events, establishes the relationship and the motion rule of the security risk events of the whole project described by the flow graph model, evaluates on the basis of fully considering the coupling effect, and is more in line with the mechanism of the generation and development of the security risk events, so that the evaluation result has space-time information, and provides more comprehensive and more detailed security evaluation support information.

(6) The invention provides a method for measuring the coupling effect between safety risk events according to historical monitoring data based on the analysis and the arrangement of the historical monitoring data, establishes a coupling coefficient determination formula and directly supports the evaluation and the settlement of a flow graph evaluation model.

(7) A user inputs construction method information in a deep foundation pit engineering construction scheme in sequence under the guidance of a knowledge base and an evaluation system, risk factor value information can be obtained on the basis of safety review knowledge of all deep foundation pit construction schemes, safety review of the deep foundation pit engineering construction scheme is carried out, the safety review result of the deep foundation pit engineering construction scheme is obtained quickly by utilizing the advantages of a computer in information processing efficiency and quality, the result has more comprehensive and more detailed safety review support information which is difficult to complete in a short time through manual review, the user can conveniently and specifically master safety management in a construction stage according to the review result, and automation and scientization of safety risk management are achieved.

Drawings

FIG. 1 is a logical structure diagram of a deep foundation pit construction scheme safety review knowledge base provided by the present invention;

FIG. 2 is a block diagram of a deep foundation pit construction scheme safety review knowledge base provided by the present invention;

FIG. 3 is a structural diagram of a deep foundation pit construction scheme safety review knowledge base provided by the invention;

FIG. 4 is a diagram illustrating the coupling between security risk events in an embodiment of the present invention;

FIG. 5 is a flowchart of a deep foundation pit construction scheme safety review method provided by the invention;

fig. 6 is a frame diagram of the deep foundation pit construction scheme safety review system provided by the invention.

Detailed Description

The present invention will be described in detail with reference to specific examples, but the scope of the present invention is not limited to the examples.

The logical structure diagram of the deep foundation pit construction scheme safety review knowledge base provided by the invention is shown in fig. 1, the module diagram is shown in fig. 2, and the structure diagram is shown in fig. 3. The system comprises a project construction method information sub-base, a safety risk event sub-base, an risk factor sub-base, a basic event evaluation rule sub-base, a coupling relation sub-base and a risk grade evaluation rule sub-base.

And the project construction method information sub-base is used for structuring construction method information of the construction scheme.

And the safety risk event sub-library is used for storing the name and the code of the risk event, the property of the risk event, the loss grade of the risk event and the pre-control measure. And the safety risk event sub-library structurally stores the key information required by the safety evaluation by taking the risk event as an object to become a core sub-library of the knowledge base.

And the risk factor sub-library is used for storing risk factors related to the basic event, defining all possible values of the risk factors, and defining the relation between the risk factors and the basic event, wherein the relation is actually a review rule form of the basic event. And the risk factor sub-library structurally stores the risk factors related to the basic events to become a basic sub-library of the knowledge base.

And the basic event review rule sub-library is used for storing each basic event review rule. The review rule form may be literally expressed as "if … … risk factor value combinations exist, then the risk occurrence probability rating is … …". After determining risk factors and values of any basic event, the rules which accord with corresponding risk factor value combinations can be searched in the basic event review rule sub-library, risk occurrence probability grades are marked for the basic events, and original data are established for risk evaluation from the whole project level.

And the coupling relation sub-library is used for storing basic parameters required by the coupling calculation and providing necessary calculation conditions for the multi-risk evaluation calculation. Once the event group with the coupling relation is provided for the coupling relation sub-library, the coupling relation sub-library can establish a corresponding coupling factor for the event group; then, assigning values to the coupling factors according to the construction scheme information; and finally, according to the coupling factors after assignment, finding corresponding coupling coefficients in the coupling relation sub-library, and completing the coupling relation definition of the multi-risk evaluation model.

The risk grade evaluation rule sub-library is used for establishing a risk grade judgment rule according to a determination standard for risk grade in urban rail transit underground engineering construction risk management regulations (GB 50652-2011). According to different combinations of the loss event occurrence probability grade and the loss grade, corresponding risk grade class labels are marked, so that risk grade evaluation rules can be established, and the rules are uniformly stored in a risk grade evaluation rule sub-library to realize the final risk grade evaluation of the loss event.

The risk factor sub-library standardizes the value of the risk factors, and makes the technical information in the construction scheme structured so as to meet the requirements of an evaluation model and perform evaluation calculation; the safety risk event sub-library defines reason events and result events of safety risk events, and makes up the defects of the conventional safety risk evaluation, so that the evaluation model considers the coupling effect between the safety risk events and is more in line with the engineering practice; the safety risk event sub-library defines three event properties of a basic event, a symptom event and a loss event for each safety risk event according to the characteristics of the safety risk event and the different functions of the safety risk event in the whole project safety risk system, each safety risk event has one to two event properties, and the different event properties have different processing methods in an evaluation model, so that the evaluation calculation can more accurately describe the characteristics of the safety risk event and the functions of the safety risk event in the whole project safety risk system and better accord with the engineering practice; the basic event review rule sub-library is formed by collecting and organizing original construction information (including design drawings, geological survey data, construction schemes, construction diaries, supervision diaries, meeting summary and the like) of previous construction projects, taking risk factor values of all safety risk events in actual projects as precondition, taking corresponding safety management measures in construction records as basis and taking a production expression as form, and establishing risk occurrence probability grades of all basic events under all possible risk factor value combinations to enable basic events of projects to be evaluated to rapidly determine initial evaluation values.

The concepts of the basic event, the symptom event and the loss event are as follows:

(1) a basic event. In the construction process of deep foundation pit engineering, the inducement of some risk events is directly from the construction progress. The attribute value of the risk factor related to the event is continuously changed along with the extension of the construction progress, and the change directly causes the risk occurrence possibility of the event to be changed. Such as: along with the continuous increase of excavation depth of foundation ditch, lead to foundation ditch bottom uplift degree to constantly increase. The direct result of the increase of the uplift degree of the foundation pit bottom is that the deformation degree of the enclosure structure and the peripheral ground surface settlement degree are increased, wherein the uplift of the foundation pit bottom is a basic event. The basic event has two typical characteristics, namely, the risk of the event is directly influenced by the construction progress; and secondly, the generated risk amount is the source of the risk flow, and is the source of the risk flow in the whole deep foundation pit engineering construction safety risk system, in other words, the risk of non-basic events is directly or indirectly brought by the basic events. An event of this nature may therefore be referred to as a base event.

(2) And (4) a symptom event. In the construction process of deep foundation pit engineering, some events have high possibility and even inevitably occur, but the occurrence of the events does not bring loss immediately. These events, if effectively controlled, do not result in an actual loss, and if improperly controlled, may result in subsequent events and a loss. The events need to be faced and treated for a long time in the construction process of the deep foundation pit engineering, and an experienced construction unit can decide whether to take measures for control according to the occurrence degree of each event. Such as the bottom of the foundation pit uplifting, the deformation of the building envelope, the subsidence of the surrounding earth surface and the like. Along with the extension of the construction progress, the excavation depth of the foundation pit is continuously increased, risk factors such as the soil penetration ratio of the enclosure structure, underground water and the like are continuously changed disadvantageously, and the bottom uplift degree of the foundation pit, the deformation degree of the enclosure structure and the settlement degree of the peripheral earth surface are increased. However, these events do not directly bring about the loss, and as long as the degree is within a controllable range, the probability of bringing about the occurrence of the subsequent events is considered to be small. If the deformation of the enclosure structure is influenced by the bottom bulge of the foundation pit, the larger the bottom bulge degree of the foundation pit is, the larger the deformation degree of the foundation pit is. The risk flow generated by the bottom bulge of the foundation pit flows to the deformation event of the enclosure structure, and is coupled in the risk transmission process, so that the deformation degree of the enclosure structure is changed. If the deformation degree of the building envelope is not well controlled, the building envelope is allowed to develop, and finally the water and sand gushing of the building envelope or the collapse event of the building envelope can be caused, and the loss is caused. Therefore, the events which are likely to even certainly occur in the construction process of the deep foundation pit engineering and can cause loss without direct loss can be called symptom events.

(3) A loss event. Loss events refer to events that directly bring about loss of personnel and property and must be avoided during construction. Such as water and sand gushing at the bottom of the foundation pit, collapse of the building enclosure, water and sand gushing of the building enclosure, damage of peripheral pipelines or buildings and the like. Loss events are caused directly or indirectly by either a symptom event or a base event, the event occurrence probability of which is a result of risk coupling with these events. The loss event may be a basic event itself, and the event occurrence probability is only influenced by risk factors associated with the loss event itself, and the loss event has the property of a basic event, so that the generated risk flow influences other events.

The relationship between events is complex and intricate, and some events have two properties at the same time.

Each rule in the basic event review rule sub-library adopts a production expression method, and the rule consists of a precondition and a decision variable, wherein the precondition is the value combination of risk factors of the basic event, and the decision variable is the 'occurrence probability grade' (aiming at loss events) or 'occurrence degree grade' (aiming at symptom events) of the basic event. The total review rule number for a particular base event is the product of all preconditions (risk factors) for that base event. For example, for a basic event of "water and sand gushing at the bottom of a foundation pit", the evaluation rule can be collectively represented in table 1, the event has six risk factors, the possible value number of each risk factor is 4, 3, 2, and 2, then there are 432 evaluation rules for the basic event, and these 432 rules cover all possible conditions (all value combinations of risk factors) of the basic event in reality, and all evaluation knowledge of the basic event is expressed.

TABLE 1 Risk occurrence probability ranking criteria

The method for determining the decision variables of the rules in the basic event review rule sub-library and the evaluation value intervals corresponding to the decision variables comprises the following steps:

basic events are divided into two categories, namely basic events with the nature of a sign event and basic events with the nature of a loss event. For basic events with loss event properties, the evaluation rule is in the form of: "if there is … … risk factor value combination, the risk occurrence probability level is … …", the risk factor value combination is a condition variable, and the risk occurrence probability level is a decision variable.

Referring to the regulations of each early warning level management measure of the safety risk events in the subway engineering construction safety review standard (GB50715-2011), corresponding to five safety risk event occurrence probability levels in the urban rail transit underground engineering construction risk management standard (GB50652-2011), management measure features corresponding to basic event occurrence probability levels having loss event properties can be defined, as shown in table 1.

According to the evaluation terms in table 1, the risk event occurrence probability level under each risk factor value combination at that time can be determined according to the management measures at that time aiming at various actual occurrence conditions accumulated in the past construction.

For a basic event with the property of a symptom event, the evaluation rule is in the form of: if … … risk factor value combinations exist, the occurrence degree of an event is … … ", the risk factor value combination is a condition variable, and the occurrence degree of the event is a decision variable. The indication of the degree of occurrence is understood to mean that the risk pressure caused by the degree of occurrence of the symptom event, for example, the risk pressure caused by the deformation of the building envelope reaching the alarm value, is greater than the pressure caused by the deformation of the building envelope only 20% of the alarm value. Because the symptom event and the loss event are marked by a dimensionless evaluation value to indicate the occurrence degree and the occurrence possibility of the event, a uniform evaluation standard should be formulated to ensure the evaluation accuracy.

The implications of the evaluation values of the symptom event and the loss event are different due to the difference of the nature of the event, so the evaluation values of the symptom event and the loss event are unified and standard, and the evaluation can be carried out in one model.

According to the safety early warning management principle of a construction site, when a symptom event reaches a warning value, an emergency plan is started on the site, control countermeasures are researched, such countermeasures are consistent with those taken by the fact that the risk occurrence probability grade in table 1 is 'frequent', and the practical meaning is that the site takes the symptom event at the moment as a loss event with the highest occurrence probability grade, so that the highest evaluation value grade of the symptom event is defined as 'unsafe', the standard is 'reaching and exceeding a monitoring warning value', and the evaluation value interval corresponds to the 'frequent' occurrence probability grade of the loss event. And according to the safety early warning management principle, when the monitoring data reaches an alarm value of 80%, a field early warning mechanism is triggered, the monitoring frequency of the early warning position is strengthened and the important attention is paid to the early warning position on the field, and the management measures are consistent with the counter measures which are taken according to the risk occurrence probability grade in the table 1. This degree of symptom event is therefore defined as "basic safety" whose criterion is to reach 80% but not exceed 100% of the warning value. When the site warning mechanism is not triggered, it may be defined as "safe".

According to the classification standard of the risk occurrence probability grades in the urban rail transit underground engineering construction risk management regulations (GB50652-2011), the probability intervals of all adjacent grades are different by an order of magnitude. Therefore, when evaluating the risk occurrence probability level of a risk event, a dimensionless number can be used to indicate the occurrence degree (for symptom event) or the occurrence probability (for loss event) of the risk event. But the number of adjacent levels is kept an order of magnitude apart. The basic definitions are shown in table 2.

TABLE 2 symptom event occurrence degree and loss event occurrence probability definition Table

(1) basic events with symptom event properties

The symptom event cannot evaluate the occurrence probability, and can only evaluate the occurrence degree.

Firstly, a plurality of finished projects with the same foundation pit design form (a building enclosure and a support system) are selected from the conventional deep foundation pit engineering projects. Observing related monitoring data of the construction system at each stage to obtain the evaluation grade of the occurrence degree of the event at each stage, wherein the method for determining the occurrence degree of the event is according to the table 2; then reversely calculating the average accumulation rate according to the construction time of each stage recorded by the construction diary, thereby obtaining the accumulation rate of each evaluation grade; and finally, integrating the data of a plurality of projects to carry out mean value processing to obtain an estimated value of the accumulation rate.

(2) Base events with loss event properties

Loss events assess their likelihood of occurrence.

First, a plurality of completed deep foundation pit engineering projects in the same foundation pit design form (envelope and support system) may be selected. And determining the risk occurrence probability evaluation value of each construction stage of the project based on the expert review result before the start of each project. Then, the evaluation level of each stage is labeled with the maximum value of the corresponding evaluation value section (defined in table 2), and the average accumulation rate is reversely estimated with the construction duration of each stage as the time axis. And integrating the estimation results of the plurality of items to obtain the accumulation rate estimation value of each risk occurrence possibility level.

A flowchart of the deep foundation pit construction scheme safety review method provided by the embodiment is shown in fig. 5. The frame diagram of the deep foundation pit construction scheme safety review system provided by the embodiment is shown in fig. 6. In this embodiment, the invention is further described by taking a review process of a specific project as an example, and the main information of the deep foundation pit engineering construction scheme of the project is as follows:

(1) the project has two layers of basements, the deep foundation pit project is rectangular, the total external packing length is 158.6m, the total external packing width of the standard section is 20.9m, and the total building area of the foundation basements is 14073m 2. The ground elevation of the foundation pit is 22-24 meters, and the maximum excavation depth of the foundation pit is 19.1 meters.

(2) The properties of the stratum at the position of the foundation pit are as follows from top to bottom: miscellaneous filling, silty clay, fine sand and stroke fossil rock, wherein the stratum to which the foundation pit bottom belongs is the fine sand; the underground water in the range of the foundation pit is upper-layer stagnant water and confined water, wherein the upper-layer stagnant water exists in a miscellaneous fill layer and is supplied by surface water, the confined water exists in a fine sand layer, the upper-layer powdery clay is a water-proof top plate of the fine sand layer, and the confined water head is 4 meters below a natural terrace of the foundation pit.

(3) The foundation pit is constructed by an open cut method; the enclosure structure is an underground continuous wall, the stratum at the bottom of the wall is a silty sand layer, and the maximum soil penetration ratio is 0.7; four steel supports are adopted; a large number of underground pipelines are arranged around the underground pipeline, including a water supply pipe, a sewage pipe, power, communication and the like; and existing buildings are arranged at the periphery of the foundation pit.

(4) According to the construction scheme, the construction schedule of the standard construction section of the foundation pit is shown in table 3.

Aiming at the above situation of the project, the adopted safety evaluation method is as follows:

(1) establishing a project to be evaluated

Firstly, a new project is established in the system, and a project name, a construction unit, an exploration unit, a design unit, a construction unit, a supervision unit, a project general view and the like are established.

(2) Information of construction method

And establishing the main construction method information of the deep foundation pit engineering in the review system according to the information provided by the construction scheme of the deep foundation pit engineering. In the review system, the construction method information is established on the basis of the construction method hierarchical structure, the construction method hierarchical structure is provided for a user in a form of selection questions, and the user can establish the construction method information only by simply selecting the construction method hierarchical structure.

(3) Rapid risk identification

And the evaluation system retrieves the sub-library of the safety risk events according to the construction method information of the deep foundation pit engineering and automatically screens out all safety technical risks of the deep foundation pit engineering.

(4) Matching risk factors for basic events

And the evaluation system searches the risk factor sub-library according to the basic events in the identified risk events and matches corresponding risk factors for all the basic events.

(5) Matching coupling factors for coupling events

The evaluation system searches the coupling relation sub-library according to the identified risk events, establishes coupling event groups for each event matching with the corresponding result event, and matches all the coupling event groups with the corresponding coupling factors.

(6) Generating a risk identification manifest

The information of (3), (4) and (5) is integrated into the risk identification list.

(7) Establishing risk factor and coupling factor value information

Entering a vensim module, establishing a value function of each risk factor and coupling factor in the whole construction period according to the deep foundation pit engineering construction plan, and defining values of all risk factors and coupling factors. Taking an adventure factor "foundation pit soil quality" as an example, the adventure factor is defined in a table function manner, wherein a first column of data "input" is working days, the construction section plans to be completed in 70 working days, the definition of each construction stage is shown in table 3, and a second column of data "output" is a soil quality code.

(8) Establishing an evaluation model

And establishing a deep foundation pit engineering multi-risk rating model for evaluation and calculation. When risk evaluation calculation is carried out, the evaluation system is externally hung with a vensim system analysis module, and a multi-risk evaluation model is established according to the mutual relation information of all risk events in the risk identification list and risk factor information of the basic events to complete evaluation calculation.

The evaluation model of the multi-construction section is too complex and has huge data volume, and the evaluation model of the multi-construction section is formed by combining a plurality of evaluation models of single construction sections. For clarity and conciseness, the calculation process and result of the background of the evaluation system are analyzed and reviewed by taking a standard construction section of the deep foundation pit project as an example.

The deep foundation pit engineering is a typical open cut method deep foundation pit engineering, the engineering has 11 safety risk events, and according to project initial information defined in the system, the review system determines the 11 safety risk events, the coupling relation among the safety risk events and risk factors of basic events. The coupling relationship between 11 security risk events is shown in fig. 4, and 11 security risk events constitute a multi-risk evaluation model.

(1) The whole model has 11 events, 5 of which are basic events. Because the evaluation rules of two basic events of foundation pit bottom heave and foundation pit bottom water inrush sand are complex, for the sake of clarity and conciseness, the auxiliary variable expressing the part of the calculation process is deleted, and the shadow variable Time is directly used for inputting the evaluation value in the form of a table function.

(2) And establishing an equation. The number of equations in the model is very large, and the following equation is listed by taking the water inrush and sand inrush event of the building envelope as an example:

① Risk of gushing water and sand of building enclosure RATE ═

IF THEN ELSE (Time ═ 50, IF THEN ELSE (foundation pit range groundwater ═ 0,0, IF THEN ELSE (foundation pit range groundwater ═ 1,0.025, IF THEN ELSE (foundation pit range groundwater ═ 2: AND: enclosure type ═ 0: AND: longitudinal waterproof curtain ═ 0,0.05, IF THEN ELSE (foundation pit range groundwater ═ 2: AND: enclosure type ═ 1: AND: longitudinal waterproof curtain ═ 1,0.1,0.075)))) 0).

② evaluation value of sand gushing risk of water gushing of building envelope is INTEG (evaluation value of sand gushing risk of water gushing of building envelope accumulation speed, 0)

③ building envelope water and sand gushing risk occurrence probability evaluation value accumulation speed is building envelope water and sand gushing risk occurrence probability evaluation value is building envelope water and sand gushing risk RATE + risk coupling speed 10+ risk coupling speed 11

(3) The rate variable of the causal event is pointed to between the events with causal relationship by the level variable of the causal event, the risk coupling quantity of the causal event to the causal event is expressed, the coupling quantity is influenced by different coupling coefficients, and the coupling coefficients depend on the conditions of the related coupling factors. Two typical examples are described below.

① coupling coefficient 1. the coupling coefficient 1 affects the coupling quantity of the deformation risk quantity of the enclosure structure to the bottom heave of the foundation pit, and the value is affected by two coupling factors, namely the enclosure structure type and the enclosure structure rock entering condition.

IF THEN ELSE (envelope in-rock condition is 0: AND: envelope type is 0,0.025, IF THENELSE (envelope in-rock condition is 1: AND: envelope type is 1,0.1,0.05))

In the formula, the rock entering condition of the enclosure structure is equal to 0, and the rock entering condition of the enclosure structure is equal to 1, and the enclosure structure does not enter the rock; the envelope type is 0 to represent that the envelope is an underground continuous wall, and the envelope type is 1 to represent that the envelope is a row pile.

The rule expressed by the formula is: the coupling coefficient is 0.025 under the condition that the enclosure structure enters rock and is an underground continuous wall; under the condition that the building envelope is not in rock and is in a row pile; the coupling coefficient was 0.1, and in other cases 0.05.

The risk coupling speed 1 represents the risk coupling quantity of the deformation of the enclosure structure to the bottom uplift of the foundation pit, and is a function of a shadow variable Time, the deformation risk quantity of the enclosure structure and a coupling coefficient 1, and the equation is as follows:

IF THEN ELSE (Time 40, envelope deformation risk factor 1,0)

The rule expressed by the formula is: if the time is less than or equal to 40 days, the risk coupling speed 1 is equal to the product of the deformation risk amount of the enclosure and the coupling coefficient 1; in other periods, the risky coupling speed 1 is 0. The engineering meaning is that according to the construction schedule, after 40 working days, the foundation pit is sealed, the occurrence degree of the sign event of the foundation pit bottom uplift is regarded as stop, so that the risk is not input any more, the coupling degree of the foundation pit bottom uplift and the enclosure structure deformation is 0, and the foundation pit bottom uplift and the enclosure structure deformation are mutually independent.

② coupling coefficient 6. coupling coefficient 6 affects several risk coupling speeds simultaneously, in risk coupling speed 11, it affects the coupling quantity of water pipe leakage risk to the gushing water and sand of the enclosure structure.

IF THEN ELSE (envelope type 0,0.025,0.075)

In the formula, the envelope type is 0, which means that the envelope is an underground continuous wall. The engineering meaning expressed by the formula is that if the building envelope is an underground continuous wall, the risk coupling coefficient is smaller, and if the building envelope is a row pile, the risk coupling coefficient is larger. The underground continuous wall has strong system rigidity and waterproof performance, and is one of the most powerful water retaining capacities in the common enclosure structure.

(4) And (4) evaluating and calculating.

①, finishing an evaluation at the beginning of the first stage, and taking the lowest value of the grade evaluation value interval as the initial value of each level variable according to the evaluation result, if the evaluation result at the beginning of the first stage of the foundation pit bottom ponding bubble tank is impossible, setting the initial value of the level variable of the foundation pit bottom ponding bubble tank to 0, if the evaluation result is occasional, setting the initial value to 100.

② starting evaluation calculation for ten consecutive days, each event level variable will accumulate and express the accumulation effect of each event in the evaluation process.

③, finishing the second evaluation at the beginning of the second stage, comparing the evaluation value with the last value of the previous stage for the event that the first risk factor (risk factor providing risk energy) has continuous influence on the current stage, and taking the large value as the initial value of the current stage, and taking the minimum value of the evaluation value interval to which the evaluation level of the current stage belongs as the initial value of the current stage for the event that the first risk factor of the previous stage has no continuous influence on the current stage.

For example, in a foundation pit bottom water accumulation bubble groove event, the underground water condition is a first risk causing factor, and once the underground water condition changes along with the increase of the excavation depth, the influence of the property of the upper-layer underground water on the event disappears; however, other events belong to the former, such as water burst and sand gushing events of the enclosure structure, and no matter where the excavation depth of the foundation pit is, the upper-layer groundwater has continuous influence on the events.

④ the method is followed to complete each stage evaluation.

(5) Analysis of model calculation results

① little risk evaluation value is generated at the first construction stage due to shallow water retention and poor soil quality (filling with impurities), no underground water and cohesive soil are generated at the 2 nd and 3 rd stages, the risk evaluation value is 0 at the 4 th stage due to confined water and large difference between the internal and external water heads of the foundation pit, and sandy soil is sensitive to underground water, and the risk evaluation value is restored to 0 at the 5 th, 6 th and 7 th stages due to the foundation pit being sealed.

② the risk of instability of the steel support always follows the same direction change of the deformation degree of the building envelope, the risk amount is increased from the first stage of construction until the seventh stage, and the risk occurrence probability evaluation value is 0 because all the steel supports are dismantled.

③ the evaluation value of the deformation degree of the enclosure structure is coupled by the risks of the events of water gushing and sand gushing at the bottom of the foundation pit, the bottom of the foundation pit uplifting, the instability of steel supports and the settlement of the peripheral earth surface, the events are gradually accumulated from 0 to the seventh construction stage in the first construction stage, and the evaluation value of the event is stable and still because the evaluation values of the events are all 0 for several reasons for providing risk flow for the events.

④ the water and sand gushing of the enclosure is not only a loss event but also a basic event, and is influenced by underground water, meanwhile, the increase of the deformation degree of the enclosure can reduce the sealing performance of the enclosure, weaken the risk inhibition capability of the second risk factor (coupling factor), and the increase of the peripheral water pipe leakage risk evaluation value can also increase the influence of the first risk factor on the water and sand gushing risk event of the enclosure.

⑤ the settlement degree of the surrounding earth surface is a sign event, and is influenced by the ground surface settlement event caused by the uplift of the foundation pit bottom, the deformation of the building enclosure, the gushing of water and sand of the building enclosure and the precipitation.

⑥ the leakage of the peripheral water pipe is directly affected by the settlement of the peripheral earth surface, which is the first risk factor, and the material, pressure type and distance from the foundation pit of the water pipe are the second risk factors (coupling factors), which determine the magnitude of the risk coupling amount.

⑦ the uplift of the foundation pit bottom is a basic event and a sign event, the evaluation value of the event increases along with the increase of the excavation depth of the foundation pit and is influenced by the surrounding ground subsidence and the deformation of the building envelope, and the evaluation value of the event is 0 in the subsequent construction stage along with the bottom sealing of the foundation pit at the end of the fourth construction stage.

⑧ precipitation induced peripheral surface subsidence is a fundamental event that is separated from the peripheral surface subsidence events as a fundamental event since the peripheral surface subsidence induced by precipitation is directly related to the progress of the construction, the direct cause of the event is the increase in the voids between the earth caused by artificially lowering the water table, causing the particles of the earth to rearrange under the influence of gravity.

⑨ surrounding building damage and enclosure collapse are the top level loss events of the overall risk system, the resulting losses are all catastrophic the only causes of the two events are surrounding ground subsidence and enclosure deformation.

IF THEN ELSE (Time < ═ 50, envelope deformation degree evaluation value, IF THEN ELSE (Time >60,0,10))

The engineering implication of the formula is that before the negative second floor of the deep foundation pit engineering main structure is finished, the risk is influenced by the deformation degree of the enclosure structure, when the negative second floor is finished, the soil penetration ratio of the foundation pit enclosure structure is greatly increased, and the part of the enclosure structure below the negative second floor can be assumed to be infinite in rigidity due to the completion of the negative second floor, the collapse resistance is greatly improved, and the risk occurrence possibility evaluation value is directly judged to be rare; when minus one floor is finished, the risk of the building envelope collapse can be judged as impossible.

Of the above 11 safety risk events, there are 6 loss events whose evaluation values change at each stage of construction.

⑩ after the evaluation of any horizontal variable, according to the total risk of the variable flowing into the source, at any time, the risk of each source is examined (the rate variable flowing into the horizontal variable is examined), the main cause event and the secondary cause event causing the value of the horizontal variable at the time can be judged.

⑾, the probability level of each loss event is determined, and the equation in the vensim module is:

IF THEN ELSE (each risk occurrence probability evaluation value <10,0, IF THEN ELSE (each risk occurrence probability evaluation value > 10: AND: each risk occurrence probability evaluation value <100,10, IF THEN ELSE (each risk occurrence probability evaluation value > 100: AND: each risk occurrence probability evaluation value <1000,20, IF THEN ELSE (each risk occurrence probability evaluation value > 1000: AND: each risk occurrence probability evaluation value <10000,30,40))), wherein 0,10,20,30,40 represent 5 levels of impossible, rare, occasional, possible, AND frequent, respectively.

(6) And (5) evaluating the risk level. To complete the evaluation of the risk level requires completion of the risk occurrence probability level evaluation and the risk loss level evaluation. The loss grade evaluation of the risk events is mainly carried out from the perspective of personnel and economic loss, the urban rail transit underground engineering construction risk management standard makes detailed regulations on the evaluation method and the evaluation standard of the loss grade, and the 6 loss events are subjected to multi-turn discussion and evaluation by an organization expert to respectively determine the loss grade of the 6 loss events. And (4) completing the risk grade evaluation of each loss event by using the determination standard about the risk grade in the urban rail transit underground engineering construction risk management standard.

Claims

1. A deep foundation pit construction scheme automatic safety evaluation method based on a safety knowledge base is characterized by comprising the following steps: the knowledge base comprises a project construction method information sub-base, a safety risk event sub-base, an risk factor sub-base, a basic event evaluation rule sub-base, a coupling relation sub-base and a risk grade evaluation rule sub-base; the project construction method information sub-base is used for structuring construction method information of a construction scheme; the safety risk event sub-library is used for storing the name and code of a safety risk event, the property of the risk event, the loss grade of the risk event and pre-control measures; the safety risk event sub-library defines each safety risk event as three event properties of a basic event, a symptom event and a loss event according to the characteristics of the risk event and the different functions of the safety risk event in the whole project safety risk system, wherein each risk event has one to two event properties; the risk factor sub-library is used for storing risk factors related to the basic event, defining all values of the risk factors, and defining the relation between the risk factors and the basic event, wherein the relation is actually a review rule form of the basic event; the basic event review rule sub-library is used for storing each basic event review rule; the coupling relation sub-library is used for storing basic parameters required by coupling calculation and providing necessary calculation conditions for multi-risk evaluation calculation; marking corresponding risk grade labels in the risk grade evaluation rule sub-library according to different combinations of the loss event occurrence probability grade and the loss grade, and establishing a risk grade evaluation rule to realize the final risk grade evaluation of the loss event;

the automatic safety evaluation method comprises the following steps:

(8) completing the evaluation calculation of the whole construction period;

(9) outputting an evaluation result;

in the above step, the method for determining the coupling coefficient of the coupling event group includes:

three events of foundation pit bottom uplift, building enclosure deformation and peripheral earth surface settlement exist, coupling effect exists among the three events, the deformation degree of the building enclosure can be influenced by the uplift degree of the foundation pit bottom and the peripheral earth surface settlement degree, A and C are respectively set as the accumulated monitoring values of the peripheral earth surface settlement and the foundation pit bottom uplift, B is a building enclosure deformation rate monitoring value, 3 numbers are arranged on the same time axis, and then

The coupling coefficient of the deformation of the enclosure structure and the peripheral surface subsidence is as follows: rho_AB＝Cov(A，B)/[Cov(A，B)+Cov(C，B)]

The coupling coefficient of the deformation of the enclosure structure and the bottom bulge of the foundation pit is as follows: rho_CB＝Cov(C，B)/[Cov(A，B)+Cov(C，B)]。

2. The automatic safety evaluation method for the deep foundation pit construction scheme according to claim 1, characterized in that: the corresponding evaluation model construction principle in the step (5) is as follows: