Disaster prevention life circle spatial form optimization method based on refuge accessibility

Abstract

The invention discloses a disaster prevention life circle spatial form optimization method based on refuge accessibility. The disaster prevention life circle spatial form optimization method comprises the following steps: S1, establishing a disaster prevention life circle; s2, according to a crowd evacuation process from an evacuation starting point to an evacuation road and finally to a refuge space, calculating morphological parameters of refuge reachability of the disaster prevention life circle, and performing quantitative processing; s3, the disaster prevention life circles are divided into multiple classes, and the disaster prevention life circles meeting the preset requirements are selected as evacuation analogue simulation samples; s4, setting crowd parameters, constructing a disaster prevention life circle evacuation simulation model according to the evacuation simulation sample, and performing crowd evacuation simulation; s5, based on a crowd evacuation simulation result, calculating a refuge reachability evaluation index; s6, the correlation degree between the morphological parameters and the refuge reachability evaluation indexes is calculated, and the morphological parameters generating positive correlation and negative correlation on the refuge reachability are extracted as key morphological elements; and S7, optimizing the space form of the disaster prevention life circle based on the associated features of the key form elements and the refuge accessibility.

Description

Technical Field

[0001] The present invention relates to the field of urban disaster prevention and refuge, and more particularly, to a method for optimizing the spatial form of a disaster prevention living circle based on refuge accessibility. Background Art

[0002] With the increasing density of urban population and the complexity of functional structure, the vulnerability of cities in the face of sudden disasters has gradually emerged. The living circle planning method starting from the characteristics of residents' walking activities not only reshapes the urban safety pattern, but also gives rise to a new disaster prevention concept - the disaster prevention living circle. Due to the limitations of the built environment, the refuge accessibility of the disaster prevention living circle may not reach the ideal state.

[0003] Currently, the research on the disaster prevention living circle focuses on two levels. One is the research on the macro level such as the division method and hierarchical system; the other is the research on the micro level such as refuge places and facility configuration. However, the research on the form and existing typical forms at the meso level is relatively lacking. In addition, when analyzing the refuge accessibility, the existing research only focuses on the description and evaluation of the results, ignoring the statistical analysis of influencing factors. This makes it difficult for researchers to determine the key factors affecting the refuge accessibility and their specific influencing degrees, and thus causes decision-making blind spots for the government and designers during planning.

[0004] In fact, the form of the disaster prevention living circle, such as plot ratio and road density, plays a crucial role in the refuge accessibility. A reasonable form design can significantly improve the refuge ability of residents during disasters. Therefore, there is an urgent need for a new method to reveal the internal mechanism between the form of the disaster prevention living circle and the refuge accessibility through quantitative analysis to support scientific disaster prevention living circle optimization strategies. Summary of the Invention

[0005] The present invention provides a method for optimizing the spatial form of a disaster prevention living circle based on refuge accessibility to solve the technical problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides a method for optimizing the spatial form of a disaster prevention living circle based on refuge accessibility, which includes:

[0007] S1: Extract the quantity and location information of the residential-level refuge spaces in the target city, extract the refuge space samples, obtain the geographical area range where the refuge space samples are located from the map, and establish a disaster prevention living circle;

[0008] S2: Calculate the morphological parameters of the refuge accessibility of the disaster prevention living circle according to the crowd evacuation process from the evacuation starting point to the evacuation road and finally to the refuge space, and perform quantitative processing. The morphological parameters include the evacuation starting point morphological parameters, the evacuation road morphological parameters, and the refuge space morphological parameters;

[0009] S3: According to the typical characteristics of the disaster prevention living circle, divide the disaster prevention living circle into multiple categories, and select the disaster prevention living circles with each morphological parameter between 20% and 80% in each category of disaster prevention living circles as the evacuation simulation samples;

[0010] S4: Set the crowd parameters and construct an evacuation simulation model of the disaster prevention living circle based on the evacuation simulation samples, and conduct crowd evacuation simulation. Setting the crowd parameters includes setting the following items (1) to (4):

[0011] (1) Set the number of people and population density in the neighborhood,

[0012] (2) Set the initial position, end position, and evacuation behavior rules of the crowd,

[0013] (3) Set the gender composition and age composition of the evacuees,

[0014] (4) Set the body data, initial speed, and walking speed of people of different genders and ages;

[0015] S5: Based on the crowd evacuation simulation results, calculate the evacuation accessibility evaluation indicators. The evacuation accessibility evaluation indicators include the ten-minute evacuation success rate, total evacuation time, congestion mileage ratio, and congestion time;

[0016] S6: Calculate the correlation degree between the morphological parameters and the evacuation accessibility evaluation indicators, and extract the morphological parameters that have a positive or negative correlation with the evacuation accessibility as the key morphological elements;

[0017] S7: Optimize the spatial form of the disaster prevention living circle based on the correlation characteristics between the key morphological elements and the evacuation accessibility.

[0018] In an embodiment of the present invention, in step S1, the evacuation space samples are extracted by using the random sampling survey method, and the types of evacuation spaces include schools and parks.

[0019] In an embodiment of the present invention, in step S2,

[0020] The morphological parameters of the evacuation starting point include the floor area ratio, building density, and neighborhood entrance and exit density,

[0021] The morphological parameters of the evacuation road include road density, road network connectivity, intersection density, T-junction rate, and average road width,

[0022] The morphological parameters of the evacuation space include the evacuation space patch index and the evacuation space shape index,

[0023] The floor area ratio (FAR) refers to the ratio of the total above-ground building area in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0024]

[0025] Among them, S i is the total floor area of the i-th building, A s is the total area of the disaster prevention living circle, and n is the total number of buildings.

[0026] The building density BD refers to the ratio of the total base area of all buildings in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0027]

[0028] Among them, f i is the floor area of the i-th building.

[0029] The neighborhood entrance density DNE refers to the ratio of the number of neighborhood entrances in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0030]

[0031] Among them, N n is the number of neighborhood entrances.

[0032] The road density RD refers to the ratio of the total length of all roads in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0033]

[0034] Among them, R L is the total length of all roads in the disaster prevention living circle.

[0035] The road network connectivity RC refers to the ratio of the number of connection paths of all nodes in the disaster prevention living circle to the total number of nodes. The calculation formula is as follows:

[0036]

[0037] Among them, k i is the number of paths connected to the i-th node, and N I is the total number of nodes.

[0038] The intersection density DI refers to the ratio of the total number of nodes in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0039]

[0040] The T-shaped intersection rate TR refers to the ratio of the number of T-shaped road intersection nodes to the total number of nodes. The calculation formula is as follows:

[0041]

[0042] Among them, NT is the total number of T-shaped road intersection nodes,

[0043] The average road width AW refers to the average road width within the disaster prevention and living circle, and the calculation formula is as follows:

[0044]

[0045] where w i is the width of the i-th road, and N r is the total number of roads,

[0046] The refuge space patch index PI refers to the ratio of the refuge space area to the total area of the disaster prevention and living circle, and the calculation formula is as follows:

[0047]

[0048] where A b refers to the refuge space area,

[0049] The refuge space shape index ESI refers to the degree of deviation of the shape of the disaster prevention and living circle from a square with the same area, and the calculation formula is as follows:

[0050]

[0051] where, taking the square as a reference, C refers to the total perimeter of the refuge space, and A e refers to the total land area of the refuge space.

[0052] In an embodiment of the present invention, in step S5,

[0053] The ten-minute refuge success rate SR t10 refers to the ratio of the number of people who complete refuge within ten minutes to the total number of people, and the calculation formula is as follows:

[0054]

[0055] where P (t＜10) is the number of people who complete refuge within ten minutes, and p is the total number of people taking refuge within the disaster prevention and living circle,

[0056] The total refuge time refers to the time required for all people within the disaster prevention and living circle to complete refuge,

[0057] The congestion mileage ratio D refers to the ratio of the mileage of sections where the pedestrian flow density exceeds 4 people / ㎡ during the entire refuge process to the total length of all roads within the disaster prevention and living circle, and the calculation formula is as follows:

[0058]

[0059] where L ρ＞4 is the mileage of sections where the pedestrian flow density exceeds 4 people / ㎡ during the entire refuge process,

[0060] The congestion time refers to the total time elapsed from the generation of the first congestion point to the complete disappearance of all congestions.

[0061] In an embodiment of the present invention, in step S6,

[0062] The Pearson correlation coefficient is used to analyze the correlation between each morphological parameter and the evacuation accessibility evaluation index. The calculation formula is as follows:

[0063]

[0064] where r is the Pearson correlation coefficient, X i represents the morphological parameter of the i-th sample, is the mean value of the morphological parameter X; Y i represents the evacuation accessibility evaluation index of the i-th sample, is the mean value of the evacuation accessibility evaluation index.

[0065] The method for optimizing the spatial form of a disaster prevention living circle based on evacuation accessibility provided by the present invention has the following beneficial technical effects: more efficiently identifying typical forms of disaster prevention living circles, more accurately and scientifically evaluating evacuation accessibility, and more fully exploring the influence of morphological parameters on evacuation accessibility. The present invention can provide a scientific basis for the government and designers to scientifically optimize the disaster prevention living circle. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0067] Figure 1 is a flowchart of the method for optimizing the spatial form of a disaster prevention living circle based on evacuation accessibility according to an embodiment of the present invention;

[0068] Figure 2 are the ESI values when the shapes of the evacuation spaces are square, regular pentagon, and regular pentagram respectively. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0070] Figure 1 The flowchart of the optimization method for the spatial form of a disaster prevention living circle based on evacuation accessibility according to an embodiment of the present invention is as follows. As Figure 1 shown, the optimization method for the spatial form of a disaster prevention living circle based on evacuation accessibility provided by the present invention includes:

[0071] S1: Extract the quantity and location information of residential-level evacuation spaces in the target city, extract evacuation space samples, obtain the geographical area range where the evacuation space samples are located from the map, and establish a disaster prevention living circle;

[0072] There are often multiple evacuation spaces in a city. The types of evacuation spaces in this embodiment include schools and parks. In other embodiments, it may also include other places that can be used for evacuation. In this step, it is necessary to first obtain the geographical location of each evacuation space, and then use the random sampling survey method to obtain evacuation space samples.

[0073] In actual implementation, a script can be written using a python program, and map data can be batch obtained through the Isochone API interface of the Mapbox website, and the ten-minute walking circle range centered on the sample evacuation space can be crawled to establish a disaster prevention living circle.

[0074] S2: According to the crowd evacuation process from the evacuation starting point to the evacuation road and finally to the evacuation space, calculate the morphological parameters of the evacuation accessibility of the disaster prevention living circle and perform quantification processing. The morphological parameters include evacuation starting point morphological parameters, evacuation road morphological parameters, and evacuation space morphological parameters;

[0075] When the crowd evacuates, it evacuates in the direction of evacuation starting point → evacuation road → evacuation space.

[0076] S3: According to the typical characteristics of the disaster prevention living circle, divide the disaster prevention living circle into multiple categories, and select the disaster prevention living circles in which each morphological parameter is between 20% and 80% in each category of disaster prevention living circle as the evacuation simulation samples;

[0077] In this step, the disaster prevention living circle can be classified by using clustering analysis or other methods. The disaster prevention living circles belonging to the same category have the same typical characteristics, which is helpful for subsequent research.

[0078] S4: Set the crowd parameters and construct an evacuation simulation model of the disaster prevention living circle according to the evacuation simulation samples, and perform crowd evacuation simulation. Setting the crowd parameters includes setting the following items (1) to (4):

[0079] (1) Set the number of people and population density in the neighborhood,

[0080] (2) Set the initial position, end position, and evacuation behavior rules of the crowd,

[0081] (3) Set the gender and age composition of the evacuated population.

[0082] (4) Set the body shape data, initial speed, and walking speed of different genders and age groups.

[0083] S5: Based on the results of the population evacuation simulation, calculate the evaluation indicators of evacuation accessibility. The evaluation indicators of evacuation accessibility include the ten-minute evacuation success rate, the total evacuation time, the proportion of congested mileage, and the congestion time.

[0084] S6: Calculate the correlation degree between the morphological parameters and the evaluation indicators of evacuation accessibility, and extract the morphological parameters that have a positive or negative correlation with evacuation accessibility as the key morphological elements.

[0085] S7: Based on the correlation characteristics between the key morphological elements and evacuation accessibility, optimize the spatial form of the disaster prevention living circle.

[0086] Strengthen the key morphological elements that are positively correlated with evacuation accessibility, and the higher the positive correlation degree, the greater the strengthening intensity; reduce the key morphological elements that are negatively correlated with evacuation accessibility, and the higher the negative correlation degree, the greater the reduction intensity, so as to improve evacuation accessibility.

[0087] In an embodiment of the present invention, in step S2,

[0088] The morphological parameters of the evacuation starting point include the floor area ratio, building density, and density of neighborhood entrances and exits.

[0089] The morphological parameters of the evacuation road include the road density, road network connectivity, intersection density, T-junction rate, and average road width.

[0090] The morphological parameters of the evacuation space include the patch index of the evacuation space and the shape index of the evacuation space.

[0091] The floor area ratio (FAR) refers to the ratio of the total above-ground building area in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0092]

[0093] Where S i is the total building area of the i-th building, A s is the total area of the disaster prevention living circle, and n is the total number of buildings.

[0094] The building density (BD) refers to the ratio of the total base area of all buildings in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0095]

[0096] Where fi is the floor area of the i-th building,

[0097] The neighborhood entrance density DNE refers to the ratio of the number of neighborhood entrances in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0098]

[0099] where N n is the number of neighborhood entrances,

[0100] The road density RD refers to the ratio of the total length of all roads in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0101]

[0102] where R L is the total length of all roads in the disaster prevention living circle,

[0103] The road network connectivity RC refers to the ratio of the number of connection paths of all nodes in the disaster prevention living circle to the total number of nodes. The calculation formula is as follows:

[0104]

[0105] where k i is the number of paths connected to the i-th node, and N I is the total number of nodes,

[0106] The intersection density DI refers to the ratio of the total number of nodes in the disaster prevention living circle to the total area of the disaster prevention living circle. The calculation formula is as follows:

[0107]

[0108] The T-junction rate TR refers to the ratio of the number of T-shaped road intersection nodes to the total number of nodes. The calculation formula is as follows:

[0109]

[0110] where N T is the total number of T-shaped road intersection nodes,

[0111] The average road width AW refers to the average road width in the disaster prevention living circle. The calculation formula is as follows:

[0112]

[0113] where w i is the width of the i-th road, and N r is the total number of roads,

[0114] The refuge space patch index PI refers to the ratio of the area of the refuge space to the total area of the disaster prevention living circle, and the calculation formula is as follows:

[0115]

[0116] Among them, A b refers to the area of the refuge space,

[0117] The refuge space shape index ESI refers to the degree of deviation of the shape of the disaster prevention living circle from that of a square with the same area, and the calculation formula is as follows:

[0118]

[0119] Among them, the refuge space shape index takes the square as a reference object, C refers to the total perimeter of the refuge space, and A e refers to the total land area of the refuge space. When ESI is close to or equal to 1, the shape of the refuge space is infinitely close to a square and the shape is more regular; when the value of ESI is larger, it indicates that it deviates more from the square and the shape is more irregular. As Figure 2 shown are the values of ESI when the shapes of the refuge space are square, regular pentagon, and regular pentagram respectively.

[0120] In an embodiment of the present invention, in step S5,

[0121] The ten-minute refuge success rate SR t10 refers to the ratio of the number of people who complete refuge within ten minutes to the total number of people, and the calculation formula is as follows:

[0122]

[0123] Among them, P (t＜10) is the number of people who complete refuge within ten minutes, and p is the total number of people taking refuge within the disaster prevention living circle,

[0124] The total refuge time refers to the time required for all people in the disaster prevention living circle to complete refuge,

[0125] The congestion mileage ratio D refers to the ratio of the mileage of the sections where the pedestrian flow density during the entire refuge process exceeds 4 people / ㎡ to the total length of all roads within the disaster prevention living circle, and the calculation formula is as follows:

[0126]

[0127] Among them, L ρ＞4 is the mileage of the sections where the pedestrian flow density during the entire refuge process exceeds 4 people / ㎡,

[0128] The congestion time refers to the total time elapsed from the generation of the first congestion point to the complete disappearance of all congestions.

[0129] In an embodiment of the present invention, in step S6,

[0130] The Pearson correlation coefficient is used to analyze the correlation between each morphological parameter and the evacuation accessibility evaluation index. The calculation formula is as follows:

[0131]

[0132] where r is the Pearson correlation coefficient, X i represents the morphological parameter of the i-th sample, is the mean value of the morphological parameter X; Y i represents the evacuation accessibility evaluation index of the i-th sample, is the mean value of the evacuation accessibility evaluation index.

[0133] The Pearson correlation coefficient is a statistic that measures the strength and direction of the linear relationship between two variables. Its value range is: [-1, 1]. The larger the absolute value of the Pearson correlation coefficient, the stronger the correlation, and vice versa, the weaker the correlation. That is, when the r value is close to 1, there is a high positive correlation between the morphological parameter and the evacuation accessibility evaluation index; when the r value is closer to -1, the two show a high negative correlation; when the r value is close to 0, the two have no correlation.

[0134] The method for optimizing the spatial form of the disaster prevention living circle based on evacuation accessibility provided by the present invention has the following beneficial technical effects: more efficiently identifying the typical forms of the disaster prevention living circle, more accurately and scientifically evaluating the evacuation accessibility, and more fully exploring the influence of morphological parameters on the evacuation accessibility. The present invention can provide a scientific basis for the government and designers to scientifically optimize the disaster prevention living circle.

[0135] Those of ordinary skill in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or processes in the drawings are not necessarily essential for implementing the present invention.

[0136] Those of ordinary skill in the art can understand that the modules in the device in the embodiment can be distributed in the device of the embodiment according to the description of the embodiment, or can be correspondingly changed and located in one or more devices different from the present embodiment. The modules of the above embodiment can be combined into one module, or can be further split into multiple sub-modules.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing the spatial form of a disaster prevention living circle based on refuge accessibility, characterized in that: include: S1: Extract the number and location information of the target city's residential area-level shelter space, extract the shelter space sample, obtain the geographical area where the shelter space sample is located from the map, and establish a disaster prevention living circle; S2: According to the crowd evacuation process from the evacuation starting point to the evacuation road and finally to the refuge space, the morphological parameters of the refuge accessibility of the disaster prevention living circle are calculated and quantified. The morphological parameters include the morphological parameters of the evacuation starting point, the evacuation road morphological parameters and the refuge space morphological parameters; S3: According to the typical characteristics of the disaster prevention living circle, the disaster prevention living circle is divided into multiple categories, and the disaster prevention living circles with various morphological parameters between 20% and 80% in each category of disaster prevention living circle are selected as evacuation simulation samples; S4: Setting crowd parameters and constructing a disaster prevention living circle evacuation simulation model based on the evacuation simulation sample to perform crowd evacuation simulation. Setting crowd parameters includes setting the following (1) to (4): (1) Set the number of people in the neighborhood and the density of people. (2) Set the crowd's initial position, final position, and evacuation behavior rules. (3) Set the gender and age composition of the evacuees. (4) Setting the body data, initial speed, and walking speed of people of different genders and ages; S5: Based on the crowd evacuation simulation results, the evacuation accessibility evaluation indicators are calculated. The evacuation accessibility evaluation indicators include the 10-minute evacuation success rate, the total evacuation time, the congestion mileage ratio, and the congestion time; S6: Calculate the correlation between morphological parameters and refuge accessibility assessment indicators, and extract morphological parameters that are positively correlated or negatively correlated with refuge accessibility as key morphological elements; S7: Optimize the spatial form of the disaster prevention living circle based on the correlation characteristics between key morphological elements and shelter accessibility.

2. The method for optimizing the spatial form of a disaster prevention living circle based on evacuation accessibility according to claim 1, characterized in that: In step S1, the refuge space samples are extracted by using a random sampling survey method, and the types of refuge spaces include schools and parks.

3. The method for optimizing the spatial form of a disaster prevention living circle based on refuge accessibility according to claim 1, characterized in that: In step S2, The morphological parameters of the evacuation starting point include volume ratio, building density, and neighborhood entrance and exit density. Evacuation road morphological parameters include road density, road network connectivity, intersection density, T-intersection rate, and average road width. The refuge space morphological parameters include the refuge space patch index and the refuge space shape index. The floor area ratio FAR refers to the ratio of the total area of ​​ground buildings within the disaster prevention living zone to the total area of ​​the disaster prevention living zone. The calculation formula is as follows: Among them, S i is the total floor area of ​​the i-th building, A s is the total area of ​​the disaster prevention living area, n is the total number of buildings, Building density BD refers to the ratio of the total base area of ​​all buildings in the disaster prevention living circle to the total area of ​​the disaster prevention living circle. The calculation formula is as follows: Among them, f i is the area of ​​the i-th building, The neighborhood entrance and exit density DNE refers to the ratio of the number of neighborhood entrances and exits in the disaster prevention living circle to the total area of ​​the disaster prevention living circle. The calculation formula is as follows: Among them, N n is the number of neighborhood entrances and exits, Road density RD refers to the ratio of the total length of all roads in the disaster prevention living circle to the total area of ​​the disaster prevention living circle. The calculation formula is as follows: Among them, R L The total length of all roads within the disaster prevention living area, The road network connectivity RC refers to the ratio of the number of connection paths of all nodes in the disaster prevention living circle to the total number of nodes. The calculation formula is as follows: Among them, k i is the number of paths connected to the i-th node, N I is the total number of nodes, The intersection density DI refers to the ratio of the total number of nodes in the disaster prevention living circle to the total area of ​​the disaster prevention living circle. The calculation formula is as follows: The T-intersection rate TR refers to the ratio of the number of T-shaped road intersection nodes to the total number of nodes. The calculation formula is as follows: Among them, N T is the total number of T-type road intersection nodes, The average road width AW refers to the average road width within the disaster prevention living area, and the calculation formula is as follows: Among them, w i is the width of the ith road, N r is the total amount of roads, The evacuation space patch index PI refers to the ratio of the evacuation space area to the total area of ​​the disaster prevention living circle. The calculation formula is as follows: Among them, A b Refers to the area of ​​​​the refuge space, The ESI (Evacuation Space Shape Index) refers to the degree of deviation of the shape of the disaster prevention living area from a square of the same area. The calculation formula is as follows: Among them, the square is used as the reference, C refers to the total perimeter of the refuge space, A e Refers to the total land area of ​​refuge space.

4. The method for optimizing the spatial form of a disaster prevention living circle based on evacuation accessibility according to claim 3, characterized in that: In step S5, Ten-minute evacuation success rate SR t10 Refers to the ratio of the number of people who have completed evacuation within ten minutes to the total number of people. The calculation formula is as follows: Among them, P (t＜10) is the number of people who evacuated within ten minutes, p is the total number of people evacuated within the disaster prevention living circle, The total evacuation time refers to the time required for all people in the disaster prevention living area to complete the evacuation. The congestion mileage ratio D refers to the ratio of the road section mileage where the passenger flow density exceeds 4 people / ㎡ during the entire evacuation period to the total length of all roads in the disaster prevention living circle. The calculation formula is as follows: Among them, L ρ＞4 For the mileage of road sections where the full-time passenger density exceeds 4 people / ㎡, Congestion time refers to the total time from the emergence of the first congestion point to the complete disappearance of all congestion.

5. The method for optimizing the spatial form of a disaster prevention living circle based on evacuation accessibility according to claim 3, characterized in that: In step S6, The Pearson correlation coefficient was used to analyze the correlation between each morphological parameter and the refuge accessibility evaluation index. The calculation formula is as follows: Among them, r is the Pearson correlation coefficient, X i represents the morphological parameters of the i-th sample, is the mean of the morphological parameters X; Y i represents the refuge accessibility evaluation index of the i-th sample, is the mean value of the refuge accessibility evaluation index.

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